Structure–Activity Relationship Study on Soticlestat Derivatives for the Discovery of CYP46A1 (CH24H) Inhibitors

Xinwei Hu; Wenqian Huang; Xiaotong Lin; Hao Zhang; Yishu Huang; Jiang Wu; Guilong Zhao

doi:10.3390/molecules31030460

. 2026 Jan 28;31(3):460. doi: 10.3390/molecules31030460

Structure–Activity Relationship Study on Soticlestat Derivatives for the Discovery of CYP46A1 (CH24H) Inhibitors

Xinwei Hu ^1,^2,^†, Wenqian Huang ^2,^3,^4,^†, Xiaotong Lin ², Hao Zhang ^2,^3,⁴, Yishu Huang ^2,^3,⁴, Jiang Wu ^5,^*, Guilong Zhao ^1,^2,^3,^4,^*

Editor: Mª Ángeles Castro

PMCID: PMC12899276 PMID: 41683437

Abstract

Dravet syndrome (DS) and Lennox–Gastaut syndrome (LGS) are rare, severe developmental and epileptic encephalopathies with poor prognosis, and novel drugs are urgently needed to meet clinical needs. CYP46A1 (cholesterol 24-hydroxylase, CH24H) is mainly responsible for the metabolism of cholesterol to 24(S)-hydroxycholesterol in the brain and is implicated in many brain disorders through the mediation of excitatory amino acid transporter 2 (EAAT2) and N-methyl-D-aspartate (NMDA) receptors. Inhibition of CYP46A1 is supposed to provide a novel treatment for disorders associated with neural hyperexcitation, such as epilepsy and epileptic syndromes. Soticlestat, a potent CYP46A1 inhibitor being developed by Takeda, is indicated for LGS and DS but suffers from unsatisfactory in vivo potency in animal models and clinical trials. We designed three series of soticlestat derivatives to explore the structure–activity relationship (SAR) with the aim of finding more potent CYP46A1 inhibitors and understanding the SAR of CYP46A1 inhibitors represented by soticlestat. Eventually, three compounds with a benzenesulfonamide moiety (in subseries C-4) that serves as an isostere of OH in soticlestat were discovered with very potent CYP46A1 inhibitory activities comparable to soticlestat, and an interesting flat SAR profile was observed in some subseries. The findings in the present study provide insight into the SAR of CYP46A1 inhibitors and should be valuable for the future design of novel CYP46A1 inhibitors.

Keywords: CH24H, CYP46A1, soticlestat, structure-activity relationship, Dravet syndrome, Lennox-Gastaut syndrome

1. Introduction

Dravet syndrome (DS) and Lennox–Gastaut syndrome (LGS) belong to rare, severe developmental and epileptic encephalopathies (DEEs), which are characterized by early-onset treatment-resistant seizures, cognitive and behavioral impairment, poor prognosis, and high mortality rates [1,2,3]. Advances have been made over the past few decades in the development of pharmacological and non-pharmacological therapies for DS and LGS, such as clobazam, fenfluramine, stiripentol, cannabidiol, the ketogenic diet, and emerging therapies targeting DNA and RNA regulation; however, there are still urgent clinical needs for novel drugs due to low response rates and severe adverse effects associated with current therapies [4,5,6].

Cholesterol is an important structural and functional component in the brain. After de novo synthesis in the brain, cholesterol is metabolized to 24(S)-hydroxycholesterol, which then crosses the blood–brain barrier (BBB) to enter the circulation and is delivered to the liver for further degradation [7]. The main enzyme responsible for the metabolism of cholesterol is cholesterol 24-hydroxylase (CH24H), also known as cholesterol 24S-hydroxylase or CYP46A1. CYP46A1 is predominantly expressed in the brain and is a crucial enzyme in brain cholesterol homeostasis. It is implicated in many neurological functions by regulating the level of 24(S)-hydroxycholesterol in the brain and is thus emerging as a novel promising therapeutic target for the treatment of a lot of brain disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HTD) [8,9,10]. Under certain pathological conditions, CYP46A1 is upregulated and disrupts the glutamate transporter excitatory amino acid transporter 2 (EAAT2) [11], thereby impairing glutamate uptake function; in addition, 24(S)-hydroxycholesterol is a positive allosteric modulator of N-methyl-D-aspartate (NMDA) receptors, an important class of excitatory receptors in the brain [12]. Increased levels of extracellular glutamate arising from EAAT2 disruption and NMDA receptor activation by 24(S)-hydroxycholesterol can cause glutamate-evoked neuronal excitotoxicity. Therefore, CYP46A1 inhibitors are supposed to suppress neuronal excitotoxicity present in CYP46A1 pathological conditions and provide a novel treatment for disorders associated with neural hyperexcitation, such as epilepsy and epileptic syndromes.

Takeda Pharmaceuticals Company has been developing soticlestat (TAK-935, OV-935), a potent CYP46A1 inhibitor, for the treatment of LGS and DS (Figure 1) [13,14]. However, it suffers from unsatisfactory in vivo potency in animals and clinical trials. In a preclinical study, soticlestat reduced seizures by only 42% and lowered brain 24(S)-hydroxycholesterol levels by only 55% at 30 mg/kg (po), a dose associated with near-maximal efficacy [15]. In major clinical trials, soticlestat, at doses of up to 600 mg/day, did not show significantly higher efficacy in reducing convulsive seizures in patients with LGS, although such significance was observed in patients with DS [14]. Encouraged by these aforementioned shortcomings, we initiated a program aiming to find more potent CYP46A1 inhibitors based on soticlestat as a chemical template. A total of three series with 85 derivatives were designed through the modification of the distal pyridine ring in soticlestat (Series A), modification of the linker connecting the bipyridine and piperidine ring in soticlestat (Series B), and replacement of the hydroxyl group in soticlestat using a bioisosterism strategy (Series C, further categorized into four subseries, C-1, C-2, C-3, and C-4). These compounds were evaluated for in vitro CYP46A1 inhibitory activity, and some CYP46A1 inhibitors with potent inhibitory activities (IC₅₀) comparable to that of soticlestat were discovered (Figure 1). These findings should be valuable for the future design of novel CYP46A1 inhibitors.

Chemical modifications based on soticlestat in the present study.

2. Results and Discussion

2.1. Chemistry

The synthetic routes to two key intermediates 3 and 7 (both as trifluoroacetic acid (TFA) salts) are shown in Scheme 1. Commercially available ketone 1 was treated with BnMgCl to give tertiary alcohol 2, and the Boc protecting group in the latter was then cleaved by TFA to give 3 as a TFA salt. On the other hand, treatment of commercially available carboxylic acid 4 with (COCl)₂ in the presence of a catalytic amount of N,N-dimethylformamide (DMF) afforded the corresponding carbonyl chloride, which was subsequently treated with t-BuOK to give the corresponding tert-butyl ester. Suzuki coupling of 5 and pyridine-4-boronic acid in the presence of Pd(PPh₃)₄ as a catalyst and Na₂CO₃ as a base in refluxing DME (1,2-dimethoxyethane)/H₂O produced bipyridine 6. Cleavage of the tert-butyl ester moiety with TFA gave the corresponding carboxylic acid 7 as a TFA salt.

The synthetic routes to target compounds A1 and A2 are shown in Scheme 2. Suzuki coupling of 5 and 4-nitrophenylboronic acid under the same conditions used above produced 8. The tert-butyl ester functionality in 8 was converted to the corresponding methyl ester functionality in 9 by cleavage with TFA followed by acid-catalyzed esterification of the carboxylic acid intermediate in refluxing MeOH. Pd-catalyzed hydrogenolysis of NO₂ in 9 at atmospheric pressure and room temperature smoothly afforded aniline 10, which was subjected to a Sandmeyer reaction to give iodobenzene 11. CuI/PdCl₂(PPh₃)₂-mediated Sonogashira coupling of 11 and trimethylsilylacetylene furnished 12, which was treated with tetra-n-butylammonium fluoride (TBAF) to remove the trimethylsilyl (TMS) protecting group to give 13. NaOH-mediated saponification of methyl ester 13 followed by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI)/1-hydroxybenzotriazole (HOBT)-mediated amide formation with 3·TFA produced target compound A1 [16,17]. Pd-mediated cross-coupling of 11 with dimethylphosphine oxide in the presence of Pd₂(dba)₃/Xantphos afforded 15 [18], which was converted to target compound A1 by a procedure identical to that used for the synthesis of A1 from 13.

The synthetic route to A3 is shown in Scheme 3. Sonogashira coupling of commercially available 17 and trimethylsilylacetylene under the same conditions described above gave 18, which was converted to target compound A3 following the same procedure used for the synthesis of A1 from 12.

The synthetic routes to target compounds A4 and A5 are shown in Scheme 4. Treatment of 4 with (COCl)₂ in the presence of a catalytic amount of DMF afforded the corresponding carbonyl chloride, which was reacted with 3·TFA in the presence of Et₃N to give amide 21. Suzuki coupling of 21 and boronic acid 22 under the same conditions used above produced 24, which was heated with (NH₄)₂S in the presence of Et₃N in pyridine at 50 °C to give target compound A4 [19]. Suzuki coupling of 21 and boronic acid 23 under the same conditions above produced target compound A5.

The synthetic route to target compound A6 is depicted in Scheme 5. Suzuki coupling of 5 and boronic acid 25 under the same conditions used above produced 26. The amide moiety in 26 was transformed into the corresponding thioamide with Lawesson reagent in refluxing toluene to give 27 [20], which was further converted to target compound A6 by the same procedure used for the synthesis of A1 from 14.

The synthetic route to target compound A7 is shown in Scheme 6. Treatment of commercially available thiophenol 28 with t-BuCl in the presence of anhydrous AlCl₃ produced thioether 29 [21]. Lithiation of phenyl bromide 29 by treatment with n-BuLi at −78 °C followed by trapping of the phenyl cabanion with B(OMe)₃ afforded phenyl boronic acid 30. Suzuki coupling of 30 and 5 under the same conditions described above gave 31, which was converted to target compound A7 by the same procedure used for the synthesis of A6 from 27.

The synthetic route to target compound A8 is outlined in Scheme 7. Hydrogenolysis of nitrobenzene 8 to aniline 32 was achieved under the same conditions described above, and the latter was transformed into thiourea 34 by initial treatment with CSCl₂ to give isothiocyanate 33 and subsequent treatment with dimethylamine. Cleavage of the tert-butyl ester moiety with TFA followed by treatment with HCl in MeOH generated in situ by SOCl₂ in MeOH gave 35 as an HCl salt. EDCI/HOBT-mediated amide formation of 35 and 3·TFA under the same conditions described above produced target compound A8.

The synthetic route to target compounds B1 and B2 is shown in Scheme 8. Suzuki coupling of commercially available 36 and pyridine-4-boronic acid afforded 37 under the same conditions used above. Treatment of fluoropyridine 37 with Na₂S in the presence of K₂CO₃ in DMF at 120 °C led to the formation of thiophenol 38 via aromatic nucleophilic substitution. Substitution reaction of 38 with tert-butyl 2-bromo-2-methylpropanoate in the presence of K₂CO₃ in DMF at 45 °C gave 39, which was converted to target compound B1 by the same procedure described above. Oxidation of thioether B1 to the corresponding sulfone B2 was achieved by treatment with m-chloroperoxybenzoic acid (mCPBA) in CH₂Cl₂ at room temperature.

The synthetic routes to target compounds B3 and B4 are shown in Scheme 9. Suzuki coupling of commercially available 41 and pyridine-4-boronic acid afforded 42 under the same conditions used above. The amine 42 was converted to isothiocyanate 43 by treatment with CSCl₂ as described above. Treatment of 43 with 3·TFA in the presence of Et₃N afforded target compound B3. Treatment of amine 42 with phenyl chloroformate in the presence of pyridine gave benzyl carbamate 44, which was subsequently treated with 3·TFA in the presence of Et₃N to produce target compound B4.

The synthetic route to target compound B5 is shown in Scheme 10. Suzuki coupling of commercially available 45 and pyridine-4-boronic acid, as described above, afforded 46. Aldehyde 46 was treated with hydroxylamine to give oxime 47, which was then reduced to primary amine 48 with zinc powder in the presence of AcONH₄ and aqueous ammonia in refluxing MeCN. Treatment of 48 with phenyl chloroformate followed by reaction with 3·TFA produced B5 by the same procedure described above.

The synthetic routes to target compounds B6 and B7 are shown in Scheme 11. Aldehyde 45 was reduced by NaBH₄ to the corresponding primary alcohol 50, and the latter was subsequently converted to the corresponding bromide 51 by treatment with PBr₃ in refluxing CH₂Cl₂. TBAF-mediated substitution of 51 with TMSCN afforded nitrile 52. Suzuki coupling of 52 and pyridine-4-boronic acid under the same conditions described above gave 53. Acidic hydrolysis of nitrile 53 with H₂SO₄ in refluxing aqueous acetic acid gave corresponding carboxylic acid, which was then esterified to the corresponding methyl ester 54 in refluxing HCl/MeOH. Deprotonation of 54 with excess lithium bis(trimethylsilyl)amide (LiHMDS) followed by gem-dimethylation with excess MeI produced gem-dimethylated ester 55 [22]. Saponification of 55 with NaOH led to the corresponding acid 56, which was converted to target compound B6 by a procedure identical to that used for the synthesis of 21 from 4. Deprotonation of 54 with excess LiHMDS followed by treatment with 1,3,2-dixoathiolane 2,2-dioxide produced a cyclopropane counterpart 57 [23], which was converted to target compound B7 following the same procedure used for B6.

The synthetic routes to target compounds B8–B11 are shown in Scheme 12 and Scheme 13. The experimental details have been published in our earlier work [24].

The synthetic routes to target compounds C-1-1 to C-1-3 and C-2-1 to C-2-8 are shown in Scheme 14. Deprotonation of commercially available 67 with lithium diisopropylamide (LDA) at −78 °C followed by benzylation with BnBr afforded 68, which then gave rise to amide 69 upon treatment with H₂O₂/K₂CO₃ in DMSO [25]. Phenyliodine (III) bis(trifluoroacetate) (PIFA)-mediated Hofmann rearrangement of amide 69 in MeCN/H₂O at room temperature smoothly led to the formation of tertiary amine 70 [26]. Reactions of amine 70 with sulfonyl chlorides or anhydrides produced sulfonamides 71-1 to 71-3, while reactions with carbonyl chlorides or anhydrides produced amides 72-1 to 72-8. Cleavage of Boc in 71-1 to 71-3 and 72-1 to 72-8 followed by EDCI/HOBT-mediated amide formation with 7·TFA, as described above, gave target compounds C-1-1 to C-1-3 and C-2-1 to C-2-8, respectively.

The synthetic route to target compounds C-3-1 to C-3-6 is shown in Scheme 15. Nitrile 68 was reduced with NaBH₄ mediated by NiCl₂·6H₂O in MeOH to give primary amine 73, which was converted to amides 74-1 to 74-6 by the same procedure described above for 72-1 to 72-8. Cleavage of Boc in 74-1 to 74-6 followed by EDCI/HOBT-mediated amide formation with 7·TFA, using the same procedure as above, led to the formation of target compounds C-3-1 to C-3-6.

The synthetic route to target compounds C-4-1 to C-4-45 is shown in Scheme 16. Primary amine 73 was converted to C-4-1 to C-4-45 by a procedure identical to that used for C-3-1 to C-3-6, as discussed above.

The synthetic routes to target compounds C-4-46 to C-4-49 are shown in Scheme 17. C-4-12 was reduced to C-4-46 by Pd-catalyzed hydrogenolysis under the same condition used above. Saponification of the ester moiety in 76 with aqueous NaOH in MeOH led to the formation of C-4-47, while reduction of 76 with LiAlH₄ produced C-4-48. Reduction of 75-47 by Pd-catalyzed hydrogenolysis gave aniline 77, which was acylated with AcCl in the presence of Et₃N to afford 78. Compound 78 was converted to target compound C-4-49 by the identical procedure used above.

It should be noted that all target compounds in Series A and Series C in the present study exhibited unusual NMR characteristics because there are four stable conformations at room temperature, which exist as two diastereomers, each as a pair of enantiomers, due to restricted bond rotations around two axes, i.e., the amide CO-N and CO-pyridine. This phenomenon has been intensively investigated by variable-temperature ¹³C NMR, molecular mechanics, and quantum mechanics in our earlier study [24], and will not be further discussed here.

2.2. In Vitro CYP46A1 Inhibition

The in vitro CYP46A1 inhibitory activity of the target compounds was determined by the inhibition of CYP46A1-mediated metabolism of testosterone to 16β-hydroxyltestosterone by the compounds tested and expressed as the half-maximal inhibitory concentration (IC₅₀) using soticlestat as a positive control [27]. The results are summarized in Table 1.

Table 1.

In vitro CYP46A1 inhibitory activity (IC₅₀) of target compounds A1–A8, B1–B11, C-1-1 to C-1-3, C-2-1 to C-2-8, C-3-1 to C-3-6, and C-4-1 to C-4-49.

Compound	IC₅₀ (nM)	Compd	IC₅₀ (nM)	Compd	IC₅₀ (nM)	Compd	IC₅₀ (nM)
Soticlestat	18.0	C-1-3	296.3	C-4-8	41.8	C-4-30	36.47
A1	>10,000	C-2-1	3562	C-4-9	36.2	C-4-31	56.13
A2	>10,000	C-2-2	>10,000	C-4-10	79.4	C-4-32	25.7
A3	>10,000	C-2-3	>10,000	C-4-11	113.2	C-4-33	82.3
A4	>10,000	C-2-4	>10,000	C-4-12	168.6	C-4-34	32.5
A5	>10,000	C-2-5	5900	C-4-13	63.76	C-4-35	371.4
A6	>10,000	C-2-6	4346	C-4-14	117.3	C-4-36	51.2
A7	>10,000	C-2-7	111.8	C-4-15	63.02	C-4-37	24.2
A8	>10,000	C-2-8	>10,000	C-4-16	54.49	C-4-38	13.6
B1	3375	C-3-1	>10,000	C-4-17	17.35	C-4-39	117.7
B2	>10,000	C-3-2	2193	C-4-18	56.15	C-4-40	63.0
B3	1023	C-3-3	226.7	C-4-19	65.67	C-4-41	17.4
B4	>10,000	C-3-4	156.1	C-4-20	50.92	C-4-42	48.6
B5	>10,000	C-3-5	1634	C-4-21	41.7	C-4-43	127.5
B6	>10,000	C-3-6	372.6	C-4-22	43.99	C-4-44	150.6
B7	>10,000	C-4-1	526.9	C-4-23	62.05	C-4-45	317.9
B8	>10,000	C-4-2	151.5	C-4-24	56.38	C-4-46	147.4
B9	>10,000	C-4-3	1849	C-4-25	52.68	C-4-47	3240
B10	140.9	C-4-4	982.6	C-4-26	74.22	C-4-48	379.5
B11	>10,000	C-4-5	133	C-4-27	27.5	C-4-49	166.1
C-1-1	102	C-4-6	126.1	C-4-28	41.23
C-1-2	5583	C-4-7	526.3	C-4-29	33.31

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As shown in Figure 1, Series A focuses on the modification of the distal pyridine ring in soticlestat with the aim of finding a moiety that can bind to the heme iron in CYP46A1 with higher affinity, because the N in the distal pyridine ring in soticlestat was believed to be a critical moiety for ligation to the CYP46A1 heme iron [13]. Unfortunately, among all the moieties screened in A1–A8, none were superior to the distal pyridine N atom in soticlestat; in fact, all modifications led to complete loss of CYP46A1 inhibition (IC₅₀ values > 10,000 nM).

Series B focuses on modification of the linker connecting the bipyridine and piperidine rings, which is C=O in soticlestat. Thus, all linkers in B1–B11 were associated with weaker CYP46A1 inhibitory activity than soticlestat, and the most potent one was B10 (IC₅₀ = 140.9 nM), with a CH₂ linker compared to the C=O linker in soticlestat (IC₅₀ = 18.0 nM). It should be noted that the orientation of the distal pyridine N is very important, as indicated by the dramatic difference in CYP46A1 inhibitory activity between B10 (IC₅₀ = 140.9 nM) and B11 (IC₅₀ > 10,000 nM).

Series C focuses on modification of the hydroxyl group in soticlestat using a bioisosterism strategy and is further categorized into four subseries, i.e., C-1, C-2, C-3, and C-4. Series C-1 included three compounds designed by replacement of the OH group in soticlestat with RSO₂NH; however, none of them showed stronger CYP46A1 inhibitory activity than parent soticlestat, with the most potent one being C-1-1, with an IC₅₀ of 102 nM. In Series C-2, the OH in soticlestat was replaced by RCONH and eight compounds were designed; like Series C-1, none of them were stronger than soticlestat, and the most potent one was C-2-7, with an IC₅₀ of 111.8 nM. The same result was obtained in Series C-3, where the OH in soticlestat was replaced by RCONHCH₂ and six compounds were designed, with the most potent one being C-3-4, with an IC₅₀ of 156.1 nM. In Series C-4, we introduced RSO₂NHCH₂ to replace the OH in soticlestat. Four small alkyl substituents (the “R” in RSO₂NHCH₂) were initially introduced in RSO₂NHCH₂ to explore the space (C-4-1 to C-4-4), but all of them were associated with a dramatic decrease in activity. Four different types of aromatic substituents were then introduced (C-4-5 to C-4-8), and fortunately, when R = benzene ring, the CYP46A1 inhibitory activity was only slightly less potent than that of soticlestat (IC₅₀ = 41.8 nM for C-4-8 vs. 18.0 for soticlestat). Inspired by this encouraging observation, some electron-withdrawing and electron-donating groups were then explored by attaching them to the benzene ring (C-4-9 to C-4-13), and it turned out that F, CN, and Cl were associated with potent activity, whereas MeO and NO₂ had opposite effects. Based on this, a large number of derivatives with PhSO₂NHCH₂, where the Ph ring was substituted with F, Cl, CN, CF₃, OCF₃,and their various combinations, were further designed (C-4-14 to C-4-31), which also included two derivatives in which the benzene ring was substituted with bulky alkyl groups, i.e., pentamethyl (C-4-17) and 4-tert-butyl (C-4-27), and the results showed that the SAR exhibited a flat profile, as indicated by the observation that CYP46A1 inhibitory activity did not change significantly with structural modification in these compounds, and most of them exhibited very potent CYP46A1 inhibitory activity with IC₅₀ < 100 nM. However, among them, the two most potent compounds had the Ph ring substituted with pentamethyl (C-4-17, IC₅₀ = 17.35 nM) and 4-tert-butyl (C-4-27, IC₅₀ = 27.5 nM), although many other counterparts substituted with multiple halogens also exhibited IC₅₀ values of < 50 nM. Inspired by this surprising result, we turned to further design many compounds with PhSO₂NHCH₂ where the Ph ring was substituted with a variety of alkyl groups (C-4-32 to C-4-34 and C-4-36 to C-4-43). The assay results showed that a similar flat SAR was observed, with all alkyl-substituted compounds being very potent (IC₅₀ < 100 nM), and two compounds exhibited CYP46A1 inhibitory activity slightly more potent than soticlestat (IC₅₀ = 13.6 nM for C-4-38 and 17.4 nM for C-4-41 vs. 18.0 nM for soticlestat). Notably, in subseries C-4, the introduction of hydrophilic substituents to the benzene ring led to a dramatic decrease in activity (C-4-35 and C-4-44 to C-4-49).

2.3. In Vitro Inhibitory Activities of Target Compounds Against CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4

In order to evaluate the off-target inhibition of compounds in the present study against other CYP enzymes, four potent compounds, C-4-9, C-4-32, C-4-38, and C-4-41, were selected to test their inhibition against five main CYP enzymes, CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5. As shown in Table 2, all four selected compounds displayed weak inhibitory activities against CYP1A2, with IC₅₀ values > 50 μM and high selectivities > 1000, and moderate inhibitory activities against CYP2C9, 2C19, and 2D6, with IC₅₀ values of 1.54–14.7 μM and moderate selectivities of 80–406. However, these four compounds showed strong CYP3A4/5 inhibitory activities (IC₅₀ values = 0.0402 to 0.403 μM), which led to low selectivities ranging from 3.0 to 11. The exact reason or chemical moieties responsible for the strong inhibition against CYP3A4/5 are unknown, since CYP3A4/5 enzymes are known to be associated with broad substrate specificity encompassing a wide range of chemical structures. However, this poor selectivity will be optimized in future work to minimize the potential for drug–drug interactions, since CYP3A4/5 is a predominant drug-metabolizing enzyme for both antiepileptic drugs and many other drugs.

Table 2.

Inhibitory activities of selected compounds C-4-9, C-4-32, C-4-38, and C-4-41 against off-target CYP enzymes (1A2, 2C9, 2C19, 2D6, and 3A4/5).

Compd	1A2		2C9		2C19		2D6		3A4/5
Compd	IC₅₀ (μM)	SR ^a	IC₅₀ (μM)	SR ^a	IC₅₀ (μM)	SR ^a	IC₅₀ (μM)	SR ^a	IC₅₀ (μM)	SR ^a
C-4-9	>50	>1381	6.29	173	14.7	406	2.90	80	0.403	11
C-4-32	>50	>1946	4.27	166	3.34	130	5.81	226	0.0948	3.7
C-4-38	>50	>3676	1.85	136	1.54	113	4.04	297	0.0402	3.0
C-4-41	>50	>2874	5.20	299	4.59	264	2.95	170	0.0898	5.2

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^a SR = selectivity ratio = IC₅₀ (off-target CYP)/IC₅₀ (CYP46A1).

3. Materials and Methods

3.1. Chemistry

Unless stated otherwise, all chemical reagents were obtained commercially and used without further purification. All dried solvents were prepared by standard methods. Reaction progress was monitored by thin-layer chromatography (TLC) on commercially available precoated TLC silica gel plates or by liquid chromatography–mass spectrometry (LC-MS), and separation and purification by flash column chromatography were performed on silica gel columns (200–300 mesh) eluting with EtOAc/petroleum ether (PE) or MeOH/CH₂Cl₂ (as v/v). Melting points were measured in open capillaries with an SGW X-4A microscopic melting point apparatus (Shanghai INESA Physico-Optical Instrument Co., Ltd., Shanghai, China) and are uncorrected. NMR spectra were recorded on Bruker Ascend 500, 600, or 800 NMR spectrometers (Bruker Switzerland AG, Fällanden, Switzerland) using CDCl₃, DMSO-d₆, or CD₃OD as solvent and TMS (for ¹H NMR) or the known carbon chemical shifts in deuterated solvents (for ¹³C NMR) as internal standards. High-resolution mass spectra (HR-MS) were determined with a Thermo Scientific Exactive Plus mass spectrometer (Thermo Fisher Scientific, Bremen, Germany) using electrospray ionization (ESI) and Orbitrap techniques. Unless stated otherwise, evaporation on a rotary evaporator was conducted at temperatures below 40 °C.

The copies of ¹H NMR, ¹³C NMR, ¹⁹F NMR, ³¹P NMR and HR-MS spectra of the synthesized intermediates and target compounds can be seen in Supplementary Materials.

Synthesis of tert-butyl 4-benzyl-4-hydroxypiperidine-1-carboxylate (2). To a stirred solution of 1 (3.00 g, 15.1 mmol) in dried THF (30 mL), cooled at 0 °C under N₂, a solution of BnMgCl in THF(11.3 mL, 18.1 mmol, 1.6 M in THF) was added dropwise. After addition, the reaction mixture was stirred at room temperature overnight. TLC analysis indicated completion of the reaction, after which the mixture was poured into ice–water (50 mL). The resulting mixture was extracted with EtOAc (100 mL × 3), and the combined extracts were washed successively with 0.1 M HCl (100 mL) and brine (100 mL), dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/3, by v/v) to give 2 as a pale yellow oil, 2.10 g (48%). ¹H NMR (500 MHz, CDCl₃) δ 7.34–7.31 (m, 2H), 7.28–7.25 (m, 1H), 7.20–7.18 (m, 2H), 3.87–3.83 (m, 2H), 3.12–3.07 (m, 2H), 2.76 (s, 2H), 1.63–1.57 (m, 2H), 1.51–1.49 (m, 2H), 1.46 (s, 9H). The ¹H NMR data were consistent with those reported in the literature [28].

Synthesis of 4-benzylpiperidin-4-ol trifluoroacetic acid salt (3·TFA). To a stirred solution of 2 (6.30 g, 21.6 mmol) in CH₂Cl₂ (63 mL), cooled to 0 °C, TFA was added (31.5 mL). After addition, the reaction mixture was stirred at room temperature overnight. TLC analysis indicated completion of the reaction, and the mixture was evaporated on a rotary evaporator to dryness to give crude 3 as the trifluoroacetic acid salt. The crude 3 was used directly in the next step without further purification or characterization.

Synthesis of tert-butyl 2-chloronicotinate (5). To a stirred solution of 4 (10.00 g, 63.5 mmol) in dried CH₂Cl₂ (100 mL) in a 250 mL round-bottomed flask equipped with a drying tube fitted with anhydrous CaCl₂ and cooled at 0 °C, (COCl)₂ (16.1 g, 127 mmol) was added dropwise, followed by addition of DMF (three drops). The reaction mixture was thus stirred at room temperature until completion, as indicated by TLC analysis (typically within 2–3 h). The reaction mixture was evaporated on a rotary evaporator to remove all volatiles, and the residue thus obtained was dissolved in dried THF (100 mL). The resulting solution was cooled to −10 °C, and a solution of t-BuOK in THF (152.4 mL, 152.4 mmol, 1.0 M in THF) was added dropwise. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction. Saturated aqueous NaHCO₃ was added dropwise to the reaction mixture (100 mL), and the resulting mixture was extracted with CH₂Cl₂ (150 mL × 3). The combined extracts were washed with brine (100 mL), dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/5, by v/v) to give 5 as a pale yellow oil, 8.20 g (60%). ¹H NMR (500 MHz, CDCl₃) δ 8.48 (dd, J = 2.3 Hz and 4.8 Hz, 1H), 8.07 (dd, J = 2.0 Hz and 7.5 Hz, 1H), 7.34–7.31 (m, 1H), 1.62 (s, 9H). The ¹H NMR data were consistent with those reported in the literature [29].

Synthesis of tert-butyl [2,4′-bipyridine]-3-carboxylate (6). A mixture of 5 (15.00 g, 70.2 mmol), pyridine-4-boronic acid (10.34 g, 84.2 mmol), Pd(PPh₃)₄ (2.43 g, 2.10 mmol), and Na₂CO₃ (23.2 g, 210.6 mmol) in a mixed solvent of DME (100 mL) and water (100 mL) was refluxed under N₂ overnight until TLC analysis indicated completion of the reaction. After cooling to room temperature, the reaction mixture was diluted with water (100 ml) and extracted with EtOAc (150 mL × 3). The combined extracts were washed with brine (100 mL), dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/1, by v/v) to give 6 as a pale yellow solid, 9.00 g (50%). m.p. 78.1–79.9 °C. ¹H NMR (500 MHz, CDCl₃) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.72 (dd, J = 1.8 Hz and 4.3 Hz, 2H), 8.17 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.44 (dd, J = 1.5 Hz and 8.0 Hz, 2H), 7.42 (t, J = 4.0 Hz, 1H), 1.32 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 165.78, 156.09, 150.90, 149.26, 148.10, 137.96, 128.49, 123.16, 122.54, 82.47, 27.28; ESI-HR-MS: (m/z) calcd. for C₁₅H₁₇N₂O₂ ([M+H]⁺) 257.1285, found 257.1289.

Synthesis of [2,4′-bipyridine]-3-carboxylic acid trifluoroacetic acid salt (7·TFA). Following the procedure for the synthesis of 3·TFA from 2, 7·TFA was synthesized from 6 (5.00 g, 19.5 mmol) in CH₂Cl₂ (15 mL) and TFA (25 mL) at room temperature. After evaporation of all volatiles on a rotary evaporator, the residue was triturated with THF (30 mL) to afford 7·TFA (4.92 g). The sample was used directly in the next step without characterization.

Synthesis of tert-butyl 2-(4-nitrophenyl)nicotinate (8). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 8 was prepared from 5 (2.00 g, 9.36 mmol) and 4-nitrophenylboronic acid (1.87 g, 11.2 mmol) in the presence of Pd(PPh₃)₄ (0.33 g, 0.281 mmol) and Na₂CO₃ (2.98 g, 28.1 mmol) in a refluxing mixture of DME/H₂O (20 mL/20 mL) under N₂. Product 8 was isolated and purified by column chromatography (EtOAc/PE = 1/5, by v/v). Pale yellow solid, 2.42 g (86%). m.p. 112.9–113.8 °C. ¹H NMR (500 MHz, CDCl₃) δ 8.78 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.32 (d, J = 8.5 Hz, 1H), 8.19 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.70 (d, J = 8.5 Hz, 1H), 7.44 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 1.34 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 166.16, 156.76, 151.27, 147.86, 147.16, 138.43, 129.91, 128.91, 123.35, 122.88, 83.00, 27.77; ESI-HR-MS: (m/z) calcd. for C₁₆H₁₇N₂O₄ ([M+H]⁺) 301.1183, found 301.1182.

Synthesis of methyl 2-(4-nitrophenyl)nicotinate (9). To a stirred solution of 8 (1.00 g, 3.33 mmol) in CH₂Cl₂ (3 mL), cooled to 0 °C, TFA was added dropwise (5 mL). After addition, the reaction mixture was stirred at room temperature overnight. TLC analysis indicated completion of the reaction, and the mixture was subsequently evaporated to dryness on a rotary evaporator. The residue was dissolved in MeOH (10 mL) and the resulting mixture was cooled to 0 °C, followed by dropwise addition of SOCl₂ (1.3 mL). The reaction mixture was refluxed under N₂ until completion, as indicated by TLC analysis (typically within 4 h). After cooling to room temperature, the reaction mixture was poured into saturated aqueous NaHCO₃ (50 mL) and extracted with EtOAc (50 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a solid, which was triturated with n-hexane to give 9. White solid, 0.65 g (76%). m.p. 113.3–113.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.87 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.32–8.30 (m, 2H), 8.27 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.78–7.76 (m, 2H), 7.63 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 3.67 (s, 3H). The ¹H NMR data were consistent with those reported in the literature [30].

Synthesis of methyl 2-(4-aminophenyl)nicotinate (10). A suspension of 9 (0.30 g, 1.16 mmol) and 10% Pd/C (30 mg) in MeOH (3 mL) was subjected to standard procedure of hydrogenation at atmospheric pressure (balloon) and room temperature overnight until TLC analysis indicated completion of the reaction. The reaction mixture was filtered through Celite and the filtrate was poured into water (20 mL). The resulting mixture was extracted with EtOAc (30 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/3, by v/v) to give 10. Pale yellow solid, 0.20 g (75%). m.p. 107.8–108.6 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.67 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 7.95 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.31 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 7.25 (d, J = 8.5 Hz, 2H), 6.60 (d, J = 8.5 Hz, 2H), 3.70 (s, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 169.36, 158.25, 151.03, 147.47, 137.67, 129.85, 129.65, 126.26, 120.47, 114.58, 52.31; ESI-HR-MS: (m/z) calcd. for C₁₃H₁₃N₂O₂ ([M+H]⁺) 229.0972, found 229.0971.

Synthesis of methyl 2-(4-iodophenyl)nicotinate (11). To stirred concentrated HCl (2.5 mL) at 0 °C, 10 was added (1.00 g, 4.38 mmol) in portions, followed by the addition of water (2.5 mL). A solution of NaNO₂ (0.36 g, 5.26 mmol) in a minimum amount of water was added dropwise. After that, stirring was continued for 15 min at this temperature, followed by dropwise addition of a solution of KI (1.45 g, 8.76 mmol) in a minimum amount of water. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, then poured into water (30 mL). The resulting mixture was brought to pH = 8–9 and extracted with EtOAc (50 mL × 3). The combined extracts were washed successively with 10% Na₂S₂O₃ (50 mL) and brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/3, by v/v) to give 11. Pale yellow oil, 0.65 g (44%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.80 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.15 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.84–7.81 (m, 2H), 7.53 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 7.32–7.29 (m, 2H), 3.69 (s, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 168.04, 157.78, 151.47, 139.50, 138.11, 137.23, 130.38, 126.63, 121.88, 95.16, 52.49; ESI-HR-MS: (m/z) calcd. for C₁₃H₁₁INO₂ ([M+H]⁺) 339.9829, found 339.9833.

Synthesis of methyl 2-(4-((trimethylsilyl)ethynyl)phenyl)nicotinate (12). A mixture of 11 (1.50 g, 4.42 mmol), trimethylsilylacetylene (1.41 g, 14.4 mmol), CuI (42.0 mg, 0.719 mmol), PdCl₂(PPh₃)₂ (0.47 g, 0.663 mmol), and Et₃N (6 mL, 43.5 mmol) in dried THF (15 mL) was stirred at room temperature under N₂ until TLC analysis indicated the completion of reaction. The reaction mixture was poured into water (30 mL) and extracted with EtOAc (50 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/3, by v/v) to give 12. Black oil, 1.00 g (73%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.81 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.16 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.55 (s, 1H), 7.54–7.52 (m, 2H), 7.51–7.49 (m, 2H), 3.67 (s, 3H), 0.25 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 168.39, 157.91, 151.37, 139.99, 138.04, 131.78, 128.49, 127.01, 123.58, 121.85, 104.87, 95.51, 52.43, 0.01; ESI-HR-MS: (m/z) calcd. for C₁₈H₂₀NO₂Si ([M+H]⁺) 310.1258, found 310.1263.

Synthesis of methyl 2-(4-ethynylphenyl)nicotinate (13). To a stirred solution of 12 (1.00 g, 3.23 mmol) in dried THF (10 mL), cooled to 0 °C under N₂, a solution of TBAF in THF (3.23 mL, 3.23 mmol, 1.0 M in THF) was added dropwise. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, after which the mixture was poured into water (30 mL). The resulting mixture was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/3, by v/v) to give 13. Dark brown oil, 0.50 g (65%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.81 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.17 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.57 (s, 1H), 7.56–7.54 (m, 2H), 7.53–7.51 (m, 2H), 4.30 (s, 1H), 3.68 (s, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 168.35, 158.06, 151.54, 140.49, 138.19, 132.05, 128.66, 127.01, 122.62, 122.00, 83.53, 78.38, 52.56; ESI-HR-MS: (m/z) calcd. for C₁₅H₁₂NO₂ ([M+H]⁺) 238.0863, found 238.0867.

Synthesis of 2-(4-ethynylphenyl)nicotinic acid (14). To a stirred solution of 13 (0.40 g, 1.69 mmol) in MeOH (4 mL) a solution of NaOH (0.135 g, 3.38 mmol) in water (0.3 mL) was added. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction. The reaction mixture was cooled to 0 °C and concentrated HCl (0.28 mL) was added. A stirred white slurry was obtained, and the precipitate was collected via suction filtration and dried in vacuo at room temperature to give crude 14. White solid, 0.55 g. The crude product 14 was used directly in the next step without further purification or characterization.

Synthesis of (4-benzyl-4-hydroxypiperidin-1-yl)(2-(4-ethynylphenyl)pyridin-3-yl)methanone (A1). To a stirred solution of 14 (0.55 g, 2.36 mmol) in dried THF (5.5 mL), cooled to 0 °C, under N₂, EDCI (1.13 g, 5.90 mmol), HOBT (24 mg, 0.177 mmol), and DIPEA (1.83 g, 14.2 mmol) were added successively. After addition, a solution of 3·TFA (0.82 g, 2.83 mmol) in dried THF (2 mL) was added dropwise. After that, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, after which the mixture was poured into water (15 mL). The resulting mixture was extracted with EtOAc (20 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc) to give A1. White solid, 295 mg (overall 44% from 13 to A1). m.p. 155.5–156.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ: 8.73 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 7.81–7.76 (m, 1H), 7.71–7.69 (m, 1H), 7.64–7.55 (m, 3H), 7.48–7.46 (m, 1H), 7.25–7.21 (m, 2H), 7.19–7.15 (m, 2H), 7.08–7.06 (m, 1H), 4.36–4.29 (m, 3H), 4.20–4.17 (m, 0.41H), 3.02–2.96 (m, 0.71H), 2.93–2.87 (m, 1H), 2.81–2.76 (m, 1H), 2.67–2.61 (m, 1H), 2.42–2.39 (m, 0.57H), 2.27–2.24 (m, 0.56H), 1.48–1.28 (m, 2H), 1.19–1.06 (m, 1H), 0.80–0.77 (m, 0.58H), −0.08–−0.15(m, 0.56H); ¹³C NMR (151 MHz, CDCl₃) δ 167.88, 167.63, 153.91, 153.27, 150.18, 150.12, 139.39, 139.14, 136.26, 136.11, 135.75, 135.71, 132.22, 132.19, 131.45, 130.98, 130.40, 130.31, 129.37, 128.46, 128.36, 128.34, 126.86, 126.79, 123.16, 122.86, 122.62, 122.48, 83.28, 82.88, 79.21, 78.81, 69.06, 68.87, 49.13, 49.06, 42.92, 42.38, 37.63, 37.53, 36.55, 36.13, 35.62, 35.43; ESI-HR-MS: (m/z) calcd. for C₂₆H₂₅N₂O₂ ([M+H]⁺) 397.1911, found 397.1919.

Synthesis of methyl 2-(4-(dimethylphosphoryl)phenyl)nicotinate (15). Flask 1 was charged with 11 (1.00 g, 2.95 mmol), HP(=O)Me₂ (0.23 g, 2.95 mmol), and dioxane (5 mL), and the mixture thus obtained was stirred under N₂ at room temperature. Flask 2 was charged with Pd₂(dba)₃ (0.14 g, 0.148 mmol), XantPhos (0.17 g, 0.295 mmol), and dioxane (5 mL), and the mixture was stirred under N₂ at room temperature for 10 min and subsequently added to Flask 1. The mixture thus obtained was stirred, followed by addition of Et₃N (0.36 g, 3.54 mmol). Stirring was continued at room temperature overnight until TLC analysis indicated completion of the reaction. The reaction mixture was poured into water (30 mL) and extracted with EtOAc (50 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc) to give 15. White solid, 295 mg (44%). Pale yellow oil, 0.50 g (59%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.83 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.20 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.85 (dd, J = 8.3 Hz and 11.3 Hz, 2H), 7.63 (dd, J = 2.3 Hz and 8.3 Hz, 2H), 7.56 (dd, J = 4.5 Hz and 8.0 Hz, 1H), 3.70 (s, 3H), 1.71 (s, 3H), 1.68 (s, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 167.84, 157.89, 151.63, 143.49 (d, J = 3.0 Hz), 138.30, 134.76 (d, J = 98.6 Hz), 129.53 (d, J = 10.0 Hz), 128.96 (d, J = 11.9 Hz), 126.88, 122.30, 52.58, 18.11 (d, J = 71.6 Hz); ³¹P NMR (202 MHz, DMSO-d₆) δ 32.40; ESI-HR-MS: (m/z) calcd. for C₁₅H₁₇NO₃P ([M+H]⁺) 290.0941, found 290.0938.

Synthesis of 2-(4-(dimethylphosphoryl)phenyl)nicotinic acid (16). Following the procedure for the synthesis of 14 from 13, 16 was prepared from 15 (0.44 g, 1.52 mmol) and NaOH (0.12 g, 3.04 mmol) in MeOH (4.4 mL) and water (0.3 mL). Neutralization with concentrated HCl (0.25 mL) afforded crude 16 (471 mg). The crude 16 sample was used directly in the next step without further purification or characterization.

Synthesis of (4-benzyl-4-hydroxypiperidin-1-yl)(2-(4-(dimethylphosphoryl)phenyl)pyridin-3-yl)methanone (A2). Following the procedure for the synthesis of A1 from 14 and 3·TFA, A2 was prepared from 16 (0.40 g, 1.45 mmol) and 3·TFA (0.63 g, 2.18 mmol) using EDCI (0.70 g, 3.63 mmol), HOBT (15 mg, 0.109 mmol), and DIPEA (1.13 g, 8.72 mmol) in dried THF (4 mL). White foam, 0.12 g (overall 18% from 15 to A2). ¹H NMR (500 MHz, DMSO-d₆) δ 8.76–8.74 (m, 1H), 7.95–7.91 (m, 1H), 7.86–7.79 (m, 3H), 7.71–7.70 (m, 1H), 7.51–7.48 (m, 1H), 7.24–7.21 (m, 2H), 7.18–7.15 (m, 2H), 7.05–7.04 (m, 1H), 4.38–4.32 (m, 1H), 4.30–4.08 (m, 1H), 3.06–2.98 (m, 1H), 2.93–2.83 (m, 1.67H), 2.76–2.64 (m, 1H), 2.32–2.24 (m, 1H), 1.73–1.66 (m, 6H), 1.49–1.43 (m, 0.36H), 1.37–1.31 (m, 1H), 1.10–0.99 (m, 1H), 0.91–0.89 (m, 0.61H), 0.06–0.01 (m, 0.53H); ¹³C NMR (151 MHz, CDCl₃) δ 167.79, 167.65, 153.66, 153.18, 150.30, 150.24, 142.51, 142.49, 142.26, 142.24, 136.15, 136.11, 135.94, 135.91, 135.44, 135.26, 134.80, 131.60, 131.36, 130.46, 130.40, 129.89, 129.86, 129.82, 129.79, 129.58, 129.50, 128.96, 128.88, 128.46, 128.37, 126.92, 126.84, 122.92, 122.88, 69.05, 68.66, 49.09, 48.66, 43.14, 42.70, 37.77, 37.66, 36.51, 36.15, 36.07, 35.71, 18.51, 18.47, 18.16, 18.15, 18.03, 18.00, 17.69, 17.67; ³¹P NMR (203 MHz, DMSO-d₆) δ 32.39, 32.10; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₀N₂O₃P ([M+H]⁺) 449.1989, found 449.1989.

Synthesis of methyl 2-((trimethylsilyl)ethynyl)nicotinate (18). Following the procedure for the synthesis of 12 from 11, 18 was prepared from 17 (3.00 g, 13.9 mmol) and trimethylsilylacetylene (4.43 g, 45.1 mmol) using PdCl₂(PPh₃)₂ (1.47 g, 2.09 mmol), CuI (0.13 g, 0.695 mmol), and Et₃N (12 mL, 87 mmol) in dried THF (30 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 18. Black oil, 2.40 g (74%). ¹H NMR (500 MHz, CDCl₃) δ 8.71–8.70 (m, 1H), 8.22–8.20 (m, 1H), 7.34–7.31 (m, 1H), 3.96 (s, 3H), 0.30 (s, 9H). The ¹H NMR data were consistent with those reported in the literature [31].

Synthesis of methyl 2-ethynylnicotinate (19). Following the procedure for the synthesis of 13 from 12, 19 was prepared from 18 (2.40 g, 10.3 mmol) using TBAF (10.3 mL, 10.3 mmol, 1.0 M in THF) in dried THF (24 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 19. Brown oil, 1.10 g (66%). ¹H NMR (500 MHz, DMSO-d₆), δ 8.74 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.21 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.55 (dd, J = 5.0 Hz and 8.0 Hz, 1H), 4.55 (s, 1H), 3.87 (s, 3H). The ¹H NMR data were consistent with those reported in the literature [31].

Synthesis of 2-ethynylnicotinic acid (20). Following the procedure for the synthesis of 14 from 13, 20 was prepared from 19 (0.80 g, 4.96 mmol) using NaOH (0.40 g, 9.92 mmol) in MeOH (8 mL). Yellow solid, 0.72 g. This sample was used directly in the next step without further purification or characterization.

Synthesis of (4-benzyl-4-hydroxypiperidin-1-yl)(2-ethynylpyridin-3-yl)methanone (A3). Following the procedure for the synthesis of A1 from 14 and 3·TFA, A3 was prepared from 20 (0.30 g, 2.04 mmol) and 3·TFA (0.71 g, 2.45 mmol) using EDCI (0.98 g, 5.10 mmol), HOBT (21 mg, 0.109 mmol), and DIPEA (1.58 g, 12.2 mmol) in dried THF (3 mL). White solid, 0.20 g (overall 38% from 19 to A3). m.p. 138.2–139.8 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.58 (d, J = 4.5 Hz, 1H), 7.74 (s, 1H), 7.49–7.46 (m, 1H), 7.28–7.19 (m, 5H), 4.52–4.00 (m, 3H), 3.28–3.22 (m, 0.72H), 3.10–3.01 (m, 2H), 2.69 (s, 2H), 1.66–1.39 (m, 3.47H), 1.32–1.29 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 166.01, 149.97, 138.15, 136.38, 136.14, 135.91, 134.41, 133.98, 130.58, 128.29, 126.63, 123.52, 81.16, 80.34, 69.67, 69.31, 49.92, 49.29, 43.58, 42.99, 37.77, 36.86, 36.32, 36.09, 35.43; ESI-HR-MS: (m/z) calcd. for C₂₀H₂₁N₂O₂ ([M+H]⁺) 321.1598, found 321.1605.

Synthesis of (4-benzyl-4-hydroxypiperidin-1-yl)(2-chloropyridin-3-yl)methanone (21). The corresponding carboxylic acid chloride of 4 was prepared from 4 (3.0 g, 19.0 mmol) following the procedure described above using (COCl)₂ (4.82 g, 38.0 mmol) and DMF (2 drops) in dried CH₂Cl₂ (30 mL). The crude carboxylic acid chloride of 4 was dissolved in dried THF (30 mL), and the resulting mixture was cooled at 0 °C and stirred under N₂, followed by addition of 3·TFA (6.05 g, 20.9 mmol) in one portion and Et₃N (10.6 mL, 76.0 mmol) in a dropwise manner. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, after which the mixture was poured into saturated aqueous NaHCO₃ (100 mL). The mixture thus obtained was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/1, by v/v) to give 21. White solid, 1.98 g (31%). m.p. 138.4–138.9 °C. ¹H NMR (500 MHz, DMSO-d₆), δ 8.47–8.43 (m, 1H), 7.88–7.81 (m, 1H), 7.52–7.47 (m, 1H), 7.27–7.24 (m, 2H), 7.21–7.17 (m, 3H), 4.54 (d, J = 5.5 Hz, 1H), 4.26–4.22 (m, 1H), 3.30–3.21 (m, 1H), 3.13–3.02 (m, 2H), 2.71–2.70 (m, 2H), 1.58–1.40 (m, 3H), 1.36–1.29 (m, 1H). The ¹H NMR data were consistent with those reported in the literature [13].

Synthesis of 4-(3-(4-benzyl-4-hydroxypiperidine-1-carbonyl)pyridin-2-yl)benzonitrile (24). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 24 was prepared from 21 (1.00 g, 9.36 mmol) and 22 (0.53 g, 3.63 mmol) using Pd(PPh₃)₄ (0.11 g, 0.093 mmol) and Na₂CO₃ (0.96 g, 9.06 mmol) in DME/H₂O (10 mL/10 mL). Purification by column chromatography (EtOAc/PE = 1/1, by v/v) gave 24. White solid, 0.72 g (61%). m.p. 188.8–190.4 °C. ¹H NMR (500 MHz, DMSO-d₆), δ 8.77–8.75 (m, 1H), 7.97–7.93 (m, 2H), 7.86–7.75 (m, 3H), 7.54–7.51 (m, 1H), 7.25–7.15 (m, 4H), 7.06–7.05 (m, 1H), 4.41–4.39 (m, 1H), 4.29–4.15 (m, 1H), 3.09–3.03 (m, 0.73H), 2.96–2.91 (m, 1H), 2.85–2.83 (m, 1H), 2.72–2.64 (m, 1.43H), 2.44–2.32 (m, 1H), 1.51–1.31 (m, 2H), 1.13–1.05 (m, 1H), 0.93–0.90 (m, 0.58H), 0.06-0.03 (m, 0.54H); ¹³C NMR (151 MHz, CDCl₃) δ 167.38, 167.26, 152.68, 152.13, 150.28, 150.18, 143.25, 143.08, 136.03, 135.98, 135.56, 135.43, 132.14, 132.03, 131.58, 131.25, 130.41, 130.39, 130.31, 130.19, 129.77, 129.14, 128.31, 126.91, 126.82, 123.19, 123.15, 118.42, 118.26, 112.58, 68.95, 68.74, 49.26, 49.03, 42.94, 42.43, 37.53, 37.50, 36.46, 36.01, 35.74, 35.44; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₄N₃O₂ ([M+H]⁺) 398.1863, found 398.1863.

Synthesis of 4-(3-(4-benzyl-4-hydroxypiperidine-1-carbonyl)pyridin-2-yl)benzothioamide (A4). A mixture of 24 (0.50 g, 1.26 mmol), (NH₄)₂S (95 mg, 1.39 mmol), and Et₃N (0.14 g, 1.39 mmol) in pyridine (5 mL) was stirred at 50 °C under N₂ overnight until TLC analysis indicated completion of the reaction. After cooling to room temperature, the reaction mixture was poured into water (15 mL) and extracted with EtOAc (20 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/1, by v/v) to give A4. Yellow solid, 0.47 g (87%). m.p. 136.2–137.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 9.99–9.93 (m, 1H), 9.65–9.56 (m, 1H), 8.74–8.73 (m, 1H), 8.07–7.95 (m, 2H), 7.81–7.77 (m, 1H), 7.71–7.60 (m, 2H), 7.49–7.47 (m, 1H), 7.23–7.04 (m, 5H), 4.37–4.18 (m, 2H), 3.02–2.96 (m, 1H), 2.91–2.85 (m, 0.67H), 2.82–2.77 (m, 1H), 2.64 (m, 0.63H), 2.36–2.26 (m, 1H), 1.47–1.27 (m, 2H), 1.26–1.22 (m, 0.66H), 1.17–1.10 (m, 1H), 0.87–0.84 (m, 0.60H), 0.79–0.76 (m, 0.64H), −0.08–−0.14 (m, 0.67H); ¹³C NMR (151 MHz, CDCl₃) δ 201.86, 201.73, 167.98, 167.71, 153.60, 153.15, 150.33, 150.24, 141.82, 141.74, 140.30, 139.71, 136.42, 136.24, 135.83, 135.73, 131.61, 131.16, 130.59, 130.57, 129.20, 128.54, 128.45, 127.47, 127.36, 126.96, 126.88, 123.05, 122.94, 69.47, 68.97, 48.89, 48.74, 43.12, 42.74, 37.89, 37.76, 36.50, 36.08, 35.74, 35.50, 31.66, 22.73, 14.21; ESI-HR-MS: (m/z) calcd for C₂₅H₂₆N₃O₂S ([M+H]⁺) 432.1740, found 432.1741.

Synthesis of (2-(1H-benzo[d]imidazol-5-yl)pyridin-3-yl)(4-benzyl-4-hydroxypiperidin-1-yl)methanone (A5). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, A5 was prepared from 21 (0.56 g, 1.69 mmol) and 23 (0.50 g, 2.03 mmol) using Pd(PPh₃)₄ (98 mg, 0.085 mmol) and Na₂CO₃ (0.54 g, 5.07 mmol) in DME/H₂O (6 mL/6 mL). Purification by column chromatography (EtOAc) gave A5. White solid, 70 mg (10%). m.p. 137.8–138.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 12.71 (s, 1H), 8.72–8.70 (m, 1H), 8.40–8.26 (m, 1H), 7.93–7.62 (m, 4H), 7.43–7.40 (m, 1H), 7.23–7.10 (m, 4H), 6.74–6.72 (m, 1H), 4.35–4.16 (m, 2H), 2.95–2.70 (m, 3.40H), 2.64–2.54 (m, 1H), 1.93–1.90 (m, 0.60H), 1.59–1.57 (m, 0.68H), 1.44–1.19 (m, 1.68H), 1.04–0.95 (m, 1H), 0.47–0.45 (m, 0.64H), −0.72–−0.78 (m, 0.69H); ¹³C NMR (151 MHz, CD₃OD + CDCl₃) δ 168.43, 168.21, 155.31, 154.49, 149.77, 142.57, 142.21, 136.57, 136.29, 136.09, 135.65, 133.35, 133.21, 131.41, 131.02, 130.35, 130.05, 127.99, 127.81, 126.46, 126.33, 124.01, 123.22, 122.19, 122.07, 116.34, 115.86, 115.56, 114.92, 68.81, 68.40, 48.79, 43.00, 42.54, 37.66, 37.52, 36.06, 35.59, 35.44, 34.66; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₅N₄O₂ ([M+H]⁺) 413.1972, found 413.1981.

Synthesis of tert-butyl 2-(4-(dimethylcarbamoyl)phenyl)nicotinate (26). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 26 was prepared from 5 (2.00 g, 9.36 mmol) and 25 (2.16 g, 11.2 mmol) using Pd(PPh₃)₄ (0.32 g, 0.281 mmol) and Na₂CO₃ (2.98 g, 28.1 mmol) in DME/H₂O (20 mL/20 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave A5. White solid, 2.82 g (76%). m.p. 85.2–86.4 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.78 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.12 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.54–7.49 (m, 5H), 3.01 (s, 3H), 2.96 (s, 3H), 1.28 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 170.64, 166.42, 157.30, 150.43, 141.44, 137.49, 135.96, 128.52, 128.34, 126.56, 121.62, 81.94, 39.12, 34.95, 27.19; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₃N₂O₃ ([M+H]⁺) 327.1703, found 327.1702.

Synthesis of tert-butyl 2-(4-(dimethylcarbamothioyl)phenyl)nicotinate (27). A mixture of 26 (2.00 g, 6.13 mmol) and Lawesson reagent (1.49 g, 11.2 mmol) in toluene (20 mL) was refluxed overnight under N₂ until TLC analysis indicated completion of the reaction. After cooling to room temperature, the reaction mixture was poured into water (50 mL) and extracted with EtOAc (50 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc) to give 27. Pale yellow solid, 1.20 g (57%). m.p. 96.8–97.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.11 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.53–7.48 (m, 3H), 7.41–7.39 (m, 2H), 3.53 (s, 3H), 3.20 (s, 3H), 1.30 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 200.32, 166.45, 157.19, 143.35, 139.92, 138.27, 128.91, 128.56, 125.55, 122.03, 82.53, 44.05, 43.08, 27.42; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₃N₂O₂S ([M+H]⁺) 343.1475, found 343.1474.

Synthesis of 4-(3-(4-benzyl-4-hydroxypiperidine-1-carbonyl)pyridin-2-yl)-N,N-dimethylbenzothioamide (A6). To a stirred solution of 27 (2.00 g, 5.84 mmol) in CH₂Cl₂ (6 mL), cooled to 0 °C, TFA was added dropwise (10 mL). After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, after which the mixture was evaporated on a rotary evaporator to dryness. The residue thus obtained was dissolved in dried THF (20 mL), followed by addition of EDCI (2.80 g, 14.6 mmol), HOBT (59 mg, 0.438 mmol), and DIPEA (4.52 g, 35.0 mmol). The resulting mixture was stirred at 0 °C under N₂, and a solution of 3·TFA (2.03 g, 7.10 mmol) in dried THF (3 mL) was added dropwise. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, after which the mixture was poured into water (30 mL). The mixture thus obtained was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc) to give A6. Yellow solid, 1.21 g (overall 45% from 27 to A6). m.p. 89.4–91.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.73–8.72 (m, 1H), 7.81–7.76 (m, 1H), 7.70–7.58 (m, 2H), 7.49–7.35 (m, 3H), 7.25–7.18 (m, 3H), 7.17–7.11 (m, 2H), 4.31–4.09 (m, 2H), 3.60–3.51 (m, 3H), 3.21–3.13 (m, 3H), 3.06–2.96 (m, 1.43H), 2.94–2.81 (m, 2H), 2.66–2.63 (m, 1H), 2.47–2.46 (m, 0.61H), 1.47–1.29 (m, 2H), 1.12–1.00 (m, 1H), 0.94–0.91 (m, 0.52H), 0.26–0.20 (m, 0.60H). ¹³C NMR (151 MHz, CDCl₃) δ 201.60, 201.44, 167.90, 167.64, 153.50, 153.05, 150.24, 150.14, 141.56, 141.45, 140.20, 139.67, 136.40, 136.21, 135.92, 135.82, 131.44, 131.03, 130.57, 130.54, 129.03, 128.40, 128.29, 127.48, 127.41, 126.79, 126.72, 123.02, 122.92, 69.43, 68.94, 48.80, 48.68, 43.06, 42.68, 37.85, 37.73, 36.29, 35.89, 35.54, 35.36, 31.58, 22.66, 14.15; ESI-HR-MS: (m/z) calcd. for C₂₇H₃₀N₃O₂S ([M+H]⁺) 460.2053, found 460.2055.

Synthesis of (4-bromophenyl)(tert-butyl)sulfane (29). To a stirred solution of 28 (5.00 g, 26.5 mmol) and t-BuCl (3.93 g, 56 mmol) in MeCN (50 mL) at room temperature under N₂, anhydrous AlCl₃ (0.18 g, 1.33 mmol) was added in portions. After addition, the reaction mixture was stirred at room temperature until completion, as indicated by TLC analysis (typically within 2 h). The reaction mixture was slowly poured into ice–water (150 mL) and extracted with n-hexane (100 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to give a residue, which was purified by column chromatography (PE) to give 27. Pale yellow oil, 5.19 g (80%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.57 (dd, J = 1.5 Hz and 8.5 Hz, 1H), 7.41 (dd, J = 1.3 Hz and 8.3 Hz, 1H), 1.22 (s, 9H). The ¹H NMR data were consistent with those reported in the literature [32].

Synthesis of (4-(tert-butylthio)phenyl)boronic acid (30). To a stirred solution of 29 (6.48 g, 26.5 mmol) in dried THF (65 mL), cooled to −78 °C under N₂, a solution of n-BuLi in n-hexane (18.3 mL, 29.2 mmol, 1.6 M in n-hexane) was added dropwise. After addition, the reaction mixture was stirred at this temperature for an additional 1 h, followed by dropwise addition of B(OMe)₃ (5.51 g, 53.0 mmol). After addition, stirring was continued at this temperature for an additional 1 h and then at room temperature until TLC analysis indicated completion of the reaction. The reaction mixture was poured into ice–water (100 mL) and extracted with EtOAc (100 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/3, by v/v) to give 30. White solid, 4.00 g (72%). m.p. 172.3–173.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.13 (s, 2H), 7.78 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 8.0 Hz, 2H), 1.24 (s, 9H). The ¹H NMR data were consistent with those reported in the literature [33].

Synthesis of tert-butyl 2-(4-(tert-butylthio)phenyl)nicotinate (31). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 31 was prepared from 30 (0.20 g, 0.95 mmol) and 5 (0.24 g, 1.14 mmol) using Pd(PPh₃)₄ (55 mg, 0.048 mmol) and K₂CO₃ (0.39 g, 2.85 mmol) in refluxing dioxane/H₂O (2 mL/2 mL) under N₂. Purification by column chromatography (EtOAc) gave 31. White solid, 0.26 g (80%). m.p. 72.3–74.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.76 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.10 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.59 (dd, J = 2.0 Hz and 6.5 Hz, 2H), 7.53–7.49 (m, 3H), 1.29 (s, 9H), 1.26 (s, 9H); ¹³C NMR (126 MHz, CDCl₃) δ 167.14, 158.03, 150.84, 141.08, 137.93, 137.13, 133.21, 129.05, 128.90, 121.89, 82.45, 46.22, 31.02, 27.63; ESI-HR-MS: (m/z) calcd. for C₂₀H₂₆NO₂S ([M+H]⁺) 344.1679, found 344.1688.

Synthesis of (4-benzyl-4-hydroxypiperidin-1-yl)(2-(4-(tert-butylthio)phenyl)pyridin-3-yl)methanone (A7). Following the procedure for the synthesis of A6 from 27, A7 was prepared from 31. Thus, 31 (2.00 g, 5.82 mmol) was first treated with TFA (10 mL) in CH₂Cl₂ (6 mL) at room temperature to give the corresponding carboxylic acid, which was then reacted with 3·TFA (2.02 g, 6.98 mmol) using EDCI (2.80 g, 14.6 mmol), HOBT (59 mg, 0.437 mmol), and DIPEA (4.51 g, 34.9 mmol) in dried THF (20 mL). Purification by column chromatography (EtOAc) gave A7. White solid, 1.55 g (overall 58% from 31 to A7). ¹H NMR (500 MHz, DMSO-d₆) δ 8.73–8.72 (m, 1H), 7.81–7.76 (m, 1H), 7.72–7.70 (m, 1H), 7.64–7.55 (m, 3H), 7.49–7.46 (m, 1H), 7.24–7.21 (m, 2H), 7.18–7.13 (m, 2H), 7.03–7.02 (m, 1H), 4.33–4.16 (m, 2H), 3.05–2.99 (m, 0.65H), 2.95–2.87 (m, 1H), 2.81–2.71 (m, 1H), 2.62–2.55 (m, 1H), 2.37–2.23 (m, 1H), 1.46–1.36 (m, 1H), 1.33–1.26 (m, 10H), 1.23–1.16 (m, 0.41H), 1.12–1.06 (m,1H), 0.91–0.87 (m, 0.59H), 0.11–0.05 (m, 0.60H); ¹³C NMR (151 MHz, DMSO-d₆) δ 166.80, 166.73, 153.07, 152.53, 149.89, 149.84, 139.27, 139.23, 137.31, 136.94, 136.64, 135.98, 135.82, 133.30, 132.97, 131.36, 131.12, 130.51, 130.33, 129.00, 128.42, 127.54, 127.52, 125.89, 125.84, 122.71, 68.13, 67.76, 48.43, 48.31, 46.07, 45.97, 42.52, 42.10, 40.06, 37.00, 36.93, 35.89, 35.38, 35.31, 30.73; ESI-HR-MS: (m/z) calcd. for C₂₈H₃₃N₂O₂S ([M+H]⁺) 461.2257, found 461.2267.

Synthesis of tert-butyl 2-(4-aminophenyl)nicotinate (32). Following the procedure for the synthesis of 10 from 9, 32 was prepared from 8 (6.30 g, 21.0 mmol) under standard hydrogenolysis condition using 10% Pd/C (0.63 g) in MeOH (63 mL) at atmospheric pressure and room temperature. Purification by column chromatography (EtOAc/PE = 2/1, by v/v) gave 32. White solid, 4.00 g (71%). m.p. 129.4–130.7 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.64 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 7.90 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.30 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 7.24 (dd, J = 2.0 Hz and 6.5 Hz, 2H), 6.61 (dd, J = 2.0 Hz and 6.5 Hz, 2H), 5.39 (s, 2H), 1.37 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 167.77, 158.12, 150.24, 147.31, 137.31, 129.89, 129.84, 128.16, 120.38, 114.23, 81.83, 27.49; ESI-HR-MS: (m/z) calcd. for C₁₆H₁₉N₂O₂ ([M+H]⁺) 271.1441, found 271.1446.

Synthesis of tert-butyl 2-(4-isothiocyanatophenyl)nicotinate (33). To a stirred solution of 32 (1.00 g, 3.70 mmol) and Et₃N (0.75 g, 7.41 mmol) in CH₂Cl₂ (10 mL), cooled to 0 °C under N₂, CSCl₂ (0.85 g, 7.41 mmol) was added in a dropwise manner. After addition, the reaction mixture was stirred at room temperature until completion, as indicated by TLC analysis (typically within 1 h), and then poured into ice–water (15 mL). The resulting mixture was brought to pH = 7–8 with saturated aqueous NaHCO₃ and extracted with EtOAc (50 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/4, by v/v) to give 33. Pale yellow solid, 0.90 g (78%). m.p. 67.4–69.8 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.12 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.56–7.51 (m, 5H), 1.31 (s, 9H); ¹³C NMR (151 MHz, DMSO-d₆) δ 166.24, 155.99, 151.03, 139.46, 137.70, 134.18, 130.14, 130.11, 128.26, 125.57, 122.50, 81.96, 27.21; ESI-HR-MS: (m/z) calcd. for C₁₇H₁₇N₂O₂S ([M+H]⁺) 313.1005, found 313.1011.

Synthesis of tert-butyl 2-(4-(3,3-dimethylthioureido)phenyl)nicotinate (34). To a stirred solution of 33 (1.16 g, 3.71 mmol) and Et₃N (1.12 g, 11.1 mmol) in dried THF, cooled to 0 °C under N₂, Me₂NH·HCl was added in portions. After addition, the reaction mixture was stirred at room temperature until completion, as indicated by TLC analysis (typically within 1 h), and then poured into ice–water (50 mL). The resulting mixture was extracted with EtOAc (50 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 2/1, by v/v) to give 34. White solid, 1.08 g (82%). ¹H NMR (500 MHz, DMSO-d₆) δ 9.13 (s, 1H), 8.74 (d, J = 5.0 Hz, 1H), 8.04 (d, J = 7.5 Hz), 7.46–7.42 (m, 5H), 3.30 (s, 6H), 1.34 (s, 9H); ¹³C NMR (151 MHz, DMSO-d₆) δ 181.22, 167.02, 156.74, 150.71, 141.59, 137.26, 135.46, 128.43, 128.16, 124.59, 121.73, 81.90, 40.97, 27.27; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₄N₃O₂S ([M+H]⁺) 358.1584, found 358.1591.

Synthesis of 2-(4-(3,3-dimethylthioureido)phenyl)nicotinic acid hydrochloric acid salt (35). To a stirred solution of 34 (1.46 g, 4.08 mmol) in CH₂Cl₂ (4.5 mL), cooled to 0 °C, TFA (7.5 mL) was added in a dropwise manner. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, after which the mixture was evaporated on a rotary evaporator to give a residue. Another flask, cooled to 0 °C, was charged with MeOH (10 mL), to which SOCl₂ (2 mL) was added dropwise. The mixture thus obtained was stirred at this temperature for another 30 min, followed by the slow addition of the residue prepared above. The resulting mixture was stirred at room temperature for another 2 h and subsequently evaporated on a rotary evaporator to give 35 as a hydrochloric acid salt. The product was obtained as a pale yellow solid. This sample was used directly in the next step without further purification or characterization.

Synthesis of 3-(4-(3-(4-benzyl-4-hydroxypiperidine-1-carbonyl)pyridin-2-yl)phenyl)-1,1-dimethylthiourea (A8). Following the procedure for the synthesis of A1 from 14 and 3·TFA, A8 was prepared from 35 (1.60 g, 4.74 mmol) and 3·TFA (1.09 g, 5.69 mmol) using EDCI (2.28 g, 11.9 mmol), HOBT (48 mg, 0.356 mmol), and DIPEA (3.67 g, 28.4 mmol) in dried THF (16 mL). Purification by column chromatography (EtOAc) gave A8. White solid, 1.40 g (62%). m.p. 119.6–122.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 9.19–9.13 (m, 2H), 8.70–8.68 (m, 1H), 7.76–7.72 (m, 1H), 7.63–7.61 (m, 1H), 7.54–7.51 (m, 2H), 7.42–7.40 (m, 1H), 7.23–7.07 (m, 5H), 4.29–4.27 (m, 1H), 4.22–4.17 (m, 1H), 3.30–3.29 (m, 6H), 3.02–2.73 (m, 3H), 2.45–2.44 (m, 1H), 1.49–1.06 (m, 4H), 0.87–0.82 (m, 1.41H), 0.28–0.22 (m, 0.61H); ¹³C NMR (126 MHz, DMSO-d₆) δ 181.10, 181.02, 167.12, 167.07, 153.42, 153.12, 149.72, 149.66, 142.18, 141.74, 137.41, 137.34, 135.90, 135.61, 134.51, 134.18, 131.04, 130.71, 130.59, 130.55, 128.22, 127.80, 127.58, 127.37, 125.88, 125.67, 124.56, 124.08, 122.07, 122.03, 68.36, 67.95, 48.22, 48.11, 42.51, 42.22, 41.00, 37.03, 36.90, 35.97, 35.53, 35.27, 35.23, 30.96, 22.07, 13.97; ESI-HR-MS: (m/z) calcd. for C₂₇H₃₁N₄O₂S ([M+H]⁺) 475.2162, found 475.2174.

Synthesis of 3-fluoro-2,4′-bipyridine (37). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 37 was prepared from 36 (2.00 g, 11.4 mmol) and pyridine-4-boronic acid (1.54 g, 12.5 mmol) using Pd(PPh₃)₄ (0.66 g, 0.57 mmol) and K₂CO₃ (4.73 g, 34.2 mmol) in dioxane/H₂O (66 mL/33 mL). Purification by column chromatography (EtOAc/PE = 1/2, by v/v) gave 37. White solid, 1.56 g (79%). m.p. 73.3–75.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.74–8.73 (m, 2H), 8.62–8.61 (m, 1H), 7.94–7.88 (m, 3H), 7.62–7.58 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 158.31 (d, J = 263.3 Hz), 150.27, 145.90 (d, J = 5.3 Hz), 143.27 (d, J = 10.0 Hz), 142.66 (d, J = 5.4 Hz), 125.28 (d, J = 4.3 Hz), 124.70 (d, J = 20.5 Hz), 122.91 (d, J = 6.6 Hz); ¹⁹F NMR (471 MHz, CDCl₃) δ −121.62; ESI-HR-MS: (m/z) calcd. for C₁₀H₈N₂F ([M+H]⁺) 175.0667, found 175.0671.

Synthesis of [2,4′-bipyridine]-3-thiol (38). A mixture of 37 (2.00 g, 11.5 mmol), Na₂S (1.35 g, 12.76 mmol), and K₂CO₃ (3.18 g, 23.0 mmol) in DMF (50 mL) was stirred overnight at 120 °C under N₂ until TLC analysis indicated completion of the reaction. After cooling to room temperature, the reaction mixture was evaporated on a rotary evaporator to remove most of the solvent under highly reduced pressure and the residue thus obtained was diluted with water (50 mL). The resulting mixture thus obtained was extracted with EtOAc (100 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄) and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (MeOH/CH₂Cl₂ = 1/10, by v/v) to give 38. Pale yellow solid, 0.42 g (21%). m.p. 149.0–151.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.59–8.57 (m, 3H), 7.67 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.40–7.37 (m, 3H); ¹³C NMR (126 Hz, DMSO-d₆) δ 156.33, 149.38, 148.64, 146.14, 140.94, 129.81, 124.34, 123.35; ESI-HR-MS: (m/z) calcd. for C₁₀H₉N₂S ([M+H]⁺) 189.0481, found: 189.0486.

Synthesis of tert-butyl 2-([2,4′-bipyridin]-3-ylthio)-2-methylpropanoate (39). A mixture of 38 (2.70 g, 14.3 mmol), tert-butyl 2-bromo-2-methylpropanoate (4.80 g, 21.5 mmol) and K₂CO₃ (5.93 g, 12.9 mmol) in DMF (135 mL) was stirred overnight at 45 °C under N₂, when TLC analysis indicated the completion of reaction. On cooling to room temperature, the reaction mixture was evaporated on a rotary evaporator to give a residue, which was diluted with water (50 mL). The resulting mixture was extracted with EtOAc (100 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/1, by v/v) to give 39. Pale yellow oil, 1.71 g (36%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.73 (dd, J = 1.8 Hz and 4.3 Hz, 2H), 8.57 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.32 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.59 (dd, J = 1.5 Hz and 4.4 Hz, 2H), 7.56 (dd, J = 4.5 Hz and 8.0 Hz, 1H), 1.33 (s, 6H), 1.20 (s, 9H); ¹³C NMR (126 Hz, DMSO-d₆) δ 172.64, 160.26, 149.36, 149.29, 147.58, 144.97, 128.54, 125.07, 123.02, 81.63, 53.02, 27.85, 27.83, 26.17; ESI-HR-MS: (m/z) calcd. for C₁₈H₂₃N₂O₂ ([M+H]⁺) 331.1475, found 331.1482.

Synthesis of 2-([2,4′-bipyridin]-3-ylthio)-2-methylpropanoic acid hydrochloric acid salt (40). Following the procedure for the synthesis of 35 from 34, 39 (2.00 g, 6.05 mmol) was first cleaved with TFA (10 mL) in CH₂Cl₂ (10 mL), and then the corresponding carboxylic acid was converted to the hydrochloric acid salt 40 with HCl/MeOH generated by SOCl₂ (2 mL) in MeOH (10 mL). The sample was used directly in the next step without further purification or characterization.

Synthesis of 2-([2,4′-bipyridin]-3-ylthio)-1-(4-benzyl-4-hydroxypiperidin-1-yl)-2-methylpropan-1-one (B1). Following the procedure for the synthesis of 6 from 5 and 3·TFA, B1 was prepared from 40 (1.50 g, 4.83 mmol) and 3·TFA (2.79 g, 9.66 mmol) using EDCI (2.42 g, 12.6 mmol), HOBT (49 mg, 0.362 mmol), and DIPEA (2.18 g, 16.9 mmol) in dried THF (75 mL). Purification by column chromatography (EtOAc) gave B1. White solid, 1.12 g (overall 41% for 39 to B1). m.p. 71.0–73.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.67 (dd, J = 1.8 Hz and 4.3 Hz, 2H), 8.61 (dd, J = 1.5 Hz and 4.5 Hz, 1H), 7.75 (dd, J = 1.5 Hz and 3.0 Hz, 1H), 7.51 (dd, J = 1.8 Hz and 4.3 Hz, 2H), 7.40 (dd, J = 4.5 Hz and 8.0 Hz, 1H), 7.25–7.22 (m, 2H), 7.19–7.16 (m, 3H), 4.46 (s, 1H), 4.07–4.04 (m, 2H), 3.07–2.82 (m, 2H), 2.64 (m, 2H), 1.35–1.34 (m, 4H), 1.27 (s, 6H); ¹³C NMR (151 MHz, CDCl₃) δ 170.80, 158.63, 149.30, 148.50, 147.76, 141.66, 135.84, 130.57, 129.31, 128.64, 127.13, 124.81, 123.51, 69.45, 51.59, 49.36, 37.16, 28.24; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₀N₃O₂S ([M+H]⁺) 448.2053, found 448.2065.

Synthesis of 2-([2,4′-bipyridin]-3-ylsulfonyl)-1-(4-benzyl-4-hydroxypiperidin-1-yl)-2-methylpropan-1-one (B2). To a stirred solution of B1 (1.00 g, 2.23 mmol) in CH₂Cl₂ (10 mL), cooled to 0 °C, mCPBA was added portionwise (1.16 g, 6.70 mmol). After addition, the reaction temperature was slowly raised to room temperature until TLC analysis indicated completion of the reaction. The reaction mixture was poured into aqueous 10% Na₂S₂O₃ (30 mL) with ice, and the resulting mixture was extracted with EtOAc (50 mL × 3). The combined extracts were washed successively with saturated aqueous NaHCO₃ (50 mL) and brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc) to give B2. White solid, 0.88 g (82%). m.p. 139.0–141.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.93 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.31 (dd, J = 1.8 Hz and 8.3 Hz, 1H), 8.26–8.24 (m, 2H), 7.68 (dd, J = 4.5 Hz and 8.0 Hz, 2H), 7.49–7.47 (m, 2H), 7.28–7.17 (m, 5H), 4.45 (s, 1H), 3.93–3.91 (m, 2H), 3.00 (s, 2H), 2.67 (s, 2H), 1.40 (s, 6H), 1.36–1.34 (m, 4H); ¹³C NMR (151 MHz, CDCl₃) δ 165.74, 156.15, 153.49, 141.55, 137.74, 136.96, 136.26, 131.58, 130.63, 128.66, 128.36, 126.77, 122.94, 71.57, 69.06, 49.34, 42.24, 36.76, 23.59; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₀N₃O₄S ([M+H]⁺) 480.1952, found 480.1960.

Synthesis of [2,4′-bipyridin]-3-amine (42). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 42 was prepared from 41 (1.00 g, 5.78 mmol) and pyridine-4-boronic acid (0.71 g, 5.78 mmol) using Pd(PPh₃)₄ (0.33 g, 0.289 mmol) and K₂CO₃ (1.20 g, 8.67 mmol) in dioxane/H₂O (32 mL/16 mL). Purification by column chromatography (EtOAc) gave 42. White solid, 0.39 g (37%). m.p. 134–141 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.93 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.31 (dd, J = 1.8 Hz and 8.3 Hz, 1H), 8.26–8.24 (m, 2H), 7.68 (dd, J = 4.5 Hz and 8.0 Hz, 2H), 7.49–7.47 (m, 2H), 7.28–7.17 (m, 5H), 4.45 (s, 1H), 3.93–3.91 (m, 2H), 3.00 (s, 2H), 2.67 (s, 2H), 1.40 (s, 6H), 1.36–1.34 (m, 4H); ¹³C NMR (151 MHz, CDCl₃) δ 165.74, 156.15, 153.49, 141.55, 137.74, 136.96, 136.26, 131.58, 130.63, 128.66, 128.36, 126.77, 122.94, 71.57, 69.06, 49.34, 42.24, 36.76, 23.59; ESI-HR-MS: (m/z) calcd. for C₁₀H₁₀N₃ ([M+H]⁺) 172.0869, found 172.0873.

Synthesis of 3-isothiocyanato-2,4′-bipyridine (43). Following the procedure for the synthesis of 33 from 32, 43 was prepared from 42 (2.37 g, 13.8 mmol) using CSCl₂ (3.17 g, 27.6 mmol) and Et₃N (2.79 g, 27.6 mmol) in dried CH₂Cl₂ (48 mL). Crude 43, a brown solid (1.83 g), was used directly in the next step without further purification or characterization.

Synthesis of N-([2,4′-bipyridin]-3-yl)-4-benzyl-4-hydroxypiperidine-1-carbothioamide (B3). Following the procedure for the synthesis of 34 from 33 and Me₂NH·HCl, B3 was prepared from 43 (1.50 g, 7.03 mmol) and 3·TFA (2.44 g, 8.44 mmol) using Et₃N (2.14 g, 21.1 mmol) in dried THF (48 mL). Purification by column chromatography (EtOAc) gave B3. White solid, 1.85 g (65%). m.p. 190.0–192.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 9.22 (s, 1H), 8.58–8.56 (m, 3H), 7.67 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.60 (dd, J = 1.8 Hz and 4.3 Hz, 2H), 7.46 (dd, J = 4.5 Hz and 8.0 Hz, 1H), 7.30–7.27 (m, 2H), 7.24–7.22 (m, 3H), 4.55 (s, 1H), 4.40 (s, 2H), 3.37–3.30 (m, 2H), 2.71 (s, 2H), 1.41–1.38 (m, 4H); ¹³C NMR (126 MHz, DMSO-d₆) δ 180.57, 152.85, 149.37, 147.53, 146.20, 139.33, 137.44, 135.88, 130.59, 127.71, 126.02, 123.69, 123.13, 68.44, 48.57, 44.39, 36.48; ESI-HR-MS: (m/z) calcd. for C₂₃H₂₅N₄OS ([M+H]⁺) 405.1744, found 405.1754.

Synthesis of phenyl [2,4′-bipyridin]-3-ylcarbamate (44). To a stirred solution of PhOCOCl (1.50 g, 8.76 mmol) in MeCN, cooled to 0 °C under N₂, pyridine (1.23 g, 17.5 mmol) and a solution of 42 (1.00 g, 5.84 mmol) in MeCN (3 mL) were added dropwise in sequence. After addition, the reaction mixture was stirred at room temperature until TLC indicated analysis completion of the reaction (typically within 1 h) and then poured into ice–water (50 mL). The resulting mixture was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 2/1, by v/v) to give 44. White solid, 1.43 g (84%). m.p. 133.0–134.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.86–8.80 (m, 2H), 8.50–8.47 (m, 0.69H), 7.73–7.70 (m, 0.70H), 7.67–7.64 (m, 1.49H), 7.42–7.39 (m, 3H), 7.30–7.27 (m, 1.46H), 7.00–6.97 (m, 3H); ¹³C NMR (126 MHz, CDCl₃) δ 154.52, 150.54, 150.45, 150.37, 150.16, 145.38, 137.36, 132.94, 129.74, 126.73, 124.50, 123.05, 120.97; ESI-HR-MS: (m/z) calcd. for C₁₇H₁₄N₃O₂ ([M+H]⁺) 292.1081, found 292.1084.

Synthesis of N-([2,4′-bipyridin]-3-yl)-4-benzyl-4-hydroxypiperidine-1-carboxamide (B4). Following the procedure for the synthesis of B3 from 43 and 3·TFA, B4 was prepared from 44 (0.60 g, 2.06 mmol) and 3·TFA (0.79 g, 4.12 mmol) using Et₃N (0.63 g, 6.18 mmol) in dried THF (10 mL). Purification by column chromatography (EtOAc) gave B4. White solid, 0.62 g (78%). m.p. 99.0–101.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.56 (dd, J = 1.5 Hz and 4.5 Hz, 2H), 8.47 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.40 (s, 1H), 7.70 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.57 (dd, J = 1.5 Hz and 4.5 Hz, 2H), 7.41 (dd, J = 4.5 Hz and 8.0 Hz, 1H), 7.30–7.27 (m, 2H), 7.23–7.19 (m, 3H), 4.40 (s, 1H), 3.70–3.66 (m, 2H), 3.07–3.01 (m, 2H), 2.68 (m, 2H), 1.33–1.30 (m, 4H); ¹³C NMR (126 MHz, CDCl₃) δ 154.35, 150.52, 146.64, 146.02, 144.76, 135.74, 133.60, 130.57, 130.54, 128.63, 127.10, 124.12, 123.49, 69.23, 49.39, 40.47, 36.60; ESI-HR-MS: (m/z) calcd. for C₂₃H₂₅N₄O₂ ([M+H]⁺) 389.1973, found 389.1980.

Synthesis of [2,4′-bipyridine]-3-carbaldehyde (46). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 46 was prepared from 45 (10.00 g, 54.3 mmol) and pyridine-4-boronic acid (7.35 g, 59.8 mmol) using Pd(PPh₃)₄ (3.14 g, 2.72 mmol) and K₂CO₃ (22.51 g, 16.3 mmol) in dioxane/H₂O (200 mL/100 mL). Purification by column chromatography (EtOAc) gave 46. White solid, 5.20 g (57%). m.p. 108.0–110.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 10.00 (s, 1H), 8.95 (dd, J = 2.0 and 5.0 Hz, 1H), 8.75–8.74 (m, 2H), 8.34 (dd, J = 1.75 and 7.8 Hz, 1H), 7.70 (dd, J = 5.0 and 8.0 Hz, 1H), 7.66–7.65 (m, 2H). The ¹H NMR data were consistent with those reported in the literature [24].

Synthesis of (E)-[2,4′-bipyridine]-3-carbaldehyde oxime (47). To a stirred solution of 46 (5.00 g, 27.1 mmol) in EtOH/H₂O (25 mL/25 mL) at room temperature, NH₂OH·HCl (2.07 g, 29.8 mmol) and NaOH (1.08 g, 27.1 mmol) were added successively in a portionwise manner. After addition, the reaction mixture was stirred at reflux overnight until TLC analysis indicated completion of the reaction. After cooling to room temperature, the reaction mixture was poured into ice–water (50 mL) and extracted with EtOAc (50 mL × 3). The combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc) to give 47. White solid, 3.00 g (55%). m.p. 156.0–157.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 11.73 (s, 1H), 8.72–8.71 (m, 3H), 8.24 (dd, J = 2.0 Hz and 8.0 Hz, 1H), 8.01 (s, 1H), 7.54–7.52 (m, 3H); ¹³C NMR (126 MHz, CDCl₃) δ 155.05, 150.45, 149.64, 146.83, 146.34, 135.16, 127.19, 124.63, 123.75; ESI-HR-MS: (m/z) calcd. for C₁₁H₁₀N₃ O ([M+H]⁺) 200.0809, found 200.0823.

Synthesis of [2,4′-bipyridin]-3-ylmethanamine (48). To a stirred solution of 47 (0.50 g, 2.51 mmol) in EtOH/H₂O (5 mL/5 mL), cooled to 0 °C under N₂, AcONH₄ (0.48 g, 6.27 mmol) and concentrated aqueous ammonia (7.5 mL) were added successively, followed by addition of zinc powder (0.82 g, 12.6 mmol). After addition, the reaction mixture was refluxed overnight until TLC analysis indicated completion of the reaction. After cooling to room temperature, the reaction mixture was evaporated on a rotary evaporator to remove EtOH and then diluted with saturated brine (50 mL). The resulting mixture was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with saturated brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (MeOH/CH₂Cl₂ = 1/15, by v/v) to give 48. Pale yellow oil (0.24 g). This sample was directly used in the next step without further purification or characterization.

Synthesis of phenyl ([2,4′-bipyridin]-3-ylmethyl)carbamate (49). Following the procedure for the synthesis of 44 from 42, 49 was prepared from 48 (0.24 g, 1.32 mmol) and PhOCOCl (0.31 g, 1.98 mmol) using pyridine (0.52 g, 6.64 mmol) in MeCN (5 mL). Purification by column chromatography (EtOAc) gave 49. Colorless oil, 0.05 g. This sample was directly used in the next step without characterization.

Synthesis of N-([2,4′-bipyridin]-3-ylmethyl)-4-benzyl-4-hydroxypiperidine-1-carboxamide (B5). Following the procedure for the synthesis of B3 from 43 and 3·TFA, B5 was prepared from 49 (0.10 g, 0.328 mmol) and 3·TFA (0.19 g, 0.656 mmol) using Et₃N (0.10 g, 0.984 mmol) in dried THF (10 mL). Purification by column chromatography (EtOAc) gave B5. White solid, 50 mg (overall 76% for 47 to B5). m.p. 181.3–183.4 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.67 (d, J = 5.0 Hz, 2H), 8.55 (d, J = 4.5 Hz, 1H), 7.76 (d, J = 8.0 Hz, 1H), 7.57 (d, J = 5.0 Hz, 2H), 7.43 (dd, J = 4.5 Hz and 8.0 Hz, 1H), 7.27–7.24 (m, 2H), 7.21–7.18 (m, 3H), 7.01 (t, J = 5.5 Hz, 1H), 4.35 (s, 1H), 4.24–4.23 (m, 2H), 3.63–3.59 (m, 2H), 3.03–2.97 (m, 2H), 2.67 (s, 2H), 1.36–1.28 (m, 4H); ¹³C NMR (126 MHz, CDCl₃) δ 157.31, 155.39, 150.01, 148.48, 147.68, 137.15, 135.91, 133.35, 130.61, 128.59, 127.03, 123.77, 123.60, 69.35, 49.40, 41.95, 40.22, 36.55; ESI-HR-MS: (m/z) calcd. for C₂₄H₂₇N₄O₂ ([M+H]⁺) 403.2199, found 403.2139.

Synthesis of (2-bromopyridin-3-yl)methanol (50). To a stirred solution of 45 (3.00 g, 16.1 mmol) in MeOH (30 mL), cooled to 0 °C under N₂, NaBH₄ (0.73 g, 19.3 mmol) was added portionwise. After addition, the reaction temperature was slowly raised to room temperature until TLC analysis indicated completion of the reaction. The reaction mixture was poured into saturated aqueous NH₄Cl (100 mL), and the resulting mixture was extracted with EtOAc (100 mL × 3). The combined extracts were washed with saturated brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/3, by v/v) to give 50. White solid, 2.90 g (96%). m.p. 66.0–69.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.28–8.26 (m, 1H), 7.90–7.88 (m, 1H), 7.49–7.46 (m, 1H), 5.60 (s, 1H), 4.49 (s, 2H). The ¹H NMR data were consistent with those reported in the literature [34].

Synthesis of 2-bromo-3-(bromomethyl)pyridine (51). To a stirred solution of 50 (2.82 g, 15.0 mmol) in dried CH₂Cl₂ (30 mL), cooled to 0 °C under N₂, PBr₃ (8.12 g, 30.0 mmol) was added in a dropwise manner. After addition, the reaction mixture was stirred at reflux until completion, as indicated by TLC analysis (typically within 3 h). After cooling to room temperature, the reaction mixture was slowly poured into saturated aqueous NaHCO₃ (100 mL), and the resulting mixture was extracted with EtOAc (100 mL × 3). The combined extracts were washed with saturated brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/5, by v/v) to give 51. Pale yellow oil, 1.90 g (51%). ¹H NMR (500 MHz, CD₃OD) δ 8.28 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 7.95 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.41 (dd, J = 5.0 Hz and 7.5 Hz, 1H), 4.65 (s, 2H). The ¹H NMR data were consistent with those reported in the literature [35].

Synthesis of 2-(2-bromopyridin-3-yl)acetonitrile (52). To a stirred solution of 51 (3.40 g, 13.6 mmol) in MeCN (34 mL), cooled to 0 °C under N₂, TMSCN (4.05 g, 40.8 mmol) was added slowly, followed by dropwise addition of a solution of TBAF in THF (17.7 mL, 17.7 mmol, 1.0 M in THF). After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction and was then poured into ice–water (100 mL). The resulting mixture was extracted with EtOAc (100 mL × 3), and the combined extracts were washed with saturated brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/4, by v/v) to give 52. White solid, 2.30 g (85%). m.p. 80.0–82.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.39 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 7.96 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.53 (dd, J = 4.5 Hz and 7.5 Hz, 1H), 4.11 (s, 2H). The ¹H NMR data were consistent with those reported in the literature [36].

Synthesis of 2-([2,4′-bipyridin]-3-yl)acetonitrile (53). Following the procedure for the synthesis of 6 from 5 and pyridine-4-boronic acid, 53 was prepared from 52 (1.85 g, 9.39 mmol) and pyridine-4-boronic acid (1.39 g, 11.3 mmol) using Pd (PPh₃)₄ (0.34 g, 0.282 mmol) and Na₂CO₃ (2.99 g, 28.2 mmol) in DME/H₂O (20 mL/20 mL). White solid, 1.02 g (56%). m.p. 150.0–152.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.72 (dd, J = 3.5 Hz and 4.3 Hz, 2H), 8.69 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.01 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.57–7.54 (m, 3H), 4.14 (s, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 155.93, 150.44, 149.75, 146.36, 137.73, 124.21, 123.96, 123.39, 116.94, 21.77; ESI-HR-MS: (m/z) calcd. for C₁₂H₁₀N₃ ([M+H]⁺) 196.0870, found 196.0870.

Synthesis of methyl 2-([2,4′-bipyridin]-3-yl)acetate (54). To a stirred solution of 53 (1.00 g, 5.12 mmol) in AcOH (20 mL)/H₂O (2 mL), cooled to 0 °C under N₂, concentrated H₂SO₄ (2 mL) was added dropwise. After addition, the reaction mixture was refluxed overnight until TLC analysis indicated completion of the reaction. Upon cooling to room temperature, the reaction mixture was evaporated on a rotary evaporator to afford a residue, which was diluted with a mixed solvent of MeOH (4 mL) and CH₂Cl₂ (40 mL). The mixture thus obtained was dried (MgSO₄) and evaporated on a rotary evaporator to afford a residue, which was dissolved in MeOH (10 mL). The resulting solution was cooled at 0 °C, followed by dropwise addition of SOCl₂ (2 mL), and the reaction mixture was then refluxed under N₂ overnight, until TLC analysis indicated completion of the reaction. Upon cooling to room temperature, saturated aqueous NaHCO₃ was slowly added to the reaction mixture until pH > 8. The mixture thus obtained was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with saturated brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/1, by v/v) to give 54. Pale yellow oil, 0.55 g (47%). ¹H NMR (500 MHz, CDCl₃) δ 8.73–8.72 (m, 2H), 8.64 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 7.76 (dd, J = 1.8 Hz and 7.8 Hz, 1H), 7.44 (d, J = 6.0 Hz, 2H), 7.35 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 3.68 (s, 3H), 3.70 (s, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 171.20, 156.53, 149.91, 148.70, 147.53, 139.13, 127.78, 123.79, 123.40, 52.39, 37.90; ESI-HR-MS: (m/z) calcd. for C₁₃H₁₃N₂O₂ ([M+H]⁺) 229.0972, found 229.0971.

Synthesis of methyl 2-([2,4′-bipyridin]-3-yl)-2-methylpropanoate (55). To a stirred solution of 54 (0.50 g, 2.19 mmol) in dried THF (5 mL), cooled to −78 °C under N₂, a solution of LiHMDS in THF (6.6 mL, 6.6 mmol, 1.0 M in THF) was added dropwise. After addition, the resulting mixture was stirred at this temperature for another 1 h, followed by dropwise addition of a solution of MeI (0.93 g, 6.57 mmol) in dried THF (5 mL). After addition, the reaction mixture was stirred at this temperature for 1 h and then at room temperature overnight until LC-MS analysis indicated completion of the reaction and was then poured into ice–water (20 mL). The mixture thus obtained was extracted with EtOAc (30 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/1, by v/v) to give 55. White solid, 0.47 g (84%). m.p 103.1–105.3 °C. ¹H NMR (500 MHz, CDCl₃) δ 8.68 (d, J = 5.0 Hz, 2H), 8.57 (dd, J = 1.3 Hz and 4.8 Hz, 1H), 7.88 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.38 (dd, J = 4.8 Hz and 8.3 Hz, 1H), 7.27–7.26 (m, 2H), 3.37 (s, 3H), 1.53 (s, 6H); ¹³C NMR (126 MHz, CDCl₃) δ 176.49, 156.26, 149.42, 149.30, 147.32, 138.62, 134.84, 124.17, 123.18, 52.13, 45.84, 28.28; ESI-HR-MS: (m/z) calcd. for C₁₅H₁₇N₂O₂ ([M+H]⁺) 257.1285, found 257.1285.

Synthesis of 2-([2,4′-bipyridin]-3-yl)-2-methylpropanoic acid (56). To a stirred solution of 55 (0.43 g, 1.68 mmol) in MeOH (5 mL) a solution of NaOH (0.13 g, 3.36 mmol) in H₂O (1 mL) was added. After addition, the reaction mixture was stirred at 45 °C overnight until TLC analysis indicated completion of the reaction. Upon cooling to room temperature, the reaction mixture was cooled in an ice–water bath, followed by dropwise addition of concentrated HCl (0.28 mL, 3.36 mmol). After that, the mixture became a white slurry, and stirring was continued for another 1 h. The precipitate was collected via suction filtration and dried in vacuo at room temperature to give 56. White solid, 0.12 g (34%). m.p. 135.4–137.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 12.44 (s, 1H), 8.59–8.58 (m, 2H), 8.51–8.49 (m, 1H), 7.99–7.97 (m, 1H), 7.47 (dd, J = 4.8 Hz and 8.3 Hz, 1H), 7.27–7.26 (m, 2H), 1.36 (s, 6H); ¹³C NMR (151 MHz, CD₃OD) δ 179.88, 157.11, 151.31, 149.57, 147.52, 140.69, 137.16, 126.45, 125.01, 46.69, 28.17; ESI-HR-MS: (m/z) calcd. for C₁₄H₁₅N₂O₂ ([M+H]⁺) 243.1129, found 243.1129.

Synthesis of 2-([2,4′-bipyridin]-3-yl)-1-(4-benzyl-4-hydroxypiperidin-1-yl)-2-methylpropan-1-one (B6). Following the procedure for the synthesis of 21 from 4 and 3·TFA, 56 (0.60 g, 2.48 mmol) was first treated with (COCl)₂ (0.94 g, 7.44 mmol) using DMF (one drop) as catalyst in dried CH₂Cl₂ (6 mL) to give the corresponding carboxylic acid chloride, which was subsequently treated with 3·TFA (0.93 g, 3.22 mmol) using Et₃N (1.51 g, 14.9 mmol) in dried THF (8 mL) to give B6 after column chromatography (EtOAc/PE = 1/1, by v/v). White solid, 0.13 g (16%). m.p 150.3–152.4 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.53–8.51 (m, 3H), 7.91 (dd, J = 1.8 Hz and 8.3 Hz, 1H), 7.45 (dd, J = 4.8 Hz and 8.3 Hz, 1H), 7.25–7.13 (m, 7H), 4.34 (s, 1H), 3.61–3.58 (m, 1H), 2.90–2.87 (m, 1H), 2.73–2.69 (m, 1H), 2.60 (s, 2H), 2.48–2.36 (m, 1H), 1.41 (s, 3H), 1.37 (s, 3H), 1.27–1.12 (m, 4H); ¹³C NMR (126 MHz, CDCl₃) δ 172.37, 154.92, 148.95, 148.81, 147.36, 139.92, 135.90, 134.56, 130.53, 128.54, 126.97, 123.78, 123.64, 69.23, 49.43, 45.98, 42.27, 37.99, 36.71, 36.25, 31.52, 28.52; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₀N₃O₂ ([M+H]⁺) 416.2333, found: 416.2332.

Synthesis of methyl 1-([2,4′-bipyridin]-3-yl)cyclopropane-1-carboxylate (57). To a stirred solution of 54 (3.00 g, 13.1 mmol) in dried THF (30 mL), cooled to −78 °C under N₂, a solution of LiHMDS in THF (15.7 mL, 15.7 mmol, 1.0 M in THF) was added dropwise. After addition, the resulting mixture was stirred at this temperature for another 1 h, followed by dropwise addition of a solution of 1,3,2-dioxathiolane 2,2-dioxide (1.95 g, 15.7 mmol) in dried THF (6 mL). After addition, the resulting mixture was stirred at −20 °C for 1.5 h and then cooled to −78 °C, followed by addition of a solution of LiHMDS in THF (15.7 mL, 15.7 mmol, 1.0 M in THF). After that, the reaction mixture was stirred at room temperature overnight until LC-MS analysis indicated completion of the reaction, and poured into ice–water (100 mL). The mixture thus obtained was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/1, by v/v). White solid, 2.00 g (60%). m.p. 89.1–91.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.66 (dd, J = 1.5 Hz and 4.5 Hz, 2H), 8.61 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 7.91 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.46 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 7.40 (dd, J = 1.8 Hz and 4.3 Hz, 1H), 3.52 (s, 3H), 1.39 (d, J = 3.5 Hz, 2H), 1.08 (d, J = 3.0 Hz, 2H); ¹³C NMR (126 MHz, CD₃OD) δ 177.23, 157.41, 152.88, 149.20, 147.94, 142.91, 136.27, 126.37, 125.46, 28.26, 19.41; ESI-HR-MS: (m/z) calcd. for C₁₅H₁₅N₂O₂ ([M+H]⁺) 255.1129, found 255.1127.

Synthesis of 1-([2,4′-bipyridin]-3-yl)cyclopropane-1-carboxylic acid (58). Following the procedure for the synthesis of 56 from 55, 58 was prepared from 57 (2.00 g, 7.87 mmol) first by treatment with NaOH (0.94 g, 23.6 mmol) in a mixture of MeOH (20 mL)/H₂O (2 mL), and subsequent acidification with concentrated HCl (1.97 mL, 23.6 mmol). White solid, 1.43 g (76%). ¹H NMR (500 MHz, DMSO-d₆) δ 12.69 (s, 1H), 8.77 (d, J = 5.5 Hz, 2H), 8.63 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 7.94 (dd, J = 1.5 Hz and 7.5 Hz, 1H), 7.65 (d, J = 5.0 Hz, 2H), 7.49 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 1.39 (s, 2H), 0.97 (s, 2H); ¹³C NMR (126 MHz, CD₃OD) δ 177.18, 157.42, 152.90, 149.21, 147.94, 142.89, 136.28, 126.38, 125.44, 28.26, 19.40; ESI-HR-MS: (m/z) calcd. for C₁₄H₁₃N₂O₂ ([M+H]⁺) 241.0972, found 241.0971.

Synthesis of (1-([2,4′-bipyridin]-3-yl)cyclopropyl)(4-benzyl-4-hydroxypiperidin-1-yl)methanone (B7). Following the procedure for the synthesis of B6 from 56, 58 (0.50 g, 2.08 mmol) was first treated with (COCl)₂ (0.53 g, 4.16 mmol) in the presence of DMF (one drop) in dried CH₂Cl₂ (5 mL) to form the corresponding carboxylic acid chloride, which was subsequently treated with 3·TFA (0.78 g, 2.70 mmol) in the presence of Et₃N (1.26 g, 12.5 mmol) in dried THF (5 mL) to give B7 after column chromatography (EtOAc). White solid, 0.33 g (38%). m.p. 122.5–124.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.56 (dd, J = 1.3 Hz and 4.8 Hz, 1H), 8.46 (dd, J = 1.5 Hz and 4.5 Hz, 2H), 7.87 (dd, J = 1.5 Hz and 8.0 Hz, 1H), 7.43 (dd, J = 4.5 Hz and 8.0 Hz, 1H), 7.31–7.28 (m, 2H), 7.24–7.21 (m, 1H), 7.17–7.16 (m, 2H), 7.08–7.07 (m, 2H), 4.31 (s, 1H), 3.26–3.22 (m, 2H), 2.64–2.55 (m, 4H), 1.43–1.33 (m, 4H), 1.00–0.82 (m, 4H); ¹³C NMR (126 MHz, CDCl₃) δ 169.52, 157.14, 149.35, 147.81, 147.28, 135.98, 135.14, 134.17, 130.54, 128.55, 127.05, 124.12, 123.44, 69.49, 49.57, 35.76, 27.85, 16.19; ESI-HR-MS: (m/z) calcd. for C₂₆H₂₈N₃O₂ ([M+H]⁺) 414.2177, found 414.2174.

Synthesis of tert-butyl 4-benzyl-4-cyanopiperidine-1-carboxylate (68). To a stirred solution of 67 (3.00 g, 14.3 mmol) in dried THF (30 mL), cooled to −78 °C under N₂, a solution of LDA in THF (9.3 mL, 18.6 mmol, 2.0 M in THF) was added dropwise. After addition, the mixture thus obtained was stirred at this temperature for 40 min, followed by dropwise addition of BnBr (3.18 g, 18.6 mmol). After that, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, and poured into ice–water (50 mL). The resulting mixture was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/10, by v/v) to give 68. White solid, 3.50 g (82%). m.p. 85.1–86.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.36–7.33 (m, 2H), 7.30–7.27 (m, 3H), 4.00–3.97 (m, 2H), 2.91–2.78 (m, 4H), 1.76–1.73 (m, 2H), 1.57–1.51 (m, 2H), 1.40 (s, 9H); ¹³C NMR (126 MHz, CDCl₃) δ 154.54, 134.42, 130.39, 128.62, 127.68, 121.95, 80.15, 45.95, 40.93, 39.24, 34.77, 28.50; ESI-HR-MS: (m/z) calcd. for C₁₈H₂₄N₂NaO₂ ([M+Na]⁺) 323.1730, found 323.1737.

Synthesis of tert-butyl 4-benzyl-4-carbamoylpiperidine-1-carboxylate (69). To a stirred solution of 68 (2.00 g, 6.66 mmol) in DMSO (20 mL), cooled to 0 °C, K₂CO₃ (1.82 g, 13.2 mmol) and H₂O₂ (1.13 g, 33.3 mmol) were added successively. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, and poured into ice–water (60 mL). The resulting mixture was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc/PE = 1/5, by v/v) to give 69. White solid, 2.00 g (94%). m.p. 159.9–162.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.29–7.23 (m, 3H), 7.21–7.18 (m, 1H), 7.14–7.12 (m, 2H), 7.05 (br, 1H), 3.71–3.68 (m, 2H), 2.84–2.77 (m, 4H), 1.91–1.89 (m, 2H), 1.37 (s, 9H), 1.30–1.24 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 177.05, 154.96, 136.32, 130.30, 128.29, 126.98, 79.75, 46.79, 46.24, 41.46, 41.03, 40.70, 33.55, 28.53; ESI-HR-MS: (m/z) calcd. for C₁₈H₂₇N₂O₃ ([M+H]⁺) 319.2017, found 319.2017.

Synthesis of tert-butyl 4-amino-4-benzylpiperidine-1-carboxylate (70). To a stirred solution of 69 (1.93 g, 6.06 mmol) in MeCN/H₂O (10 mL/10 mL) at room temperature, PIFA (2.61 g, 6.06 mmol) was added. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, and poured into ice–water (50 mL). The resulting mixture was extracted with EtOAc (50 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (EtOAc) to give 70. White solid, 0.96 g (55%). m.p. 163.4–166.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.83 (br, 2H), 7.38–7.31 (m, 3H), 7.25–7.24 (m, 2H), 3.50–3.46 (m, 4H), 2.98–2.97 (m, 2H), 1.64–1.58 (m, 4H), 1.38 (s, 9H); ¹³C NMR (126 MHz, CDCl₃) δ 154.90, 137.50, 130.39, 128.02, 126.17, 79.30, 45.84, 40.98, 39.80, 39.12, 36.46, 31.99, 28.37; ESI-HR-MS: (m/z) calcd. for C₁₇H₂₇N₂O₂ ([M+H]⁺) 291.2067, found 291.2065.

General Procedure 1: Synthesis of 71-1, 72-1, 72-3, and 72-4. To a stirred solution of 70 (1.0 eq) in dried CH₂Cl₂ (10 v/w, based on 70), cooled to 0 °C under N₂, Et₃N (2–3 eq) was added, followed by dropwise addition of carbonyl or sulfonyl chloride (1.2–1.5 eq). After that, the reaction mixture was stirred at room temperature until completion, as indicated by TLC analysis (typically within 2–3 h), and poured into ice–water. The resulting mixture thus obtained was extracted with CH₂Cl₂ in three portions, and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography to give the desired product.

General Procedure 2: Synthesis of 71-2, 71-3, 72-2, and 72-5 to 72-8. To a stirred solution of 70 (1.0 eq) and DMAP (0.2 eq) in dried CH₂Cl₂ (10 v/w, based on 70), cooled to 0 °C under N₂, Et₃N (2–3 eq) was added, followed by dropwise addition of carbonyl or sulfonyl anhydride (1.2–1.5 eq). after that, the reaction mixture was stirred at room temperature until completion, as indicated by TLC analysis (typically within 2–3 h), and poured into ice–water. The resulting mixture thus obtained was extracted with CH₂Cl₂ in three portions, and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography to give the desired product.

tert-butyl 4-benzyl-4-(methylsulfonamido)piperidine-1-carboxylate (71-1). Compound 71-1 was prepared according to General Procedure 2 from 70 (2.00 g, 6.89 mmol) using Ms₂O (1.44 g, 8.27 mmol), DMAP (0.17 g, 1.38 mmol), and Et₃N (1.41 g, 13.8 mmol) in dried CH₂Cl₂ (20 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 71-1. White foam. 1.20 g (47%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.31–7.27 (m, 4H), 7.23–7.20 (m, 1H), 6.74 (s, 1H), 3.62 (d, J = 13.5 Hz, 2H), 3.12 (br, 2H), 3.01 (s, 5H), 1.81 (d, J = 13.5 Hz, 2H), 1.45–1.39 (m, 2H), 1.36 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 154.63, 135.80, 131.19, 128.17, 126.77, 79.78, 58.53, 45.66, 45.04, 39.91, 39.17, 34.40, 28.38; ESI-HR-MS: (m/z) calcd. for C₁₈H₂₈NaN₂O₄S ([M+Na]⁺) 391.1662, found 391.1664.

tert-butyl 4-benzyl-4-((trifluoromethyl)sulfonamido)piperidine-1-carboxylate (71-2). Compound 71-2 was prepared according to General Procedure 2 from 70 (1.50 g, 5.17 mmol) using Tf₂O (1.75 g, 6.20 mmol), DMAP (0.13 g, 1.03 mmol), and Et₃N (1.04 g, 10.3 mmol) in dried CH₂Cl₂ (15 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 71-2. White foam, 1.10 g (50%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.37 (s, 1H), 7.31–7.22 (m, 5H), 3.66–3.62 (m, 2H), 2.98–2.92 (m, 4H), 1.90–1.87 (m, 1H), 1.68–1.65 (m, 1H), 1.60–1.54 (m, 1H), 1.48–1.42 (m, 1H), 1.34 (s, 9H); ¹⁹F NMR (471 MHz, DMSO-d₆) δ −76.26; ¹³C NMR (151 MHz, CDCl₃) δ 154.63, 134.38, 128.60, 127.31, 123.81 (q, J = 332.6 Hz), 79.96, 57.55, 49.67, 39.40, 38.59, 35.61, 33.93, 28.44; ESI-HR-MS: (m/z) calcd. for C₁₈H₂₄F₃N₂O₄S ([M-H]⁻) 421.1414, found 421.1416.

tert-butyl 4-benzyl-4-(ethylsulfonamido)piperidine-1-carboxylate (71-3). Compound 71-3 was prepared according to General Procedure 1 from 70 (1.50 g, 5.17 mmol) using CH₃CH₂SO₂Cl (0.80 g, 6.20 mmol) and Et₃N (1.04 g, 10.3 mmol) in dried CH₂Cl₂ (15 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 71-3. White foam, 0.11 g (6%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.32–7.27 (m, 4H), 7.23–7.20 (m, 1H), 6.67 (s, 1H), 3.62–3.58 (m, 2H), 3.08–3.00 (m, 2H), 1.82–1.79 (m, 2H), 1.45–1.39 (m, 2H), 1.36 (s, 9H), 1.22 (t, J = 7.3 Hz, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 154.60, 135.79, 131.22, 128.18, 126.78, 79.78, 58.43, 50.98, 45.70, 39.94, 30.24, 34.46, 28.38, 8.52; ESI-HR-MS: (m/z) calcd. for C₁₉H₃₀N₂NaO₄S ([M+Na]⁺) 405.1818, found 405.1815.

tert-butyl 4-acetamido-4-benzylpiperidine-1-carboxylate (72-1). Compound 72-1 was prepared according to General Procedure 1 from 70 (0.30 g, 1.03 mmol) using AcCl (97 mg, 1.24 mmol) and Et₃N (0.21 g, 2.06 mmol) in dried CH₂Cl₂ (3 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-1. White foam, 0.18 g (52%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.30–7.27 (m, 2H), 7.22–7.19 (m, 1H), 7.17 (s, 1H), 7.09–7.07 (m, 2H), 3.69–3.66 (m, 2H), 2.96 (s, 2H), 2.85 (s, 2H), 2.00–1.96 (m, 2H), 1.83 (s, 3H), 1.38 (s, 9H), 1.36–1.32 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 170.68, 154.78, 136.82, 130.47, 127.98, 126.43, 79.58, 54.86, 43.18, 39.93, 38.96, 34.09, 28.39, 24.25; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₈N₂NaO₃ ([M+Na]⁺) 355.1992, found 355.1990.

tert-butyl 4-benzyl-4-propionamidopiperidine-1-carboxylate (72-2). Compound 72-2 was prepared according to General Procedure 2 from 70 (1.50 g, 5.17 mmol) using (CH₃CH₂CO)₂O (0.81 g, 6.20 mmol), DMAP (0.13 g, 1.03 mmol), and Et₃N (1.04 g, 10.3 mmol) in dried CH₂Cl₂ (15 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-2. White foam, 1.28 g (72%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.29–7.26 (m, 2H), 7.22–7.18 (m, 1H), 7.08–7.06 (m, 2H), 3.70–3.67 (m, 2H), 2.96 (s, 2H), 2.84 (s, 2H), 2.10–2.06 (m, 2H), 2.02-1.99 (m, 2H), 1.38 (s, 9H), 1.02 (t, J = 7.5 Hz, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 174.18, 154.54, 136.63, 130.32, 127.71, 126.20, 79.29, 54.33, 43.13, 39.76, 38.77, 33.88, 30.22, 28.19, 9.95; ESI-HR-MS: (m/z) calcd. for C₂₀H₃₀N₂NaO₃ ([M+Na]⁺) 369.2149, found 369.2146.

tert-butyl 4-benzyl-4-(cyclopropanecarboxamido)piperidine-1-carboxylate (72-3). Compound 72-3 was prepared according to General Procedure 1 from 70 (0.30 g, 1.03 mmol) using cyclopropanecarbonyl chloride (0.65 g, 6.20 mmol) and Et₃N (1.04 g, 10.3 mmol) in dried CH₂Cl₂ (15 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-3. White foam, 0.65 g (35%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.40 (s, 1H), 7.29–7.26 (m, 2H), 7.22–7.19 (m, 2H), 7.08–7.06 (m, 2H), 3.70–3.68 (m, 2H), 2.96 (s, 2H), 2.87 (s, 2H), 2.01–1.99 (m, 2H), 1.65–1.60 (m, 1H), 1.38 (s, 9H), 1.36–1.35 (m, 2H), 0.73–0.70 (m, 2H), 0.63–0.59 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 173.78, 154.91, 136.85, 130.68, 128.02, 126.49, 79.65, 54.87, 43.46, 39.94, 39.01, 34.41, 28.46, 15.38, 6.87; ESI-HR-MS: (m/z) calcd. for C₂₁H₃₁N₂O₃ ([M+H]⁺) 359.2329, found 1359.2325.

tert-butyl 4-benzyl-4-pivalamidopiperidine-1-carboxylate (72-4). Compound 72-4 was prepared according to General Procedure 1 from 70 (0.20 g, 0.689 mmol) using pivaloyl chloride (0.12 g, 1.03 mmol) and Et₃N (0.21 g, 2.07 mmol) in dried CH₂Cl₂ (2 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-4. White solid, 0.20 g (78%). m.p. 91.3–93.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.27–7.24 (m, 2H), 7.21–7.17 (m, 1H), 7.07–7.05 (m, 2H), 6.22 (s, 1H), 3.71–3.68 (m, 2H), 2.95 (s, 2H), 2.79 (s, 2H), 2.14–2.11 (m, 1H), 1.38 (s, 9H), 1.35–1.29 (m, 2H), 1.09 (s, 9H); ¹³C NMR (126 MHz, CDCl₃) δ 178.37, 154.89, 136.78, 130.77, 127.99, 126.60, 79.81, 54.19, 43.50, 39.56, 34.34, 28.52, 27.87, 27.19; ESI-HR-MS: (m/z) calcd. for C₂₂H₃₅N₂O₃ ([M+H]⁺) 375.2643, found 375.2650.

tert-butyl 4-benzyl-4-(2,2,2-trifluoroacetamido)piperidine-1-carboxylate (72-5). Compound 72-5 was prepared according to General Procedure 2 from 70 (0.30 g, 1.03 mmol) using (CF₃CO)₂O (0.26 g, 1.24 mmol), DMAP (25 mg, 0.206 mmol), and Et₃N (0.21 g, 2.06 mmol) in dried CH₂Cl₂ (3 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-5. White foam, 0.24 g (60%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.57 (s, 1H), 7.32–7.28 (m, 2H), 7.25–7.22 (m, 1H), 7.08–7.06 (m, 2H), 3.74–3.71 (m, 2H), 2.99 (s, 2H), 2.82 (s, 2H), 2.14–2.11 (m, 2H), 1.53–1.47 (m, 2H), 1.39 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 156.94 (q, J = 36.3 Hz), 154.69, 135.40, 130.43, 128.45, 127.13, 115.53 (q, J = 289.6 Hz), 80.02, 56.49, 42.96, 39.78, 38.90, 33.81, 28.44; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −73.69; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₄F₃N₂O₃ ([M-H]⁻) 385.1745, found 385.1743.

tert-butyl 4-benzyl-4-(2,2-difluoroacetamido)piperidine-1-carboxylate (72-6). Compound 72-6 was prepared according to General Procedure 2 from 70 (0.10 g, 0.344 mmol) using (CHF₂CO)₂O (90 mg, 0.516 mmol), DMAP (8 mg, 0.069 mmol), and Et₃N (0.10 g, 1.03 mmol) in dried CH₂Cl₂ (1 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-6. White solid, 0.10 g (80%). m.p. 87.9–90.4 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.09 (s, 1H), 7.30–7.27 (m, 2H), 7.24–7.21 (m, 1H), 7.09–7.07 (m, 2H), 6.10 (t, J = 54.0 Hz, 1H), 3.73–3.70 (m, 2H), 2.99 (s, 2H), 2.83 (s, 2H), 2.05–2.02 (m, 2H), 1.51–1.43 (m, 2H), 1.38 (s, 9H); ¹³C NMR (126 MHz, CDCl₃) δ 162.57 (t, J = 24.1 Hz), 154.74, 135.73, 130.49, 128.31, 126.94, 108.52 (t, J = 254.1 Hz), 79.91, 55.70, 43.22, 39.70, 38.96, 33.88, 28.44; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −124.41; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₆N₂F₂NaO₃ ([M+Na]⁺) 391.1804, found 391.1804.

tert-butyl 4-benzyl-4-((methoxycarbonyl)amino)piperidine-1-carboxylate (72-7). Compound 72-7 was prepared according to General Procedure 2 from 70 (0.50 g, 1.72 mmol) using (CH₃OCO)₂O (0.28 g, 2.06 mmol), DMAP (42 mg, 0.342 mmol), and Et₃N (0.35 g, 3.42 mmol) in dried CH₂Cl₂ (5 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-7. White foam, 0.46 g (77%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.29–7.26 (m, 2H), 7.22–7.19 (m, 1H), 7.07 (d, J = 7.5 Hz, 2H), 6.77 (s, 1H), 3.67–3.65 (m, 2H), 3.56 (s, 3H), 2.91 (br, 4H), 1.94–1.91 (m, 2H), 1.38 (s, 9H), 1.36–1.30 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 155.62, 154.74, 136.55, 130.46, 128.02, 126.46, 79.46, 53.69, 51.70, 44.09, 39.77, 38.90, 34.23, 28.38; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₈N₂NaO₄ ([M+Na]⁺) 371.1941, found 371.1939.

tert-butyl 4-benzyl-4-((ethoxycarbonyl)amino)piperidine-1-carboxylate (72-8). Compound 72-8 was prepared according to General Procedure 2 from 70 (0.50 g, 1.72 mmol) using (CH₃CH₂OCO)₂O (0.33 g, 2.06 mmol), DMAP (42 mg, 0.342 mmol), and Et₃N (0.35 g, 3.42 mmol) in dried CH₂Cl₂ (5 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 72-8. White foam, 0.45 g (72%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.28–7.25 (m, 2H), 7.22–7.19 (m, 1H), 7.09–7.07 (m, 2H), 6.70 (s, 1H), 4.03–4.01 (m, 2H), 3.68–3.65 (m, 2H), 2.91 (br, 4H), 1.94 (br, 2H), 1.39–1.34 (s, 11H), 1.20 (t, J = 7.0 Hz, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 155.23, 154.76, 136.61, 130.49, 128.00, 126.45, 79.44, 60.28, 53.64, 44.10, 39.76, 38.88, 34.29, 28.40, 14.70; ESI-HR-MS: (m/z) calcd. for C₂₀H₃₀N₂NaO₄ ([M+Na]⁺) 385.2098, found 385.2096.

General Procedure 3: Synthesis of C-1-1 to C-1-3 and C-2-1 to C-2-8. To a stirred solution of 72-1 to 72-3 or 72-2-1 to 72-2-8 (1.0 eq) in CH₂Cl₂, cooled to 0 °C, TFA (about 1.67 v/v based on CH₂Cl₂) was added dropwise. After addition, the reaction mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, and then evaporated on a rotary evaporator to afford a residue. Another flask, charged with 7·TFA (1.2 eq), EDCI (2.5 eq), HOBT (0.075 eq), DIPEA (6 eq), and dried THF, was stirred at 0 °C, followed by dropwise addition of a solution of the residue obtained above in a small amount of dried THF. After addition, the resulting mixture was stirred at room temperature overnight until TLC analysis indicated completion of the reaction, and then poured into water. The mixture thus obtained was extracted with EtOAc in three portions, and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography to afford the target products.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methanesulfonamide (C-1-1). Following General Procedure 3, 71-1 (0.90 g, 2.44 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.87 g, 2.93 mmol) using EDCI (1.22 g, 6.34 mmol), HOBT (25 mg, 0.183 mmol), and DIPEA (1.89 g, 14.6 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-1-1. White foam, 0.55 g (50%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.79–8.67 (m, 3H), 7.87–7.84 (m, 1H), 7.60–7.56 (m, 3H), 7.30–7.14 (m, 5H), 6.73–6.69 (m, 1H), 4.26–4.05 (m, 1H), 3.13–2.88 (m, 7H), 2.82–2.79 (m, 1H), 2.60–2.58 (m, 0.58H), 1.95–1.76 (m, 1H), 1.54–1.41 (m, 1.66H), 1.23–1.17 (m, 0.59H), 0.29–0.26 (m, 1H); ¹³C NMR (151 MHz, CDCl₃ + CD₃OD) δ 167.36, 167.19, 151.47, 151.37, 150.38, 150.30, 149.31, 146.48, 146.30, 136.10, 135.36, 135.12, 131.07, 130.93, 130.80, 130.73, 130.57, 127.97, 126.72, 126.65, 123.75, 123.66, 123.25, 123.12, 57.74, 57.64, 46.34, 45.49, 44.28, 42.78, 42.45, 37.42, 37.33, 33.86, 33.71, 33.46, 33.26; ESI-HR-MS: (m/z) calcd. for C₂₄H₂₇N₄O₃S ([M+H]⁺) 451.1798, found 451.1810.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)-1,1,1-trifluoromethanesulfonamide (C-1-2). Following General Procedure 3, 71-2 (1.10 g, 2.60 mmol) was first treated with TFA (5.5 mL) in CH₂Cl₂ (3.3 mL), and the intermediate obtained was reacted with 7·TFA (0.93 g, 3.12 mmol) using EDCI (1.25 g, 6.50 mmol), HOBT (26 mg, 0.195 mmol), and DIPEA (2.02 g, 15.6 mmol) in dried THF (11 mL). Purification by column chromatography (EtOAc) gave C-1-2. White foam, 0.64 g (49%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.78 (s, 1H), 8.65–8.56 (m, 2H), 7.87–7.84 (m, 1H), 7.55–7.51 (m, 3H), 7.34–7.11 (m, 6H), 4.26–4.14 (m, 1H), 3.06–2.92 (m, 2H), 2.88–2.72 (m, 2H), 2.66–2.54 (m, 1H), 2.02–1.91 (m, 0.69H), 1.78–1.52 (m, 1.78H), 1.38–1.23 (m, 1.60H), 0.71–0.42 (m, 0.45H); ¹³C NMR (151 MHz, CDCl₃) δ 167.61, 167.34, 167.28, 152.16, 151.59, 151.51, 150.66, 150.63, 150.05, 150.03, 149.92, 146.30, 146.27, 146.08, 136.28, 136.19, 136.06, 133.89, 133.67, 133.59, 131.14, 131.08, 130.84, 128.57, 128.52, 127.39, 127.33, 123.63, 123.56, 123.44, 122.72, 122.68, 57.23, 57.10, 57.02, 56.93, 49.75, 49.67, 49.54, 42.23, 42.13, 41.61, 41.47, 36.90, 36.71, 35.39, 34.96, 34.80, 34.39, 33.69, 33.37, 33.01, 32.93; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −76.07, −76.15, −76.38, −76.42; ESI-HR-MS: (m/z) calcd. for C₂₄H₂₄F₃N₄O₃S ([M+H]⁺) 505.1516, found 505.1516.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)ethanesulfonamide (C-1-3). Following General Procedure 3, 71-3 (0.60 g, 1.57 mmol) was first treated with TFA (3 mL) in CH₂Cl₂ (1.8 mL), and the intermediate obtained was reacted with 7·TFA (0.56 g, 1.88 mmol) using EDCI (0.75 g, 3.93 mmol), HOBT (16 mg, 0.118 mmol), and DIPEA (1.22 g, 9.42 mmol) in dried THF (11 mL). Purification by column chromatography (EtOAc) gave C-1-3. White foam, 0.33 g (45%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.78–8.77 (m, 1H), 8.68–8.66 (m, 2H), 7.87–7.85 (m, 1H), 7.59–7.55 (m, 3H), 7.28–7.15 (m, 5H), 6.64–6.58 (m, 1H), 4.24–4.03 (m, 1H), 3.09–2.89 (m, 5H), 2.88–2.80 (m, 1.4H), 2.67–2.55 (m, 1H), 1.95–1.74 (m, 1H), 1.52–1.40 (m, 2H), 1.22–1.17 (m, 2H), 1.10–1.07 (m, 1H), 0.28–0.23 (m, 0.52H); ¹³C NMR (151 MHz, CDCl₃) δ 167.54, 167.37, 151.92, 151.81, 150.71, 150.65, 150.11, 150.04, 146.32, 146.19, 136.26, 136.22, 135.25, 135.01, 131.17, 131.12, 131.00, 128.36, 127.07, 123.67, 123.61, 123.35, 123.07, 58.12, 58.07, 51.04, 50.99, 46.28, 45.40, 42.90, 42.48, 37.64, 37.58, 34.37, 34.30, 33.91, 33.66, 8.51; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₉N₄O₃S ([M+H]⁺) 465.1955, found 465.1954.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)acetamide (C-2-1). Following General Procedure 3, 72-1 (0.63 g, 1.90 mmol) was first treated with TFA (9.5 mL) in CH₂Cl₂ (5.7 mL), and the intermediate obtained was reacted with 7·TFA (0.68 g, 2.28 mmol) using EDCI (0.91 g, 4.75 mmol), HOBT (19 mg, 0.143 mmol), and DIPEA (1.47 g, 11.4 mmol) in dried THF (6.3 mL). Purification by column chromatography (EtOAc) gave C-2-1. White foam, 0.35 g (45%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.79–8.65 (m, 3H), 7.93–7.83 (m, 1H), 7.67–7.54 (m, 3H), 7.29–7.14 (m, 4H), 7.04–6.90 (m, 2H), 4.32–4.21 (m, 1H), 3.34 (s, 1H), 3.05–2.64 (m, 4.66H), 2.46–2.17 (m, 1H), 2.04–2.01 (m, 0.43H), 1.79–1.76 (m, 3H), 1.50–1.41 (m, 1H), 1.10–1.05 (d, 0.51H), 0.07–0.00 (m, 0.52H); ¹³C NMR (151 MHz, CDCl₃) δ 170.88, 170.78, 167.37, 167.19, 151.79, 151.51, 150.52, 150.45, 149.85, 149.79, 146.33, 146.26, 136.25, 136.17, 135.98, 135.94, 131.34, 131.11, 130.32, 130.27, 128.06, 128.03, 126.60, 126.56, 123.58, 123.54, 123.48, 122.94, 54.68, 54.44, 43.23, 42.95, 42.82, 42.42, 37.38, 33.92, 33.89, 33.42, 33.11, 24.11; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₇N₄O₂ ([M+H]⁺) 415.2129, found 415.2138.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)propionamide (C-2-2). Following General Procedure 3, 72-2 (1.23 g, 3.55 mmol) was first treated with TFA (6.2 mL) in CH₂Cl₂ (3.7 mL), and the intermediate obtained was reacted with 7·TFA (1.27 g, 4.26 mmol) using EDCI (1.70 g, 8.88 mmol), HOBT (36 mg, 0.266 mmol), and DIPEA (2.75 g, 21.3 mmol) in dried THF (12.3 mL). Purification by column chromatography (EtOAc) gave C-2-2. White foam, 0.71 g (47%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.79–8.77 (m, 2H), 8.65–8.64 (m, 1H), 7.93–7.83 (m, 1H), 7.68–7.66 (m, 1H), 7.58–7.53 (m, 2H), 7.27–7.24 (m, 2H), 7.20–7.17 (m, 1H), 7.08–7.01 (m, 2H), 6.91–6.89 (m, 1H), 4.32–4.21 (m, 1H), 3.02–2.67 (m, 5H), 2.46–2.18 (m, 1H), 2.05–2.00 (m, 2H), 1.84–1.81 (m, 0.37H), 1.53–1.49 (m, 1H), 1.42–1.03 (m, 1H), 1.00–0.94 (m, 3H), 0.06–0.01 (m, 0.54H); ¹³C NMR (151 MHz, CDCl₃) δ 174.24, 167.12, 166.84, 151.47, 151.14, 150.27, 150.22, 149.51, 146.07, 136.06, 135.98, 135.69, 131.10, 130.87, 130.16, 130.10, 127.74, 126.33, 123.35, 123.29, 122.67, 54.13, 53.86, 43.11, 42.89, 42.58, 42.17, 37.19, 33.66, 33.62, 33.28, 32.76, 29.99, 9.74; ESI-HR-MS: (m/z) calcd. for C₂₆H₂₉N₄O₂ ([M+H]⁺) 429.2285, found 429.2285.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)cyclopropanecarboxamide (C-2-3). Following General Procedure 3, 72-3 (0.60 g, 1.67 mmol) was first treated with TFA (3 mL) in CH₂Cl₂ (1.8 mL), and the intermediate obtained was reacted with 7·TFA (0.60 g, 2.00 mmol) using EDCI (0.80 g, 4.18 mmol), HOBT (17 mg, 0.125 mmol), and DIPEA (1.29 g, 10.0 mmol) in dried THF (6 mL). Purification by column chromatography (EtOAc) gave C-2-3. White foam, 0.45 g (61%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.79–8.65 (m, 3H), 7.94–7.84 (m, 1H), 7.67–7.54 (m, 3H), 7.41–7.37 (m, 1H), 7.28–7.18 (m, 3H), 7.04–6.90 (m, 2H), 4.32–4.22 (m, 1H), 3.07–2.67 (m, 4.40H), 2.46–1.80 (m, 2H), 1.59–1.44 (m, 2.42H), 1.12–1.07 (m, 0.52H), 0.72–0.58 (m, 4H), 0.12–0.06 (m, 0.53H); ¹³C NMR (151 MHz, CDCl₃) δ 173.99, 173.88, 167.10, 166.88, 151.53, 151.15, 150.25, 150.21, 149.52, 146.10, 136.11, 136.02, 135.77, 135.64, 131.16, 130.93, 130.28, 130.19, 127.78, 126.33, 123.38, 123.32, 122.71, 54.44, 54.10, 43.26, 43.10, 42.62, 42.32, 37.25, 33.95, 33.86, 33.43, 32.92, 14.71, 14.64, 6.69, 6.59, 6.53; ESI-HR-MS: (m/z) calcd. for C₂₇H₂₉N₄O₂ ([M+H]⁺) 441.2285, found 441.2284.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)pivalamide (C-2-4). Following General Procedure 3, 72-4 (1.50 g, 4.00 mmol) was first treated with TFA (7.5 mL) in CH₂Cl₂ (4.5 mL), and the intermediate obtained was reacted with 7·TFA (1.43 g, 4.80 mmol) using EDCI (1.92 g, 10.0 mmol), HOBT (41 mg, 0.300 mmol), and DIPEA (3.10 g, 24.0 mmol) in dried THF (15 mL). Purification by column chromatography (EtOAc) gave C-2-4. White foam, 0.30 g (16%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.79–8.77 (m, 2H), 8.63–8.62 (m, 1H), 7.93–7.84 (m, 1H), 7.68–7.67 (m, 1H), 7.59–7.51 (m, 2H), 7.26–7.17 (m, 3H), 7.00–6.88 (m, 2H), 6.23–6.14 (m, 1H), 4.33–4.22 (m, 1H), 2.95–2.55 (m, 4H), 2.47–2.10 (m, 2H), 1.93–1.65 (m, 1H), 1.46–1.24 (m, 1.47H), 1.06–1.00 (m, 9H), 0.04–0.01 (m, 0.53H); ¹³C NMR (126 MHz, CDCl₃) δ 178.50, 167.82, 152.04, 150.74, 150.10, 149.89, 146.57, 136.34, 136.16, 131.33, 130.63, 128.12, 126.84, 123.70, 123.22, 53.92, 43.44, 43.11, 42.44, 39.56, 37.60, 34.17, 33.80, 33.59, 31.70, 27.80, 22.77, 14.24; ESI-HR-MS: (m/z) calcd. for C₂₈H₃₃N₄O₂ ([M+H]⁺) 457.2598, found 457.2601.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)-2,2,2-trifluoroacetamide (C-2-5). Following General Procedure 3, 72-5 (0.90 g, 2.33 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.84 g, 2.80 mmol) using EDCI (1.12 g, 5.83 mmol), HOBT (24 mg, 0.175 mmol), and DIPEA (1.81 g, 14.0 mmol) in dried THF (15 mL). Purification by column chromatography (EtOAc) gave C-2-5. White foam, 0.66 g (60%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.80–8.52 (m, 4H), 7.96–7.85 (m, 1H), 7.67–7.53 (m, 3H), 7.30–7.22 (m, 3H), 7.03–6.91 (m, 2H), 4.33–4.24 (m, 1H), 3.35–3.34 (m, 0.53H), 3.11–2.54 (m, 5H), 2.30–2.15 (m, 1H), 1.90–1.71 (m, 1H), 1.66–1.56 (m, 0.75H), 1.25–0.22 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 171.27, 167.41, 167.20, 157.64 (q, J = 35.8 Hz), 151.75, 151.37, 150.61, 150.58, 149.68, 149.46, 146.28, 136.05, 135.91, 135.03, 134.92, 131.07, 130.82, 130.26, 130.20, 128.29, 127.01, 123.61, 123.50, 122.84, 115.37 (q, J = 289.6 Hz), 60.35, 56.13, 55.91, 43.02, 42.76, 42.63, 42.21, 37.26, 33.38, 33.25, 32.87, 32.59, 20.86, 14.05; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −73.73, −73.76; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₄F₃N₄O₂ ([M+H]⁺) 469.1846, found 469.1856.

N-(1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)-2,2-difluoroacetamide (C-2-6). Following General Procedure 3, 72-6 (0.10 g, 0.271 mmol) was first treated with TFA (0.5 mL) in CH₂Cl₂ (0.3 mL), and the intermediate obtained was reacted with 7·TFA (97 mg, 0.325 mmol) using EDCI (0.13 g, 0.676 mmol), HOBT (3 mg, 0.020 mmol), and DIPEA (0.21 g, 1.63 mmol) in dried THF (5 mL). Purification by column chromatography (EtOAc) gave C-2-6. White solid, 21 mg (17%). m.p. 97.9–99.4 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.80–8.78 (m, 2H), 8.65 (s, 1H), 8.10–8.06 (m, 1H), 7.95–7.84 (m, 1H), 7.67–7.54 (m, 3H), 7.29–7.20 (m, 3H), 7.04–6.91 (m, 2H), 6.17–5.92 (m, 1H), 4.34–4.24 (m, 1H), 3.11–3.08 (m, 0.44H), 2.97–2.94 (m, 2H), 2.84–2.63 (m, 2H), 2.22–2.07 (m, 1H), 1.83–1.53 (m, 2H), 1.27–1.15 (m, 2H), 0.87–0.84 (m, 1H), 0.16–0.12 (m, 0.53H); ¹³C NMR (126 MHz, CDCl₃) δ 167.56, 162.89, 162.70, 152.24, 151.85, 150.77, 150.28, 150.20, 146.38, 136.34, 136.23, 135.06, 131.37, 131.09, 130.44, 130.36, 128.51, 128.48, 127.22, 123.74, 123.65, 123.02, 110.58, 108.56, 108.38, 106.54, 55.56, 55.41, 43.50, 43.08, 42.82, 42.37, 37.43, 33.83, 33.33, 33.19, 29.81; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −124.47; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₅F₂N₄O₂ ([M+H]⁺) 451.1940, found 451.1940.

methyl (1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)carbamate (C-2-7). Following General Procedure 3, 72-7 (0.44 g, 1.27 mmol) was first treated with TFA (2.2 mL) in CH₂Cl₂ (1.3 mL), and the intermediate obtained was reacted with 7·TFA (0.45 g, 1.52 mmol) using EDCI (0.61 g, 3.18 mmol), HOBT (13 mg, 0.095 mmol), and DIPEA (0.98 g, 7.62 mmol) in dried THF (4.4 mL). Purification by column chromatography (EtOAc) gave C-2-7. White foam, 0.13 g (24%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.79–8.65 (m, 3H), 7.92–7.83 (m, 1H), 7.67–7.54 (m, 3H), 7.28–7.18 (m, 3H), 7.03–6.89 (m, 2H), 6.76–6.74 (m, 1H), 4.31–4.20 (m, 1H), 3.53 (s, 3H), 3.03–2.69 (m, 4.50H), 2.40–2.38 (m, 0.50H), 2.13–1.95 (m, 1H), 1.74–1.40 (m, 2H), 1.13–0.04 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.20, 167.09, 155.66, 151.84, 151.47, 150.38, 150.32, 149.83, 149.77, 146.15, 136.00, 135.94, 135.89, 135.85, 131.37, 131.06, 130.25, 130.18, 128.02, 127.98, 126.56, 126.50, 123.45, 123.41, 122.75, 53.55, 53.25, 51.70, 44.06, 43.94, 42.64, 42.27, 37.26, 34.15, 33.96, 33.55, 33.12; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₇N₄O₃ ([M+H]⁺) 431.2078, found 431.2077.

ethyl (1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)carbamate (C-2-8). Following General Procedure 3, 72-8 (0.95 g, 2.64 mmol) was first treated with TFA (13.2 mL) in CH₂Cl₂ (7.9 mL), and the intermediate obtained was reacted with 7·TFA (0.95 g, 3.17 mmol) using EDCI (1.27 g, 6.60 mmol), HOBT (27 mg, 0.198 mmol), and DIPEA (2.04 g, 15.8 mmol) in dried THF (9.5 mL). Purification by column chromatography (EtOAc) gave C-2-8. White foam, 0.64 g (55%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.79–8.65 (m, 3H), 7.92–7.82 (m, 1H), 7.67–7.54 (m, 3H), 7.27–7.18 (m, 3H), 7.05–6.90 (m, 2H), 6.70–6.67 (m, 1H), 4.31–4.20 (m, 1H), 4.03–3.95 (m, 2H), 3.03–2.69 (m, 4.5H), 2.41–2.37 (m, 0.54H), 2.15–1.98 (m, 1H), 1.77–1.39 (m, 2H), 1.18–1.15 (m, 3H), 1.10–1.07 (m, 0.58H), 0.09–0.02 (m, 0.51H); ¹³C NMR (151 MHz, CDCl₃) δ 167.01, 166.88, 155.16, 151.63, 151.24, 150.19, 150.14, 149.61, 149.54, 145.99, 135.89, 135.83, 135.81, 135.69, 131.23, 130.93, 130.12, 130.05, 127.81, 127.77, 126.35, 126.30, 123.31, 123.26, 122.58, 60.07, 53.36, 53.02, 43.88, 42.47, 42.15, 37.11, 34.03, 33.83, 33.42, 32.92, 14.44, 14.41; ESI-HR-MS: (m/z) calcd. for C₂₆H₂₉N₄O₃ ([M+H]⁺) 445.2234, found 445.2234.

Synthesis of tert-butyl 4-(aminomethyl)-4-benzylpiperidine-1-carboxylate (73). To a stirred solution of 68 (10.00 g, 33.3 mmol) in MeOH (100 mL), cooled to 0 °C under N₂, NiCl₂·6H₂O (15.8 g, 66.6 mmol) in one portion and NaBH₄ (12.6 g, 333 mmol) in portions were added successively. After addition, the reaction mixture was stirred at room temperature until completion, as indicated by TLC analysis (typically within 5 h), filtered through Celite, and poured into ice–water (100 mL). The resulting mixture was extracted with EtOAc (150 mL × 3), and the combined extracts were washed with brine, dried (MgSO₄), and evaporated on a rotary evaporator to afford a residue, which was purified by column chromatography (MeOH/CH₂Cl₂ = 1/10, by v/v) to give 73. Colorless oil, 8.88 g (88%). ¹H NMR (500 MHz, DMSO-d₆) δ 7.28–7.25 (m, 2H), 7.20–7.16 (m, 3H), 3.45–3.40 (m, 2H), 3.27–3.20 (m, 2H), 2.63 (s, 2H), 2.38 (s, 2H), 1.37 (s, 9H), 1.33–1.28 (m, 2H), 1.25–1.19 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 155.05, 137.68, 130.52, 128.16, 126.30, 79.45, 46.05, 41.13, 39.91, 39.24, 36.65, 32.16, 28.51; ESI-HR-MS: (m/z) calcd. for C₁₈H₂₉N₂O₂ ([M+H]⁺) 305.2224 found 305.2221.

Synthesis of tert-butyl 4-(acetamidomethyl)-4-benzylpiperidine-1-carboxylate (74-1). Compound 74-1 was prepared according to General Procedure 1 described above from 73 (0.80 g, 2.63 mmol) using AcCl (0.25 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 74-1. White solid, 0.85 g (95%). m.p. 48.2–50.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.26 (t, J = 6.0 Hz, 1H), 7.29–7.26 (m, 2H), 7.22–7.17 (m, 3H), 3.46–3.41 (m, 2H), 3.26 (s, 2H), 3.02 (d, J = 6.0 Hz, 2H), 2.61 (s, 2H), 1.89 (s, 3H), 1.35 (s, 9H), 1.26–1.17 (m, 4H); ¹³C NMR (126 MHz, CDCl₃) δ 170.23, 155.04, 137.49, 130.38, 128.58, 126.83, 79.57, 44.19, 44.00, 36.89, 32.59, 28.56, 23.47; ESI-HR-MS: (m/z) calcd. for C₂₀H₃₀N₂NaO₃ ([M+Na]⁺) 369.2149, found 369.2145.

Synthesis of tert-butyl 4-benzyl-4-(cyclopropanecarboxamidomethyl)piperidine-1-carboxylate (74-2). Compound 74-2 was prepared according to General Procedure 1 described above from 73 (0.80 g, 2.63 mmol) using cyclopropanecarbonyl chloride (0.33 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 74-2. White solid, 0.85 g (95%). White solid, 0.70 g (71%). m.p 66.6–69.2 °C. ¹H NMR (500 MHz, CDCl₃) δ 7.33–7.30 (m, 2H), 7.27–7.24 (m, 1H), 7.16–7.14 (m, 2H), 5.48 (t, J = 6.3 Hz, 1H), 3.59–3.56 (m, 2H), 3.39–3.17 (m, 4H), 2.65 (s, 2H), 1.44 (s, 9H), 1.43–1.41 (m, 3H), 1.21–1.16 (m, 1H), 0.91–0.88 (m, 2H), 0.71–0.67 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 173.79, 155.03, 137.52, 130.42, 128.52, 126.74, 79.48, 44.08, 43.96, 36.98, 32.51, 28.54, 14.84, 7.22; ESI-HR-MS: (m/z) calcd. for C₂₂H₃₂N₂NaO₃ ([M+Na]⁺) 395.2305, found 395.2304.

Synthesis of tert-butyl 4-benzyl-4-(pivalamidomethyl)piperidine-1-carboxylate (74-3). Compound 74-3 was prepared according to General Procedure 1 described above from 73 (0.80 g, 2.63 mmol) using pivaloyl chloride (0.38 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 74-3. White solid, 0.95 g (90%). m.p. 66–69 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.30–7.27 (m, 2H), 7.22–7.21 (m, 1H), 7.18–7.17 (m, 2H), 7.06 (t, J = 6.3 Hz, 1H), 3.36 (s, 4H), 3.08 (d, J = 6.0 Hz, 2H), 2.63 (s, 2H), 1.34 (s, 9H), 1.29–1.24 (m, 2H), 1.19–1.14 (m, 2H), 1.08 (s, 9H); ¹³C NMR (151 MHz, CDCl₃) δ 178.15, 154.74, 137.78, 130.02, 130.00, 128.66, 128.60, 126.73, 79.19, 45.50, 43.51, 43.49, 39.98, 38.94, 38.52, 37.17, 37.13, 32.78, 28.36, 28.33, 27.28, 27.25; ESI-HR-MS: (m/z) calcd. for C₂₃H₃₆N₂NaO₃ ([M+Na]⁺) 411.2618, found 411.2618.

Synthesis of tert-butyl 4-benzyl-4-((2,2,2-trifluoroacetamido)methyl)piperidine-1-carboxylate (74-4). Compound 74-4 was prepared according to General Procedure 2 from 73 (0.80 g, 2.63 mmol) using (CF₃CO)₂O (0.66 g, 3.16 mmol), DMAP (65 mg, 0.53 mmol), and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 74-4. White solid, 0.80 g (73%). m.p. 66–69 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 9.29 (t, J = 6.3 Hz, 1H), 7.30–7.27 (m, 2H), 7.23–7.17 (m, 3H), 3.41–3.37 (m, 4H), 3.20 (d, J = 6.0 Hz, 2H), 2.67 (s, 2H), 1.34 (s, 9H), 1.31–1.26 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 157.53 (q, J = 36.8 Hz), 154.87, 136.91, 130.07, 128.81, 127.14, 115.83 (q, J = 288.2 Hz), 79.69, 44.85, 43.93, 39.90, 38.95, 37.06, 32.41, 28.42; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −73.79; ESI-HR-MS: (m/z) calcd. for C₂₀H₂₇F₃N₂NaO₃ ([M+Na]⁺) 423.1866, found 423.1866.

Synthesis of tert-butyl 4-benzyl-4-((2,2-difluoroacetamido)methyl)piperidine-1-carboxylate (74-5). Compound 74-5 was prepared according to General Procedure 2 from 73 (0.80 g, 2.63 mmol) using (CHF₂CO)₂O (0.55 g, 3.16 mmol), DMAP (65 mg, 0.53 mmol), and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 74-5. White solid, 0.70 g (70%). m.p 66–69 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.67 (t, J = 6.3 Hz, 1H), 7.30–7.27 (m, 2H), 7.23–7.17 (m, 3H), 6.27 (t, J = 53.8 Hz, 1H), 3.44–3.40 (m, 2H), 3.33 (s, 2H), 3.14 (d, J = 6.0 Hz, 2H), 2.65 (s, 2H), 1.35 (s, 9H), 1.31–1.26 (m, 2H), 1.24–1.19 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 146.35 (t, J = 24.5 Hz), 154.88, 136.91, 130.13, 128.70, 127.00, 108.44 (t, J = 168.4 Hz), 79.60, 43.88, 43.81, 39.92, 38.97, 36.94, 32.43, 28.44; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −125.00; ESI-HR-MS: (m/z) calcd. for C₂₀H₂₈F₂N₂NaO₃ ([M+Na]⁺) 405.1960, found 405.1962.

Synthesis of tert-butyl 4-benzyl-4-((furan-2-carboxamido)methyl)piperidine-1-carboxylate (74-6). Compound 74-6 was prepared according to General Procedure 1 described above from 73 (0.80 g, 2.63 mmol) using furan-2-carbonyl chloride (0.41 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 74-6. Pale yellow foam, 0.92 g (88%). m.p. 66–69 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.12 (t, J = 6.3 Hz, 1H), 7.83–7.82 (m, 1H), 7.30–7.27 (m, 2H), 7.22–7.19 (m, 3H), 7.14 (d, J = 3.5 Hz, 1H), 6.62–6.61 (m, 1H), 3.44–3.46 (m, 4H), 3.26 (d, J = 6.5 Hz, 2H), 2.68 (s, 2H), 1.34–1.33 (m, 2H), 1.32 (s, 9H), 1.25–1.19 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 158.44, 154.83, 147.66, 143.80, 137.15, 130.20, 128.43, 126.56, 114.08, 112.06, 79.30, 43.89, 43.14, 39.95, 38.98, 37.05, 32.37, 28.34; ESI-HR-MS: (m/z) calcd. for C₂₃H₃₀N₂NaO₄ ([M+Na]⁺) 421.2098, found 421.2100.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)acetamide (C-3-1). Following General Procedure 3, 74-1 (0.85 g, 2.45 mmol) was first treated with TFA (4.3 mL) in CH₂Cl₂ (2.6 mL), and the intermediate obtained was reacted with 7·TFA (0.88 g, 2.94 mmol) using EDCI (1.18 g, 6.13 mmol), HOBT (25 mg, 0.184 mmol), and DIPEA (1.90 g, 14.7 mmol) in dried THF (8.5 mL). Purification by column chromatography (EtOAc) gave C-3-1. White solid, 0.15 g (14%). m.p. 146.3–148.5 °C. ¹H NMR (500 MHz, CD₃OD) δ 8.77 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.67–8.58 (m, 2H), 7.87–7.80 (m, 1H), 7.70–7.67 (m, 2H), 7.57 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 7.30–7.20 (m, 3H), 7.14–7.05 (m, 2H), 4.09–3.85 (m, 1H), 3.58–3.42 (m, 1H), 3.26–3.16 (m, 2H), 3.06–2.98 (m, 2H), 2.65 (s, 2H), 2.50–2.40 (m, 1H), 1.99 (s, 3H), 1.46–1.44 (m, 1H), 1.31–1.11 (m, 2H), 0.81–0.63 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 170.53, 170.22, 167.55, 167.39, 152.14, 151.88, 150.52, 150.46, 150.25, 150.19, 146.45, 146.30, 136.88, 136.78, 136.30, 136.13, 131.78, 131.62, 130.32, 130.00, 128.69, 128.56, 127.05, 126.92, 123.63, 123.58, 123.51, 123.32, 45.84, 44.30, 43.17, 42.96, 42.07, 37.65, 36.98, 36.90, 32.33, 32.29, 31.73, 31.45, 23.36, 23.30; ESI-HR-MS: (m/z) calcd. for C₂₆H₂₉N₄O₂ ([M+H]⁺) 429.2286, found 429.2283.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)cyclopropanecarboxamide (C-3-2). Following General Procedure 3, 74-2 (0.70 g, 1.88 mmol) was first treated with TFA (3.5 mL) in CH₂Cl₂ (2.1 mL), and the intermediate obtained was reacted with 7·TFA (0.67 g, 2.26 mmol) using EDCI (0.90 g, 4.70 mmol), HOBT (19 mg, 0.141 mmol), and DIPEA (1.46 g, 11.3 mmol) in dried THF (7 mL). Purification by column chromatography (EtOAc) gave C-3-2. White solid, 0.47 g (55%). m.p. 161.5–162.3 °C. ¹H NMR (500 MHz, CD₃OD) δ 8.77 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.67–8.58 (m, 2H), 7.86–7.80 (m, 1H), 7.70–7.67 (m, 2H), 7.56 (dd, J = 5.0 Hz and 7.5 Hz, 1H), 7.30–7.20 (m, 3H), 7.15–7.06 (m, 2H), 4.08–3.84 (m, 1H), 3.62–3.35 (m, 1.53H), 3.26–3.22 (m, 2H), 3.05–2.99 (m, 2H), 2.68–2.43 (m, 2H), 1.72–1.67 (m, 1H), 1.46–1.44 (m, 1H), 1.34–1.12 (m, 2H), 0.85–0.75 (m, 4H), 0.69–0.64 (m, 0.56H); ¹³C NMR (126 MHz, CDCl₃) δ 174.22, 173.87, 167.45, 167.39, 152.03, 151.86, 150.52, 150.43, 150.29, 150.17, 146.43, 146.35, 136.94, 136.82, 136.30, 136.23, 131.78, 131.67, 130.36, 130.05, 128.67, 128.52, 127.00, 126.85, 123.61, 123.49, 123.42, 45.81, 44.71, 43.22, 43.01, 42.41, 42.08, 37.65, 37.10, 36.96, 32.37, 32.18, 31.32, 31.17, 14.70, 14.64, 7.51, 7.43, 7.28; ESI-HR-MS: (m/z) calcd. for C₂₈H₃₁N₄O₂ ([M+H]⁺) 455.2442, found 455.2448.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)pivalamide (C-3-3). Following General Procedure 3, 74-3 (0.83 g, 2.14 mmol) was first treated with TFA (4.2 mL) in CH₂Cl₂ (2.4 mL), and the intermediate obtained was reacted with 7·TFA (0.77 g, 2.57 mmol) using EDCI (1.03 g, 5.35 mmol), HOBT (22 mg, 0.161 mmol), and DIPEA (1.65 g, 12.8 mmol) in dried THF (8.3 mL). Purification by column chromatography (EtOAc) gave C-3-3. White foam, 0.62 g (62%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77–8.76 (m, 1H), 8.66–8.58 (m, 2H), 7.79–7.73 (m, 1H), 7.59–7.53 (m, 3H), 7.30–7.16 (m, 4H), 7.10–6.94 (m, 2H), 3.86–3.75 (m, 1H), 3.48–3.40 (m, 1H), 3.21–2.94 (m, 4H), 2.63–2.56 (m, 0.85H), 2.47–2.40 (m, 1.21H), 1.37–1.12 (m, 3H), 1.07 (s, 9H), 0.86–0.61 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 178.19, 167.12, 166.97, 151.90, 151.37, 150.09, 149.82, 149.77, 146.14, 145.91, 137.11, 137.06, 135.98, 135.55, 131.47, 131.24, 129.78, 129.56, 128.60, 128.53, 126.82, 126.76, 123.35, 123.25, 123.14, 122.69, 47.00, 45.31, 42.93, 42.87, 42.69, 41.75, 38.38, 38.30, 37.52, 37.34, 37.17, 37.04, 32.83, 32.48, 32.05, 31.87, 27.12, 27.02; ESI-HR-MS: (m/z) calcd. for C₂₉H₃₅N₄O₂ ([M+H]⁺) 471.2755, found 471.2761.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-2,2,2-trifluoroacetamide (C-3-4). Following General Procedure 3, 74-4 (0.72 g, 1.80 mmol) was first treated with TFA (3.6 mL) in CH₂Cl₂ (2.2 mL), and the intermediate obtained was reacted with 7·TFA (0.64 g, 2.16 mmol) using EDCI (0.86 g, 4.50 mmol), HOBT (18 mg, 0.135 mmol), and DIPEA (1.40 g, 10.8 mmol) in dried THF (7.2 mL). Purification by column chromatography (EtOAc) gave C-3-4. White solid, 0.48 g (55%). ¹H NMR (500 MHz, DMSO-d₆) δ 9.30–9.22 (m, 1H), 8.78–8.76 (m, 1H), 8.65–8.56 (m, 2H), 7.82–7.74 (m, 1H), 7.58–7.52 (m, 3H), 7.30–7.09 (m, 5H), 3.82–3.68 (m, 1H), 3.60–3.46 (m, 1H), 3.39–3.37 (m, 2H), 3.22–3.16 (m, 2H), 3.06–2.97 (m, 1.60H), 2.69–2.53 (m, 1H), 2.49–2.46 (m, 0.46H), 1.40–1.12 (m, 3H), 0.84–0.73 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.31, 167.19, 157.98, 157.73, 157.49, 157.24, 151.50, 150.29, 149.70, 146.16, 146.10, 136.07, 135.98, 135.85, 135.68, 131.14, 131.08, 129.97, 129.77, 128.52, 128.45, 126.99, 126.89, 123.41, 123.35, 123.12, 122.90, 118.48, 116.61, 116.57, 114.70, 114.66, 44.46, 44.32, 43.25, 42.76, 42.68, 42.48, 37.32, 37.27, 36.88, 36.80, 31.66, 31.62, 31.54, 31.20; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −73.66, −73.71; ESI-HR-MS: (m/z) calcd. for C₂₆H₂₆F₃N₄O₂ ([M+H]⁺) 483.2002, found 483.2007.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-2,2-difluoroacetamide (C-3-5). Following general procedure 3, 74-5 (0.57 g, 1.49 mmol) was first treated with TFA (2.9 mL) in CH₂Cl₂ (1.7 mL), and the intermediate obtained was reacted with 7·TFA (0.53 g, 1.79 mmol) using EDCI (0.72 g, 3.73 mmol), HOBT (15 mg, 0.112 mmol), and DIPEA (1.16 g, 8.94 mmol) in dried THF (5.7 mL). Purification by column chromatography (EtOAc) gave C-3-5. White foam, 0.33 g (48%). ¹H NMR (500 MHz, CD₃OD) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.66–8.65 (m, 1H), 8.56–8.55 (m, 1H), 7.86–7.79 (m, 1H), 7.69–7.64 (m, 2H), 7.56 (dd, J = 4.8 Hz and 7.8 Hz, 1H), 7.31–7.22 (m, 3H), 7.15–7.06 (m, 2H), 6.21–5.97 (m, 1H), 4.03–3.81 (m, 1H), 3.65–3.45 (m, 1H), 3.35–3.32 (m, 1H), 3.28–3.20 (m, 1H), 3.12–3.00 (m, 2H), 2.68 (s, 1H), 2.55–2.47 (m, 1H), 1.50–1.47 (m, 1H), 1.34–1.17 (m, 2H), 0.81–0.75 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.30, 167.13, 163.22, 163.11, 163.06, 162.94, 162.89, 162.78, 151.66, 151.47, 150.22, 149.71, 146.11, 146.01, 136.08, 135.99, 135.86, 135.76, 131.19, 131.12, 129.98, 129.76, 128.42, 128.33, 126.85, 126.73, 123.37, 123.11, 122.92, 109.95, 109.79, 108.28, 108.13, 106.62, 106.46, 44.29, 43.91, 42.69, 42.47, 42.17, 37.28, 36.72, 36.65, 31.69, 31.54, 31.45, 30.97; ¹⁹F NMR (471 MHz, CD₃OD) δ −127.59; ESI-HR-MS: (m/z) calcd. for C₂₆H₂₇F₂N₄O₂ ([M+H]⁺) 465.2097, found 465.2104.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)furan-2-carboxamide (C-3-6). Following General Procedure 3, 74-6 (0.78 g, 1.96 mmol) was first treated with TFA (9.8 mL) in CH₂Cl₂ (5.9 mL), and the intermediate obtained was reacted with 7·TFA (0.70 g, 2.35 mmol) using EDCI (0.94 g, 4.90 mmol), HOBT (20 mg, 0.147 mmol), and DIPEA (1.53 g, 11.8 mmol) in dried THF (7.8 mL). Purification by column chromatography (EtOAc) gave C-3-6. White solid, 0.39 g (41%). ¹H NMR (500 MHz, CD₃OD) δ 8.76 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.56–8.53 (m, 2H), 7.86–7.77 (m, 1H), 7.67–7.63 (m, 3H), 7.55 (dd, J = 5.0 Hz and 8.0 Hz, 1H), 7.31–7.23 (m, 3H), 7.19–7.09 (m, 3H), 6.59–6.58 (m, 1H), 4.06–3.88 (m, 1H), 3.62–3.50 (m, 1H), 3.44–3.41 (m, 1H), 3.35–3.33 (m, 1H), 3.27 (s, 1.44H), 3.11–3.08 (m, 1H), 2.74 (s, 0.56H), 2.60–2.52 (m, 1H), 1.56–1.24 (m, 3H), 1.08–0.79 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.00, 166.86, 158.26, 158.19, 151.64, 151.32, 149.92, 149.60, 147.15, 147.04, 145.93, 145.77, 143.72, 136.33, 136.28, 135.74, 135.41, 131.24, 131.08, 129.89, 129.66, 128.22, 128.13, 126.44, 126.37, 123.15, 123.03, 122.97, 122.60, 113.87, 111.75, 44.94, 43.11, 42.77, 42.72, 42.53, 41.27, 37.30, 37.19, 36.93, 36.82, 31.84, 31.66, 31.35; ESI-HR-MS: (m/z) calcd. for C₂₉H₂₉N₄O₃ ([M+H]⁺) 481.2234, found 481.2239.

Synthesis of tert-butyl 4-benzyl-4-(methylsulfonamidomethyl)piperidine-1-carboxylate (75-1). Compound 75-1 was prepared according to General Procedure 2 from 73 (0.80 g, 2.63 mmol) using Ms₂O (0.55 g, 3.16 mmol), DMAP (65 mg, 0.53 mmol), and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/2, by v/v) gave 75-1. White solid, 0.35 g (35%). m.p 160.2–162.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.29–7.26 (m, 2H), 7.22–7.18 (m, 3H), 6.99 (t, J = 6.8 Hz, 1H), 3.46–3.41 (m, 2H), 3.26 (s, 2H), 2.91 (s, 3H), 2.86 (d, J = 7.0 Hz, 2H), 2.63 (s, 2H), 1.36 (s, 9H), 1.35–1.33 (m, 2H), 1.24–1.19 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 154.98, 136.73, 130.44, 128.52, 126.87, 79.68, 47.75, 42.22, 39.93, 36.32, 32.21, 28.52; ESI-HR-MS: (m/z) calcd. for C₁₉H₃₀N₂NaO₄S ([M+Na]⁺) 405.1818, found 405.1815.

Synthesis of tert-butyl 4-benzyl-4-(((trifluoromethyl)sulfonamido)methyl)piperidine-1-carboxylate (75-2). Compound 75-2 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using TfCl (0.53 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-2. White solid, 0.65 g (57%). m.p 161.3–162.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 9.33 (t, J = 6.0 Hz, 1H), 7.31–7.28 (m, 2H), 7.24–7.20 (m, 1H), 7.18–7.16 (m, 2H), 3.43–3.38 (m, 2H), 3.33–3.30 (m, 2H), 3.05 (d, J = 6.0 Hz, 2H), 2.70 (s, 2H), 1.40–1.38 (m, 2H), 1.36 (s, 9H), 1.27–1.22 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 154.99, 136.34, 130.29, 128.85, 127.27, 121.15, 118.59, 80.08, 49.76, 42.39, 36.47, 31.86, 28.50; ESI-HR-MS: (m/z) calcd. for C₁₉H₂₇F₃N₂NaO₄S ([M+Na]⁺) 459.1536, found 459.1530.

Synthesis of tert-butyl 4-benzyl-4-(ethylsulfonamidomethyl)piperidine-1-carboxylate (75-3). Compound 75-3 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using CH₃CH₂SO₂Cl (0.41 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-3. White solid, 0.75 g (72%). m.p. 124.6–126.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.29–7.26 (m, 2H), 7.21–7.19 (m, 3H), 7.04 (t, J = 6.8 Hz, 1H), 3.45–3.34 (m, 2H), 3.25 (s, 2H), 3.04–3.00 (m, 2H), 2.84 (d, J = 6.5 Hz, 2H), 2.64 (s, 2H), 1.38–1.36 (m, 2H), 1.35 (s, 9H), 1.23–1.19 (m, 5H); ¹³C NMR (126 MHz, CDCl₃) δ 155.02, 136.82, 130.36, 128.67, 127.02, 79.74, 47.73, 46.72, 42.76, 36.54, 32.39, 28.57, 8.45; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₃N₂O₄S ([M+H]⁺) 397.2156, found 397.2158.

Synthesis of tert-butyl 4-benzyl-4-(cyclopropanesulfonamidomethyl)piperidine-1-carboxylate (75-4). Compound 75-4 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using cyclopropanesulfonyl chloride (0.44 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-4. White solid, 0.55 g (51%). m.p 66.3–69.7 °C. ¹H NMR (500 MHz, CDCl₃) δ 7.32–7.29 (m, 2H), 7.27–7.23 (m, 1H), 7.17–7.15 (m, 2H), 4.48 (t, J = 6.8 Hz, 1H), 3.60–3.55 (m, 2H), 3.39–3.34 (m, 2H), 3.04–3.02 (m, 2H), 2.68 (s, 2H), 2.41–2.36 (m, 1H), 1.50–1.48 (m, 4H), 1.45 (s, 9H), 1.17–1.13 (m, 2H), 1.00–0.96 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 154.99, 136.83, 130.46, 128.53, 126.87, 79.67, 47.72, 42.38, 36.35, 32.31, 29.75, 28.54, 5.39; ESI-HR-MS: (m/z) calcd. for C₂₁H₃₂N₂NaO₄S ([M+Na]⁺) 431.1975, found 431.1971.

Synthesis of tert-butyl 4-benzyl-4-((thiophene-2-sulfonamido)methyl)piperidine-1-carboxylate (75-5). Compound 75-5 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using thiophene-2-sulfonyl chloride (0.58 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-5. White solid, 1.02 g (86%). m.p 131.2–131.7 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.94 (dd, J = 1.0 Hz and 5.0 Hz, 1H), 7.85 (t, J = 6.5 Hz, 1H), 7.60 (dd, J = 1.3 Hz and 3.8 Hz, 1H), 7.23–7.16 (m, 4H), 7.11–7.09 (m, 2H), 3.43–3.33 (m, 2H), 3.18 (s, 2H), 2.71 (d, J = 6.5 Hz, 2H), 2.64 (s, 2H), 1.35 (s, 9H), 1.33–1.31 (m, 2H), 1.24–1.19 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.92, 140.51, 136.58, 132.28, 132.05, 130.41, 128.40, 127.57, 126.73, 79.63, 47.63, 42.39, 39.79, 38.88, 36.10, 32.32, 28.50; ESI-HR-MS: (m/z) calcd. for C₂₂H₃₀N₂NaO₄S₂ ([M+Na]⁺) 473.1539, found 473.1540.

Synthesis of tert-butyl 4-benzyl-4-((pyridine-3-sulfonamido)methyl)piperidine-1-carboxylate (75-6). Compound 75-6 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using pyridine-3-sulfonyl chloride (0.56 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-6. White solid, 1.02 g (87%). m.p. 160.5–161.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.97 (d, J = 2.5 Hz, 1H), 8.83 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.21–8.19 (m, 1H), 7.87 (t, J = 6.0 Hz, 1H), 7.66 (dd, J = 5.0 Hz and 8.0 Hz, 1H), 7.22–7.15 (m, 3H), 7.10–7.08 (m, 2H), 3.44–3.39 (m, 2H), 3.18 (s, 2H), 2.68 (d, J = 5.5 Hz, 2H), 2.63 (s, 2H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.83, 153.17, 147.83, 136.52, 136.40, 134.71, 130.29, 128.29, 126.67, 123.86, 79.61, 47.68, 41.96, 39.70, 38.80, 36.10, 31.95, 28.38; ESI-HR-MS: (m/z) calcd. for C₂₃H₃₁N₃NaO₄S ([M+Na]⁺) 468.1927, found 468.1931.

Synthesis of tert-butyl 4-benzyl-4-(((phenylmethyl)sulfonamido)methyl)piperidine-1-carboxylate (75-7). Compound 75-7 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using phenylmethanesulfonyl chloride (0.60 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-7. White solid, 0.72 g (60%). m.p. 150.5–151.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.41–7.35 (m, 5H), 7.29–7.26 (m, 2H), 7.22–7.19 (m, 1H), 7.16–7.11 (m, 3H), 4.36 (s, 2H), 3.43–3.38 (m, 2H), 3.23 (s, 2H), 2.72 (d, J = 7.0 Hz, 2H), 2.57 (s, 2H), 1.36 (s, 9H), 1.33–1.28 (m, 2H), 1.19–1.13 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.93, 136.68, 130.60, 130.32, 129.33, 129.03, 128.94, 128.43, 126.73, 79.56, 58.74, 47.79, 42.47, 39.78, 38.88, 36.49, 36.48, 32.10, 32.07, 28.51; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₄N₂NaO₄S ([M+Na]⁺) 481.2131, found 481.2130.

Synthesis of tert-butyl 4-benzyl-4-(phenylsulfonamidomethyl)piperidine-1-carboxylate (75-8). Compound 75-8 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using benzenesulfonyl chloride (0.56 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-8. White solid, 0.72 g (62%). m.p. 76.5–77.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.83–7.81 (m, 2H), 7.67–7.59 (m, 4H), 7.21–7.14 (m, 3H), 7.09–7.07 (m, 2H), 3.43–3.32 (m, 2H), 3.15 (s, 2H), 2.62–2.61 (m, 4H), 1.35 (s, 9H), 1.31–1.29 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 154.97, 139.62, 136.67, 132.95, 130.37, 129.36, 128.51, 127.14, 126.85, 79.70, 47.50, 42.68, 36.25, 32.46, 28.55; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₃N₂O₄S ([M+H]⁺) 445.2156, found 445.2151.

Synthesis of tert-butyl 4-benzyl-4-(((4-fluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-9). Compound 75-9 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-fluorobenzenesulfonyl chloride (0.61 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-9. White solid, 1.10 g (90%). m.p. 176.4–177.8 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.89–7.87 (m, 2H), 7.67 (t, J = 6.5 Hz, 1H), 7.45 (t, J = 8.8 Hz, 2H), 7.22–7.15 (m, 3H), 7.09–7.08 (m, 2H), 3.43–3.39 (m, 2H), 3.17–3.15 (m, 2H), 2.62–2.61 (m, 4H), 1.35 (s, 9H), 1.33–1.28 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 166.03, 164.34, 154.93, 136.59, 135.73 (d, J = 3.2 Hz), 130.36, 129.84 (d, J = 9.4 Hz), 128.43, 126.81, 116.54 (d, J = 22.5 Hz), 79.68, 47.52, 42.36, 36.18, 32.33, 28.50; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −107.10; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₁FN₂NaO₄S ([M+Na]⁺) 485.1881, found 485.1880.

Synthesis of tert-butyl 4-benzyl-4-(((4-cyanophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-10). Compound 75-10 was prepared according to General Procedure 1 from 73 (1.00 g, 3.28 mmol) using 4-cyanobenzenesulfonyl chloride (0.79 g, 3.94 mmol) and Et₃N (1.00 g, 9.84 mmol) in dried CH₂Cl₂ (10 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-10. White foam, 1.10 g (73%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.12–8.10 (m, 2H), 7.99–7.97 (m, 2H), 7.92 (t, J = 6.3 Hz, 1H), 7.22–7.15 (m, 3H), 7.10–7.08 (m, 2H), 3.43–3.39 (m, 2H), 3.17–3.15 (m, 2H), 2.67–2.62 (m, 4H), 1.35 (s, 9H), 1.32–1.29 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.94, 144.08, 136.50, 133.13, 130.29, 128.57, 127.73, 127.01, 117.35, 116.57, 79.84, 48.03, 42.37, 39.75, 38.94, 36.33, 32.26, 28.51; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₁N₃NaO₄S ([M+Na]⁺) 492.1927, found 492.1926.

Synthesis of tert-butyl 4-benzyl-4-(((4-methoxyphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-11). Compound 75-11 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-methoxybenzenesulfonyl chloride (0.65 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-11. White solid, 0.99 g (79%). m.p. 113.1–114.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.75 (d, J = 10.0 Hz, 2H), 7.47 (t, J = 6.5 Hz, 1H), 7.21–7.16 (m, 3H), 7.13–7.07 (m, 4H), 3.84 (s, 3H), 3.43–3.33 (m, 2H), 3.14 (s, 2H), 2.62–2.57 (m, 4H), 1.35 (s, 9H), 1.30–1.28 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 163.01, 154.90, 136.69, 131.15, 130.44, 129.25, 128.30, 126.62, 114.42, 79.54, 55.70, 47.20, 42.32, 39.74, 38.92, 36.08, 32.33, 28.48; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₄N₂NaO₅S ([M+Na]⁺) 497.2081, found 497.2078.

Synthesis of tert-butyl 4-benzyl-4-(((4-nitrophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-12). Compound 75-12 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-nitrobenzenesulfonyl chloride (0.70 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-12. White solid, 1.10 g (85%). m.p. 164.1–164.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.45–8.42 (m, 2H), 8.09–7.99 (m, 2H), 7.71 (t, J = 6.5 Hz, 1H), 7.22–7.15 (m, 3H), 7.11–7.09 (m, 2H), 3.44–3.39 (m, 2H), 3.20–3.15 (m, 2H), 2.69 (d, J = 6.5 Hz, 2H), 2.63 (s, 2H), 1.34 (s, 9H), 1.32–1.30 (m, 2H), 1.24–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.95, 150.19, 145.64, 136.50, 130.29, 128.58, 128.36, 127.02, 124.56, 79.86, 48.17, 42.34, 39.76, 38.95, 36.35, 32.23, 28.51; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₁N₃NaO₆S ([M+Na]⁺) 512.1826, found 512.1830.

Synthesis of tert-butyl 4-benzyl-4-(((3-chlorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-13). Compound 75-13 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3-chlorobenzenesulfonyl chloride (0.67 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-13. White solid, 1.10 g (87%). m.p. 185.2–185.8 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.84 (t, J = 1.8 Hz, 1H), 7.79–7.74 (m, 3H), 7.65 (t, J = 8.0 Hz, 1H), 7.22–7.15 (m, 3H), 7.10–7.08 (m, 2H), 3.44–3.39 (m, 2H), 3.17–3.15 (m, 2H), 2.65–2.63 (m, 4H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.94, 141.43, 136.58, 135.54, 133.01, 130.63, 130.35, 128.51, 127.20, 126.89, 125.19, 79.71, 47.67, 42.52, 39.81, 38.94, 36.25, 32.37, 28.53; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₁ClN₂NaO₄S ([M+Na]⁺) 501.1585, found 501.1586.

Synthesis of tert-butyl 4-benzyl-4-(((2-fluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-14). Compound 75-14 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2-fluorobenzenesulfonyl chloride (0.61 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-14. White solid, 1.06 g (87%). m.p. 161.3–162.6 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.97 (s, 1H), 7.81–7.78 (m, 1H), 7.73–7.69 (m, 1H), 7.48–7.44 (m, 1H), 7.40–7.37 (m, 1H), 7.24–7.21 (m, 2H), 7.19–7.16 (m, 1H), 7.12–1.10 (m, 2H), 3.42–3.38 (m, 2H), 3.16 (s, 2H), 2.76 (s, 2H), 2.65 (s, 2H), 1.35 (s,9H), 1.33–1.30 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (126 MHz, DMSO-d₆) δ 159.14, 157.13, 153.93, 137.09, 135.24 (d, J = 8.4 Hz), 130.63, 129.78, 128.31 (d, J = 14.2 Hz), 127.79, 126.09, 124.91 (d, J = 3.7 Hz), 117.26 (d, J = 21.3 Hz), 78.49, 47.07, 40.67, 35.53, 30.92, 28.05; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −110.11; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₁FN₂NaO₄S ([M+Na]⁺) 485.1881, found 485.1881.

Synthesis of tert-butyl 4-benzyl-4-(((3-fluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-15). Compound 75-15 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3-fluorobenzenesulfonyl chloride (0.61 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-15. White solid, 1.04 g (86%). m.p. 151.0–152.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.76 (s, 1H), 7.70–7.66 (m, 2H), 7.63–7.61 (m, 1H), 7.55–7.51 (m, 1H), 7.22–7.15 (m, 3H), 7.10–7.08 (m, 2H), 3.44–3.40 (m, 2H), 3.17 (s, 2H), 2.65–2.62 (m, 4H), 1.35 (s, 9H), 1.32–1.29 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 163.41, 161.74, 154.94, 141.75 (d, J = 6.5 Hz), 136.57, 131.16 (d, J = 7.7 Hz), 130.36, 128.45, 126.84, 122.85, 122.83, 120.09 (d, J = 21.3 Hz), 114.50 (d, J = 24.3 Hz), 79.70, 47.64, 42.40, 39.79, 38.91, 36.22, 32.32, 28.51; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −110.62; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₁FN₂NaO₄S ([M+Na]⁺) 485.1881, found 485.1881.

Synthesis of tert-butyl 4-benzyl-4-(((perfluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-16). Compound 75-16 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using perfluorobenzenesulfonyl chloride (0.84 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-16. White solid, 1.04 g (74%). m.p. 170.1–170.8 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.72 (s, 1H), 7.28–7.24 (m, 2H), 7.22–7.16 (m, 3H), 3.44–3.39 (m, 2H), 3.24 (s, 2H), 2.89 (s, 2H), 2.68 (s, 2H), 1.37–1.35 (m, 11H), 1.26–1.21 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.95, 145.12 (t, J = 35.0 Hz), 143.40 (t, J = 37.4 Hz), 138.85 (d, J = 12.5 Hz), 137.19 (t, J = 17.8 Hz), 136.52, 130.20, 128.80, 127.24, 116.14 (t, J = 15.3 Hz), 79.86, 48.14, 46.01, 42.97, 39.74, 38.90, 36.54, 32.50, 28.55; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −137.97–−138.07 (m), −148.02 (tt, J = 5.7 and 22.6 Hz), −159.92–−160.05 (m); ESI-HR-MS: (m/z) calcd. for C₂₄H₂₇F₅N₂NaO₄S ([M+Na]⁺) 557.1504, found 557.1505.

Synthesis of tert-butyl 4-benzyl-4-(((2,3,4,5,6-pentamethylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-17). Compound 75-17 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2,3,4,5,6-pentamethylbenzenesulfonyl chloride (0.78 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-17. White solid, 1.01g (75%). m.p. 177.5–178.0 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.39 (t, J = 6.5 Hz, 1H), 7.22–7.15 (m, 3H), 7.07–7.06 (m, 2H), 3.37–3.36 (m, 2H), 3.13–3.08 (m, 2H), 2.61–2.59 (m, 4H), 2.48 (s, 6H), 2.23 (s, 3H), 2.18 (s, 6H), 1.34 (s, 9H), 1.32–1.27 (m, 2H), 1.17–1.12 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.93, 139.73, 136.95, 135.72, 134.99, 134.11, 130.41, 128.46, 126.78, 79.61, 46.93, 42.70, 39.82, 38.97, 36.31, 32.55, 28.54, 19.01, 17.89, 17.17; ESI-HR-MS: (m/z) calcd. for C₂₉H₄₂N₂NaO₄S ([M+Na]⁺) 537.2757, found 537.2759.

Synthesis of tert-butyl 4-benzyl-4-(((3,4-difluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-18). Compound 75-18 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3,4-difluorobenzenesulfonyl chloride (0.67 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/5, by v/v) gave 75-18. White solid, 1.09 g (86%). m.p. 185.9–186.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.89–7.86 (m, 1H), 7.77 (s, 1H), 7.72–7.69 (m, 2H), 7.23–7.16 (m, 3H), 7.11–7.09 (m, 2H), 3.43–3.39 (m, 2H), 3.18 (s, 2H), 2.66–2.62 (m, 4H), 1.35 (s, 9H), 1.32–1.29 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (151 MHz, DMSO-d₆) δ 153.95, 152.68 (d, J = 12.4 Hz), 151.00 (d, J = 12.4 Hz), 150.06 (d, J = 13.4 Hz), 148.40 (d, J = 13.3 Hz), 137.34 (t, J = 4.2 Hz), 130.64, 127.72, 126.09, 124.40 (q, J = 3.9 Hz), 118.63 (d, J = 18.3 Hz), 116.44 (d, J = 19.6 Hz), 78.43, 67.00, 46.97, 40.83, 35.51, 28.01; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₀F₂N₂NaO₄S ([M+Na]⁺) 503.1787, found 503.1787.

Synthesis of tert-butyl 4-benzyl-4-(((3,4,5-trifluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-19). Compound 75-19 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3,4,5-trifluorobenzenesulfonyl chloride (0.73 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-19. White solid, 1.03 g (79%). m.p. 197.9–198.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.86 (s, 1H), 7.77 (t, J = 6.5 Hz, 2H), 7.24–7.12 (m, 3H), 7.14–7.12 (m, 2H), 3.45–3.40 (m, 2H), 3.19 (s, 2H), 2.70 (s, 2H), 2.62 (s, 2H), 1.35 (s, 9H), 1.33–1.30 (m, 2H), 1.24–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.98, 151.27 (ddd, J = 3.2, 10.6 and 257.2 Hz), 142.789 (dt, J = 15.0 and 185.4 Hz), 136.57, 135.96 (q, J = 5.6 Hz), 130.28, 128.69, 127.16, 112.31 (dd, J = 5.6 and 18.3 Hz), 79.91, 48.29, 42.61, 39.80, 38.99, 36.39, 32.41, 28.54; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −131.39 (d, J = 21.2 Hz), −154.40 (d, J = 21.2 Hz); ESI-HR-MS: (m/z) calcd. for C₂₄H₂₉F₃N₂NaO₄S ([M+Na]⁺) 521.1692, found 521.1694.

Synthesis of tert-butyl 4-benzyl-4-(((2,5-difluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-20). Compound 75-20 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2,5-difluorobenzenesulfonyl chloride (0.67 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-20. White solid, 1.07 g (85%). m.p. 155.5–156.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.12 (t, J = 6.0 Hz, 1H), 7.62–7.53 (m, 3H), 7.24–7.21 (m, 2H), 7.19–7.16 (m, 1H), 7.13–7.11 (m, 2H), 3.43–3.38 (m, 2H), 3.19 (s, 2H), 2.79 (d, J = 5.5 Hz, 2H), 1.35 (s, 9H), 1.33–1.31 (m, 2H), 1.24–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 157.96 (dd, J = 2.5 and 248.5 Hz), 154.88, 136.55, 130.32, 128.99 (dd, J = 6.7 and 16.2 Hz), 128.48, 126.84, 121.66 (dd, J = 8.5 and 24.1 Hz), 118.45 (dd, J = 7.9 and 24.3 Hz), 117.37, 117.19, 79.64, 47.52, 42.48, 39.73, 38.85, 36.24, 32.25, 28.48; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −115.64 (d, J = 18.8 Hz), −116.31 (d, J = 18.8 Hz); ESI-HR-MS: (m/z) calcd. for C₂₄H₃₀F₂N₂NaO₄S ([M+Na]⁺) 503.1787, found 503.1786.

Synthesis of tert-butyl 4-benzyl-4-(((2,4,5-trifluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-21). Compound 75-21 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2,4,5-trifluorobenzenesulfonyl chloride (0.73 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-21. White solid, 1.13 g (86%). m.p. 134.9–135.6 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.15 (t, J = 5.8 Hz, 1H), 7.91–7.82 (m, 2H), 7.25–7.11 (m, 5H), 3.43–3.39 (m, 2H), 3.21–3.17 (m, 2H), 2.78 (d, J = 5.5 Hz, 2H), 2.65 (s, 2H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.24–1.19 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 155.23 (dd, J = 2.9 Hz and 10.1 Hz), 154.49, 154.15 (dd, J = 2.9 Hz and 10.2 Hz), 153.55 (dd, J = 2.9 Hz and 10.2 Hz), 136.53, 130.30, 128.54, 126.93, 124.37 (dt, J = 4.2 Hz and 16.2 Hz), 119.04 (dt, J = 1.6 Hz and 20.9 Hz), 107.47 (dd, J = 21.7 Hz and 27.3 Hz), 79.72, 47.67, 42.47, 39.71, 38.88, 36.28, 32.27, 28.49; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −110.11 (dd, J = 8.0 and 16.5 Hz), −126.54 (dd, J = 8.2 and 22.4 Hz), −140.55 (dd, J = 15.8 and 22.4 Hz); ESI-HR-MS: (m/z) calcd. for C₂₄H₂₉F₃N₂NaO₄S ([M+Na]⁺) 521.1692, found 521.1697.

Synthesis of tert-butyl 4-benzyl-4-(((3-chloro-4-fluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-22). Compound 75-22 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3-chloro-4-fluorobenzenesulfonyl chloride (0.72 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-22. White solid, 1.13 g (87%). m.p 178.5–179.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.01 (dd, J = 2.3 Hz and 6.8 Hz, 1H), 7.85–7.82 (m, 1H), 7.77 (t, J = 6.5 Hz, 1H), 7.77 (t, J = 6.5 Hz, 1H), 7.23–7.15 (m, 3H), 7.11–7.09 (m, 2H), 3.44–3.39 (m, 2H), 3.19–3.16 (m, 2H), 2.66–2.62 (m, 4H), 1.35 (s, 9H), 1.31–1.29 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 161.54, 159.84, 154.96, 136.85 (d, J = 3.8 Hz), 136.59, 130.33, 130.06, 128.56, 127.59 (d, J = 8.5 Hz), 126.99, 122.65 (d, J = 18.7 Hz), 117.58 (d, J = 22.2 Hz), 79.79, 47.87, 42.54, 39.80, 38.95, 36.29, 32.39, 28.54; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −109.99; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₀ClFN₂NaO₄S ([M+Na]⁺) 519.1491, found 519.1495.

Synthesis of tert-butyl 4-benzyl-4-(((2,3,4-trifluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-23). Compound 75-23 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2,3,4-trifluorobenzenesulfonyl chloride (0.73 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-23. White solid, 1.12 g (85%). m.p. 151.7–152.6 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.19 (t, J = 6.3 Hz, 1H), 7.68–7.64 (m, 1H), 7.55–7.50 (m, 1H), 7.25–7.22 (m, 2H), 7.20–7.17 (m, 1H), 7.14–7.13 (m, 2H), 3.43–3.38 (m, 2H), 3.22–3.17 (m, 2H), 2.78 (d, J = 6.0 Hz, 2H), 2.66 (s, 2H), 1.35 (s, 9H), 1.34–1.31 (m, 2H), 1.24–1.19 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.93, 154.48 (ddd, J = 3.0, 10.2 and 259.3 Hz), 148.45 (ddd, J = 3.8, 11.5 and 258.0 Hz), 140.41 (dt, J = 15.3 and 257.4 Hz), 136.55, 130.25, 128.64, 127.05, 125.62 (d, J = 9.8 Hz), 124.60 (q, J = 3.2 Hz), 112.71 (dd, J = 3.6 and 18.1 Hz), 79.76, 47.70, 42.73, 39.76, 38.89, 36.37, 32.39, 28.53; ¹⁹F NMR (471 MHz, CDCl₃) δ −124.18 (dd, J = 13.0 and 20.0 Hz), −131.04 (dd, J = 13.0 and 21.4 Hz), −156.25 (t, J = 21.0 Hz); ESI-HR-MS: (m/z) calcd. for C₂₄H₂₉F₃N₂NaO₄S ([M+Na]⁺) 521.1692, found 521.1700.

Synthesis of tert-butyl 4-benzyl-4-(((3,5-bis(trifluoromethyl)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-24). Compound 75-24 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3,5-bis(trifluoromethyl)benzenesulfonyl chloride (0.99 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-24. White solid, 1.31 g (86%). m.p. 178.6–179.7 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.50 (s, 1H), 8.42–8.41 (m, 2H), 8.02 (t, J = 6.0 Hz, 1H), 7.20–7.15 (m, 3H), 7.10–7.08 (m, 2H), 3.43–3.38 (m, 2H), 3.23–3.17 (m, 2H), 2.71 (d, J = 6.0 Hz, 2H), 2.64 (s, 2H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.24–1.18 (m, 2H); ¹³C NMR (151 MHz, CD₃OD) δ 156.60, 145.17, 138.11, 133.92 (q, J = 34.2 Hz), 131.73, 129.03, 128.56, 128.54, 127.50, 127.22 (t, J = 3.7 Hz), 124.17 (q, J = 272.7 Hz), 81.03, 42.36, 41.05, 40.12, 37.17, 32.54, 28.65; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −61.49; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₀F₆N₂NaO₄S ([M+Na]⁺) 603.1723, found 603.1724.

Synthesis of tert-butyl 4-benzyl-4-(((2-chloro-4-fluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-25). Compound 75-25 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2-chloro-4-fluorobenzenesulfonyl chloride (0.72 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-25. White solid, 1.18 g (90%). m.p. 204.4–206.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.01 (dd, J = 6.0 Hz and 9.0 Hz,1H), 7.97 (t, J = 6.3 Hz, 1H), 7.71 (dd, J = 2.5 Hz and 8.5 Hz,1H), 7.43–7.39 (m, 1H), 7.25–7.22 (m, 2H), 7.19–7.18 (m, 1H), 7.14–7.12 (m, 2H), 3.43–3.38 (m, 2H), 3.18–3.12 (m, 2H), 2.76 (d, J = 6.5 Hz, 2H), 2.65 (s, 2H), 1.34 (s, 9H), 1.32–1.30 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 165.69 (d, J = 258.7 Hz), 154.87, 136.63, 133.51 (d, J = 9.7 Hz), 133.28 (d, J = 3.62 Hz), 132.99 (d, J = 11.0 Hz), 130.37, 128.53, 126.87, 119.29 (d, J = 25.5 Hz), 114.74 (d, J = 21.4 Hz), 79.65, 47.43, 42.56, 39.71, 38.87, 36.32, 32.41, 28.50; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −105.21; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₀ClFN₂NaO₄S ([M+Na]⁺) 519.1491, found 519.1499.

Synthesis of tert-butyl 4-benzyl-4-(((3-cyano-4-fluorophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-26). Compound 75-26 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3-cyano-4-fluorobenzenesulfonyl chloride (0.69 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-26. White solid, 0.74 g (58%). m.p. 207.8–209.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.36 (dd, J = 2.5 Hz and 6.0 Hz,1H), 8.21–8.18 (m, 1H), 7.85–7.77 (m, 2H), 7.24–7.17 (m, 3H), 7.12–7.11 (m, 2H), 3.45–3.40 (m, 2H), 3.20–3.18 (m, 2H), 2.69 (d, J = 6.5 Hz, 2H), 2.62 (s, 2H), 1.35 (s, 9H), 1.31–1.29 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 165.13 (d, J = 9.5 Hz), 154.97, 137.60, 137.58, 136.58, 133.98, 133.91, 133.03, 130.23, 128.77, 127.26, 117.84 (d, J = 20.7 Hz), 112.35, 103.12 (d, J = 16.6 Hz), 79.93, 48.28, 42.77, 39.78, 38.97, 36.44, 32.51, 28.56; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −102.49; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₀FN₃NaO₄S ([M+Na]⁺) 510.1833, found 510.1839.

Synthesis of tert-butyl 4-benzyl-4-(((4-(tert-butyl)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-27). Compound 75-27 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-tert-butylbenzenesulfonyl chloride (0.73 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-27. White solid, 1.10 g (84%) m.p. 190.0–190.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.76–7.73 (m, 2H), 7.63–7.60 (m, 2H), 7.57 (t, J = 6.3 Hz, 1H), 7.19–7.13 (m, 3H), 7.08–7.06 (m, 2H), 3.43–3.38 (m, 2H), 3.12–3.06 (m, 2H), 2.62–2.61 (m, 4H), 1.35 (s, 9H), 1.31 (s, 9H), 1.29–1.27 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 156.66, 154.93, 136.70, 136.55, 130.44, 128.36, 127.03, 126.66, 126.29, 79.59, 47.22, 42.45, 39.76, 38.91, 36.18, 35.27, 32.38, 31.19, 28.52; ESI-HR-MS: (m/z) calcd. for C₂₈H₄₁N₂O₄S ([M+H]⁺) 501.2782, found 501.2790.

Synthesis of tert-butyl 4-benzyl-4-(((4-(trifluoromethyl)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-28). Compound 75-28 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-(trifluoromethyl)benzenesulfonyl chloride (0.77 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-28. White solid, 1.20 g (89%). m.p. 131.2–132.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.05–8.00 (m, 4H), 7.89 (t, J = 5.5 Hz, 1H), 7.20–7.14 (m, 3H), 7.08–7.06 (m, 2H), 3.44–3.39 (m, 2H), 3.18–3.13 (m, 2H), 2.67–2.63 (m, 4H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.24–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.95, 143.31, 136.54, 134.63 (q, J = 33.1 Hz), 130.30, 128.55, 127.65, 126.97, 126.51 (q, J = 5.6 Hz), 123.30 (q, J = 273.1 Hz), 79.79, 47.83, 42.48, 39.77, 38.96, 36.31, 32.38, 28.52; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −61.57; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₁F₃N₂NaO₄S ([M+Na]⁺) 535.1849, found 535.1851.

Synthesis of tert-butyl 4-benzyl-4-(((4-fluoro-3-(trifluoromethyl)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-29). Compound 75-29 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-fluoro-3-(trifluoromethyl)benzenesulfonyl chloride (0.83 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-29. White solid, 0.96 g (69%). m.p. 196.2–197.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.21–8.16 (m, 2H), 7.86 (t, J = 6.3 Hz, 1H), 7.81–7.77 (m, 1H), 7.21–7.17 (m, 3H), 7.10–7.08 (m, 2H), 3.43–3.38 (m, 2H), 3.20–3.15 (m, 2H), 2.66–2.63 (m, 4H), 1.35 (s, 9H), 1.31–1.29 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 161.70 (d, J = 264.1 Hz), 155.15, 136.93 (d, J = 3.9 Hz), 136.44, 133.10 (d, J = 9.8 Hz), 130.33, 128.05, 126.62, 126.49, 122.00 (q, J = 237.8 Hz), 119.56–118.88 (m), 117.99 (d, J = 27.4 Hz), 77.94, 47.49, 41.49, 39.69, 38.73, 35.89, 31.57, 28.14; ¹⁹F NMR (471 MHz, CD₃OD) δ −59.72 (d, J = 11.8 Hz), −108.93 (q, J = 12.2 Hz); ESI-HR-MS: (m/z) calcd. for C₂₅H₃₀F₄N₂NaO₄S ([M+Na]⁺) 553.1755, found 553.1755.

Synthesis of tert-butyl 4-benzyl-4-(((4-(trifluoromethoxy)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-30). Compound 75-30 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-(trifluoromethoxy)benzenesulfonyl chloride (0.82 g, 3.16 mmol) and Et₃N (0.80 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-30. White solid, 1.20 g (86%). m.p. 149.8–150.7 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.97–7.95 (m, 2H), 7.78 (t, J = 6.0 Hz, 1H), 7.61 (d, J = 8.5 Hz, 2H), 7.20–7.14 (m, 3H), 7.09–7.07 (m, 2H), 3.44–3.39 (m, 2H), 3.17–3.12 (m, 2H), 2.66–2.63 (m, 4H), 1.35 (s, 9H), 1.31–1.29 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.94, 152.26 (q, J = 1.9 Hz), 138.08, 136.55, 130.34, 129.28, 128.44, 126.84, 121.17, 120.33 (q, J = 259.6 Hz), 79.71, 47.62, 42.32, 39.77, 38.88, 36.23, 32.31, 28.49; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −56.77; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₁F₃N₂NaO₅S ([M+Na]⁺) 551.1798, found 551.1804.

Synthesis of tert-butyl 4-benzyl-4-(((4-fluoro-2-(trifluoromethyl)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-31). Compound 75-31 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-fluoro-2-(trifluoromethyl)benzenesulfonyl chloride (0.82 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-31. White solid, 1.22 g (87%). m.p. 187.5–188.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.16–8.11 (m, 2H), 7.91 (dd, J = 2.8 Hz and 9.3 Hz, 1H), 7.82–7.78 (m, 1H), 7.27–7.24 (m, 2H), 7.21–7.17 (m, 1H), 7.15–7.13 (m, 2H), 3.43–3.39 (m, 2H), 3.21–2.18 (m, 2H), 2.81 (d, J = 6.0 Hz, 2H), 2.66 (s, 2H), 1.38–1.35 (m, 2H), 1.35 (s, 9H), 1.24–1.19 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 165.19, 163.48, 154.94, 136.59, 134.97 (d, J = 8.8 Hz), 134.59 (d, J = 3.9 Hz), 130.23, 128.63, 126.99, 122.22 (qd, J = 2.1 and 274.3 Hz), 119.11 (d, J = 20.8 Hz), 116.94 (dq, J = 6.4 and 26.1 Hz), 79.76, 47.87, 42.45, 39.75, 38.90, 36.47, 32.45, 28.54; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −56.52, −105.12; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₀F₄N₂NaO₄S ([M+Na]⁺) 553.1755, found 553.1754.

Synthesis of tert-butyl 4-benzyl-4-((naphthalene-2-sulfonamido)methyl)piperidine-1-carboxylate (75-32). Compound 75-32 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using naphthalene-2-sulfonyl chloride (0.72 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-32. White solid, 1.12 g (86%). m.p. 134.1–134.8 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.44 (s, 1H), 8.16 (d, J = 8.5 Hz, 2H), 8.06 (d, J = 8.0 Hz, 1H), 7.88 (dd, J = 2.0 Hz and 3.5 Hz, 1H), 7.74–7.66 (m, 3H), 7.11–7.05 (m, 5H), 3.42–3.37 (m, 2H), 3.17–3.12 (m, 2H), 2.51–2.79 (m, 4H), 1.33 (s, 9H), 1.31–1.29 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.92, 136.64, 136.39, 134.94, 132.24, 130.39, 129.77, 129.34, 129.02, 128.59, 128.35, 128.04, 127.78, 126.70, 122.24, 79.60, 47.43, 42.44, 39.79, 38.90, 36.18, 32.36, 28.50; ESI-HR-MS: (m/z) calcd. for C₂₈H₃₅N₂O₄S ([M+H]⁺) 495.2312, found 495.2308.

Synthesis of tert-butyl 4-benzyl-4-((naphthalene-1-sulfonamido)methyl)piperidine-1-carboxylate (75-33). Compound 75-33 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using naphthalene-1-sulfonyl chloride (0.72 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-33. White solid, 1.03 g (79%). m.p. 149.9–151.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.80 (d, J = 8.5 Hz, 1H), 8.23 (d, J = 8.0 Hz, 1H), 8.12–8.09 (m, 2H), 7.96 (t, J = 6.3 Hz, 1H), 7.78–7.74 (m, 1H), 7.72–7.68 (m, 1H), 7.65–7.62 (m, 1H), 7.11–7.04 (m, 3H), 6.97–6.95 (m, 2H), 3.36–3.31 (m, 2H), 3.00 (s, 2H), 2.63 (d, J = 6.0 Hz, 2H), 2.58 (s, 2H), 1.33 (s, 9H), 1.27–1.22 (m, 2H), 1.17–1.11 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.84, 136.57, 134.49, 134.37, 134.29, 130.26, 129.87, 129.34, 128.62, 128.32, 128.15, 127.10, 126.63, 124.29, 124.27, 79.53, 47.07, 42.84, 39.68, 38.88, 36.13, 32.37, 28.49; ESI-HR-MS: (m/z) calcd. for C₂₈H₃₅N₂O₄S ([M+H]⁺) 495.2312, found 495.2300.

Synthesis of tert-butyl 4-benzyl-4-(((4-cyclohexylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-34). Compound 75-34 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-cyclohexylbenzenesulfonyl chloride (0.82 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-34. White solid, 1.16 g (84%). m.p. 169.4–170.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.72 (d, J = 8.5 Hz, 2H), 7.55 (t, J = 6.5 Hz, 1H), 7.45 (d, J = 8.0 Hz, 2H), 7.20–7.13 (m, 3H), 7.08–7.06 (m, 2H), 3.43–3.38 (m, 2H), 3.12–3.06 (m, 2H), 2.61–2.58 (m, 5H), 1.81–1.78 (m, 4H), 1.73–1.70 (m, 1H), 1.47–1.37 (m, 4H), 1.35 (s, 9H), 1.32–1.28 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.93, 153.54, 136.84, 136.70, 130.43, 128.40, 127.78, 127.26, 126.70, 79.60, 47.26, 44.66, 42.54, 39.77, 38.93, 36.20, 34.22, 32.41, 28.53, 26.76, 26.06; ESI-HR-MS: (m/z) calcd. for C₃₀H₄₂N₂O₄S ([M+H]⁺) 549.2763, found 549.2758.

Synthesis of tert-butyl 4-benzyl-4-(((3-(methylsulfonyl)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-35). Compound 75-35 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3-(methylsulfonyl)benzenesulfonyl chloride (0.80 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-35. White solid, 1.04 g (76%). m.p. 155.3–156.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.33–8.32 (m, 1H), 8.24–8.22 (m, 1H), 8.16–8.14 (m, 1H), 7.93–7.88 (m, 2H), 7.22–7.16 (m, 3H), 7.09–7.08 (m, 2H), 3.43–3.38 (m, 2H), 3.32 (s, 3H), 3.18 (br, 2H), 2.68–2.63 (m, 4H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.94, 142.19, 141.85, 136.55, 132.04, 131.33, 130.67, 130.37, 128.54, 126.93, 126.28, 79.75, 47.89, 44.46, 42.41, 39.76, 38.91, 36.29, 32.22, 28.52; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₄N₂NaO₆S₂ ([M+Na]⁺) 545.1750, found 545.1750.

Synthesis of tert-butyl 4-benzyl-4-(((4-propylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-36). Compound 75-36 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-n-propylbenzenesulfonyl chloride (0.69 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-36. White solid, 1.13 g (88%). m.p. 161.5–162.7 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.72 (d, J = 8.0 Hz, 2H), 7.55 (t, J = 6.5 Hz, 1H), 7.41 (d, J = 8.0 Hz, 2H), 7.20–7.14 (m, 3H), 7.09–7.07 (m, 2H), 3.43–3.38 (m, 2H), 3.14–3.09 (m, 2H), 2.66–2.60 (m, 6H), 1.66–1.58 (m, 2H), 1.35 (s, 9H), 1.32–1.28 (m, 2H), 1.21–1.16 (m, 2H), 0.893 (t, J = 7.3 Hz, 3H); ¹³C NMR (151 MHz, CDCl₃) δ 154.94, 148.36, 136.82, 136.71, 130.42, 129.34, 128.41, 127.19, 126.73, 79.62, 47.32, 42.55, 39.79, 38.93, 37.96, 36.20, 32.41, 28.53, 24.29, 13.83; ESI-HR-MS: (m/z) calcd. for C₂₇H₃₈N₂NaO₄S ([M+Na]⁺) 509.2444, found 509.2444.

Synthesis of tert-butyl 4-benzyl-4-(((2,4,6-triisopropylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-37). Compound 75-37 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2,4,6-triisopropylbenzenesulfonyl chloride (0.96 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-37. White solid, 1.16 g (77%). m.p. 129.5–130.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.51 (t, J = 6.5 Hz, 1H), 7.22 (s, 2H), 7.20–7.14 (m, 3H), 7.08–7.06 (m, 2H), 4.18–4.13 (m, 2H), 3.37–3.33 (m, 2H), 3.14–3.09 (m, 2H), 2.94–2.88 (m, 1H), 2.70 (d, J = 6.0 Hz, 2H), 2.63 (s, 2H), 1.34 (s, 9H), 1.31–1.29 (m, 2H), 1.20–1.16 (m, 20H); ¹³C NMR (151 MHz, CDCl₃) δ 154.89, 152.99, 150.29, 136.77, 132.24, 130.36, 128.45, 126.71, 123.99, 79.62, 46.99, 42.29, 39.81, 38.96, 36.30, 34.22, 32.34, 29.87, 28.50, 25.09, 23.65; ESI-HR-MS: (m/z) calcd. for C₃₃H₅₀N₂NaO₄S ([M+Na]⁺) 593.3383, found 593.3381.

Synthesis of tert-butyl 4-(([1,1′-biphenyl]-4-sulfonamido)methyl)-4-benzylpiperidine-1-carboxylate (75-38). Compound 75-38 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using [1,1′-biphenyl]-4-sulfonyl chloride (0.80 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-38. White solid, 1.23 g (90%). m.p. 146.3–147.9 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.92–7.88 (m, 4H), 7.76–7.75 (m, 2H), 7.69 (t, J = 6.5 Hz, 1H), 7.54–7.51 (m, 2H), 7.47–7.43 (m, 1H), 7.20–7.13 (m, 3H), 7.10–7.08 (m, 2H), 3.44–3.39 (m, 2H), 3.18–3.14 (m, 2H), 2.67–2.64 (m, 4H), 1.34 (s, 9H), 1.32–1.31 (m, 2H), 1.24–1.19 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.93, 145.82, 139.28, 138.16, 136.66, 130.42, 129.18, 128.64, 128.39, 127.92, 127.66, 127.41, 126.72, 79.61, 47.41, 42.40, 39.79, 38.95, 36.21, 32.38, 28.51; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₆N₂NaO₄S₂ ([M+Na]⁺) 543.2288, found 543.2289.

Synthesis of tert-butyl 4-benzyl-4-(((4-methylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-39). Compound 75-39 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-toluenesulfonyl chloride (0.60 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-39. White solid, 1.04 g (86%). m.p. 172.5–173.7 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.70 (d, J = 8.0 Hz, 2H), 7.54 (t, J = 6.3 Hz, 1H), 7.40 (d, J = 8.0 Hz, 2H), 7.21–7.15 (m, 3H), 7.09–7.07 (m, 2H), 3.43–3.38 (m, 2H), 3.14 (s, 2H), 2.62–2.58 (m, 4H), 2.39 (s, 3H), 1.35 (s, 9H), 1.32–1.28 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.92, 143.66, 136.69, 136.62, 130.44, 129.90, 128.33, 127.15, 126.65, 79.56, 47.26, 42.39, 39.77, 38.89, 36.12, 32.34, 28.50, 21.62; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₄N₂NaO₄S ([M+Na]⁺) 481.2131, found 481.2128.

Synthesis of tert-butyl 4-benzyl-4-(((4-ethylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-40). Compound 75-40 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-ethylbenzenesulfonyl chloride (0.65 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-40. White solid, 1.07 g (86%). m.p 166.2–167.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.73 (d, J = 8.0 Hz, 2H), 7.55 (t, J = 6.5 Hz, 1H), 7.44 (d, J = 8.0 Hz, 2H), 7.20–7.14 (m, 3H), 7.09–7.07 (m, 2H), 3.43–3.38 (m, 2H), 3.15–3.10 (m, 2H), 2.72–2.67 (m, 2H), 2.62–2.60 (m, 4H), 1.35 (s, 9H), 1.33–1.28 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.94, 149.80, 136.79, 136.69, 130.43, 128.76, 128.35, 127.26, 126.67, 79.61, 47.26, 42.42, 39.78, 38.90, 36.15, 32.36, 28.90, 28.51, 15.23; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₆N₂NaO₄S ([M+Na]⁺) 495.2288, found 495.2284.

Synthesis of tert-butyl 4-benzyl-4-(((4-isopropylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-41). Compound 75-41 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-isopropylbenzenesulfonyl chloride (0.69 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-41. White solid, 1.04 g (81%). m.p. 186.0–186.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.75–7.72 (m, 2H), 7.56 (t, J = 6.3 Hz, 1H), 7.48–7.46 (m, 2H), 7.20–7.13 (m, 3H), 7.08–7.06 (m, 2H), 3.43–3.38 (m, 2H), 3.13–3.08 (m, 2H), 3.01–2.96 (m, 1H), 2.62–2.60 (m, 4H), 1.35 (s, 9H), 1.32–1.28 (m, 2H), 1.23 (d, J = 7.0 Hz, 6H), 1.20–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.91, 154.36, 136.90, 136.69, 130.44, 128.33, 127.38, 127.30, 126.64, 79.56, 47.20, 42.40, 39.77, 38.89, 36.16, 34.26, 32.36, 28.51, 23.75; ESI-HR-MS: (m/z) calcd. for C₂₇H₃₈N₂NaO₄S ([M+Na]⁺) 509.2444, found 509.2442.

Synthesis of tert-butyl 4-benzyl-4-(((3-isopropylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-42). Compound 75-42 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 3-isopropylbenzenesulfonyl chloride (0.69 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-42. White solid, 1.01 g (79%). m.p. 158.2–160.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.69 (s, 1H), 7.63–7.61 (m, 1H), 7.58 (t, J = 6.3 Hz, 1H), 7.55–7.51 (m, 2H), 7.20–7.16 (m, 3H), 7.08–7.06 (m, 2H), 3.41–3.36 (m, 2H), 3.14–3.10 (m, 2H), 3.03–2.97 (m, 1H), 2.62–2.60 (m, 4H), 1.35 (s, 9H), 1.32–1.28 (m, 2H), 1.23 (d, J = 7.0 Hz, 6H), 1.20–1.16 (m, 2H); ¹³C NMR (201 MHz, CDCl₃) δ 154.91, 150.50, 139.50, 136.64, 131.14, 130.40, 129.30, 128.35, 126.67, 124.99, 124.58, 79.58, 47.20, 42.42, 39.83, 38.87, 36.13, 34.19, 32.35, 28.50, 23.87; ESI-HR-MS: (m/z) calcd. for C₂₇H₃₈N₂NaO₄S ([M+Na]⁺) 509.2444, found 509.2444.

Synthesis of tert-butyl 4-benzyl-4-(((2-methylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-43). Compound 75-43 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 2-methylbenzenesulfonyl chloride (0.60 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-43. White solid, 1.07 g (89%). m.p. 174.2–175.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.79–7.77 (m, 1H), 7.73–7.69 (m, 1H), 7.53–7.50 (m, 1H), 7.42–7.36 (m, 2H), 7.24–7.15 (m, 3H), 7.10–7.07 (m, 2H), 3.40–3.32 (m, 2H), 3.14 (s, 2H), 2.69–2.68 (m, 1H), 2.63–2.58 (m, 5H), 2.39 (s, 1H), 1.34 (s, 9H), 1.30–1.28 (m, 2H), 1.20–1.15 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 154.93, 137.66, 136.90, 136.82, 133.02, 132.76, 130.31, 129.59, 128.58, 126.89, 126.43, 79.68, 47.36, 42.91, 39.79, 38.91, 36.36, 32.48, 28.54, 20.44; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₄N₂NaO₄S ([M+Na]⁺) 481.2131, found 481.2128.

Synthesis of tert-butyl 4-benzyl-4-(((4-hydroxyphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-44). Compound 75-44 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-hydroxybenzenesulfonyl chloride (0.61 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-44. White solid, 1.06 g (88%). m.p. 200.0–203.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 10.36 (s, 1H), 7.64–7.62 (m, 2H), 7.36 (t, J = 6.5 Hz, 1H), 7.21–7.14 (m, 3H), 7.08–7.06 (m, 2H), 6.92–6.90 (m, 2H), 3.43–3.38 (m, 2H), 3.17–3.13 (m, 2H), 2.61–2.56 (m, 4H), 1.35 (s, 9H), 1.32–1.28 (m, 2H), 1.21–1.16 (m, 2H); ¹³C NMR (151 MHz, CDCl₃ + CD₃OD) δ 161.04, 155.06, 136.46, 130.22, 129.60, 128.88, 127.79, 126.12, 115.43, 79.73, 46.84, 41.62, 39.59, 38.61, 35.59, 31.53, 27.88; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₂N₂NaO₅S ([M+Na]⁺) 483.1924, found 483.1920.

Synthesis of tert-butyl 4-benzyl-4-(((4-carbamoylphenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-45). Compound 75-45 was prepared according to General Procedure 1 from 73 (0.80 g, 2.63 mmol) using 4-carbamoylbenzenesulfonyl chloride (0.69 g, 3.16 mmol) and Et₃N (0.83 g, 7.89 mmol) in dried CH₂Cl₂ (8 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-45. White solid, 1.06 g (83%). m.p. 157.5–158.6 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.17 (s, 1H), 8.06–8.04 (m, 2H), 7.89–7.87 (m, 2H), 7.74 (t, J = 6.5 Hz, 1H), 7.61 (s, 1H), 7.21–7.14 (m, 3H), 7.09–7.07 (m, 2H), 3.43–3.39 (m, 2H), 3.19–3.15 (m, 2H), 2.65–2.62 (m, 4H), 1.35 (s, 9H), 1.32–1.29 (m, 2H), 1.23–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 168.39, 155.03, 142.89, 137.43, 136.64, 130.47, 128.54, 128.42, 127.28, 126.81, 79.82, 47.72, 42.22, 39.83, 38.94, 36.22, 32.13, 28.53; ESI-HR-MS: (m/z) calcd. for C₂₅H₃₃N₃NaO₅S ([M+Na]⁺) 510.2033, found 510.2032.

Synthesis of tert-butyl 4-benzyl-4-(((4-(methoxycarbonyl)phenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-46). Compound 75-46 was prepared according to General Procedure 1 from 73 (1.50 g, 4.93 mmol) using methyl 4-(chlorosulfonyl)benzoate (1.39 g, 5.92 mmol) and Et₃N (1.50 g, 14.8 mmol) in dried CH₂Cl₂ (15 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-46. White solid, 2.06 g (83%). m.p. 174.0–175.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.17–8.14 (m, 2H), 7.97–7.95 (m, 2H), 7.84 (t, J = 6.5 Hz, 1H), 7.21–7.14 (m, 3H), 7.10–7.08 (m, 2H), 3.90 (s, 3H), 3.42–3.38 (m, 2H), 3.18–3.13 (m, 2H), 2.67–2.62 (m, 4H), 1.34 (s, 9H), 1.31–1.28 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 165.67, 154.92, 143.63, 136.57, 134.06, 130.52, 130.33, 128.51, 127.12, 126.90, 79.71, 52.80, 47.73, 42.53, 39.77, 38.92, 36.27, 32.34, 28.51; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₄N₂NaO₆S ([M+Na]⁺) 525.2030, found 525.2027.

Synthesis of tert-butyl 4-benzyl-4-(((3-nitrophenyl)sulfonamido)methyl)piperidine-1-carboxylate (75-47). Compound 75-47 was prepared according to General Procedure 1 from 73 (2.00 g, 6.57 mmol) using methyl 3-nitrobenzenesulfonyl chloride (1.75 g, 7.88 mmol) and Et₃N (2.00 g, 19.7 mmol) in dried CH₂Cl₂ (20 mL). Purification by column chromatography (EtOAc/PE = 1/3, by v/v) gave 75-47. White solid, 2.67 g (83%). m.p. 20.1–208.4 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.57 (t, J = 2.0 Hz, 1H)), 8.51–8.48 (m, 1H), 8.25–8.23 (m, 1H), 7.96–7.91 (m, 2H), 7.22–7.15 (m, 3H), 7.12–7.10 (m, 2H), 3.43–3.38 (m, 2H), 3.21–3.16 (m, 2H), 2.67–2.63 (m, 4H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 155.04, 148.12, 142.26, 136.30, 132.25, 130.40, 130.22, 127.79, 126.66, 126.21, 121.73, 79.77, 47.33, 41.25, 39.53, 38.58, 35.72, 31.28, 27.83; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₁N₃NaO₆S ([M+Na]⁺) 512.1826, found 512.1827.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)methanesulfonamide (C-4-1). Following General Procedure 3, 75-1 (0.30 g, 0.784 mmol) was first treated with TFA (1.5 mL) in CH₂Cl₂ (0.9 mL), and the intermediate obtained was reacted with 7·TFA (0.28 g, 0.941 mmol) using EDCI (0.38 g, 1.96 mmol), HOBT (8 mg, 0.059 mmol), and DIPEA (0.61 g, 4.70 mmol) in dried THF (3 mL). Purification by column chromatography (EtOAc) gave C-1-1. White solid, 0.26 g (71%). m.p. 112.1–114.5 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.57 (t, J = 2.0 Hz, 1H)), 8.51–8.48 (m, 1H), 8.25–8.23 (m, 1H), 7.96–7.91 (m, 2H), 7.22–7.15 (m, 3H), 7.12–7.10 (m, 2H), 3.43–3.38 (m, 2H), 3.21–3.16 (m, 2H), 2.67–2.63 (m, 4H), 1.35 (s, 9H), 1.32–1.30 (m, 2H), 1.23–1.18 (m, 2H); ¹³C NMR (151 MHz, CDCl₃) δ 155.04, 148.12, 142.26, 136.30, 132.25, 130.40, 130.22, 127.79, 126.66, 126.21, 121.73, 79.77, 47.33, 41.25, 39.53, 38.58, 35.72, 31.28, 27.83; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₉N₄O₃S ([M+H]⁺) 465.1955 found 465.1953.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-1,1,1-trifluoromethanesulfonamide (C-4-2). Following General Procedure 3, 75-2 (0.65 g, 1.49 mmol) was first treated with TFA (3.3 mL) in CH₂Cl₂ (2 mL), and the intermediate obtained was reacted with 7·TFA (0.53 g, 1.79 mmol) using EDCI (0.72 g, 3.73 mmol), HOBT (15 mg, 0.112 mmol), and DIPEA (1.16 g, 8.94 mmol) in dried THF (6.5 mL). Purification by column chromatography (EtOAc) gave C-4-2. White solid, 0.33 g (43%). m.p. 116.2–118.3 °C. ¹H NMR (500 MHz, CDCl₃) δ 8.77–8.76 (m, 1H)), 8.68–8.64 (m, 2H), 7.72–7.64 (m, 3H), 7.42–7.39 (m, 1H), 7.27–7.25 (m, 3H), 7.01–6.93 (m, 2H), 3.95–3.92 (m, 0.50H), 3.76–3.62 (m, 1H), 3.46–3.39 (m, 0.73H), 3.15–2.81 (m, 4H), 2.62 (s, 1H), 2.42–2.32 (m, 1H), 1.53–1.43 (m, 1H), 1.34–1.09 (m, 2H), 0.71–0.50 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.74, 167.62, 151.99, 151.80, 150.67, 149.96, 146.61, 146.56, 136.24, 136.10, 135.85, 135.63, 131.30, 130.33, 130.12, 128.72, 128.67, 127.27, 127.16, 123.73, 123.48, 123.38, 121.26, 118.69, 50.71, 49.72, 47.91, 43.00, 42.66, 41.06, 37.49, 36.29, 36.19, 31.65, 31.29, 30.98, 30.62; ESI-HR-MS: (m/z) calcd. for C₂₅H₂₆F₃N₄O₃S ([M+H]⁺) 519.1673, found 519.1667.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)ethanesulfonamide (C-4-3). Following General Procedure 3, 75-3 (0.75 g, 1.89 mmol) was first treated with TFA (3.8 mL) in CH₂Cl₂ (2.3 mL), and the intermediate obtained was reacted with 7·TFA (0.68 g, 2.27 mmol) using EDCI (0.91 g, 4.73 mmol), HOBT (19 mg, 0.142 mmol), and DIPEA (1.46 g, 11.3 mmol) in dried THF (7.5 mL). Purification by column chromatography (EtOAc) gave C-4-3. White solid, 0.75 g (82%). m.p. 104.6–106.2 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.78 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.68–8.64 (m, 2H), 7.84–7.79 (m, 1H), 7.59–7.54 (m, 3H), 7.28–7.20 (m, 4H), 7.11–7.03 (m, 2H), 3.92–3.70 (m, 1H), 3.48–3.46 (m, 0.43H), 3.34–3.33 (m, 1H), 3.18–3.07 (m, 1H), 3.02–2.97 (m, 3H), 2.87–2.76 (m, 1H), 2.64 (s, 1.65H), 2.47–2.34 (m, 1H), 1.51–1.34 (m, 1.54H), 1.20 (t, J = 7.3 Hz, 3H), 1.16–1.10 (m, 1.41H), 0.88–0.51 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.62, 167.56, 152.08, 151.92, 150.57, 150.31, 150.21, 146.38, 136.27, 136.16, 136.10, 131.54, 130.30, 130.05, 128.68, 128.60, 127.15, 127.02, 123.64, 123.43, 123.31, 47.95, 46.78, 46.60, 46.10, 43.81, 42.76, 42.69, 41.25, 37.57, 37.47, 36.39, 31.94, 31.75, 31.59, 31.30; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₁N₄O₃S ([M+H]⁺) 479.2112, found 479.2109.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)cyclopropanesulfonamide (C-4-4). Following General Procedure 3, 75-4 (0.55 g, 1.35 mmol) was first treated with TFA (2.76 mL) in CH₂Cl₂ (1.7 mL), and the intermediate obtained was reacted with 7·TFA (0.48 g, 1.62 mmol) using EDCI (0.65 g, 3.38 mmol), HOBT (14 mg, 0.101 mmol), and DIPEA (1.05 g, 8.10 mmol) in dried THF (5.5 mL). Purification by column chromatography (EtOAc) gave C-4-4. White solid, 0.45 g (68%). m.p. 134.5–137.1 °C. ¹H NMR (500 MHz, CD₃OD) δ 8.78–8.77 (m, 1H), 8.68–8.60 (m, 2H), 7.88–7.84 (m, 1H), 7.69–7.68 (m, 2H), 7.59–7.56 (m, 1H), 7.30–7.08 (m, 5H), 4.59 (m, 0.51H), 4.01–3.80 (m, 1H), 3.60–3.41 (m, 1H), 3.22–3.17 (m, 1H), 3.07–2.98 (m, 2H), 2.86–2.79 (m, 1H), 2.69 (s, 1H), 2.55–2.44 (m, 2H), 1.60–1.23 (m, 3H), 1.04–0.97 (m, 4H), 0.70 (m, 0.55H); ¹³C NMR (126 MHz, CD₃OD) δ 169.08, 151.65, 150.57, 148.32, 137.95, 137.66, 132.94, 131.82, 129.18, 127.65, 125.28, 124.88, 47.43, 44.23, 43.52, 41.61, 38.82, 37.20, 32.65, 31.94, 30.31, 5.51, 5.47; ESI-HR-MS: (m/z) calcd. for C₂₇H₃₁N₄O₃S ([M+H]⁺) 491.2112, found 491.2110.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)thiophene-2-sulfonamide (C-4-5). Following General Procedure 3, 75-5 (0.82 g, 1.82 mmol) was first treated with TFA (4.1 mL) in CH₂Cl₂ (2.5 mL), and the intermediate obtained was reacted with 7·TFA (0.65 g, 2.18 mmol) using EDCI (0.87 g, 4.55 mmol), HOBT (19 mg, 0.137 mmol), and DIPEA (1.41 g, 10.9 mmol) in dried THF (8.2 mL). Purification by column chromatography (EtOAc) gave C-4-5. White foam, 0.51 g (53%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 4.5 Hz, 1H), 8.67–8.64 (m, 2H), 7.95–7.93 (m, 1H), 7.86–7.81 (m, 2H), 7.60–7.54 (m, 4H), 7.22–7.16 (m, 4H), 7.08–6.98 (m, 2H), 4.12–4.09 (m, 0.25H), 3.86–3.69 (m, 1H), 3.38–3.35 (m, 0.42H), 3.30–3.25 (m, 0.76H), 3.18–3.13 (m, 1H), 3.04–2.99 (m, 1H), 2.81–2.72 (m, 1H), 2.66–2.53 (m, 2H), 2.37–2.35 (m, 0.60H), 1.49–1.46 (m, 0.60H), 1.32–1.22 (m, 1H), 1.14–1.07 (m, 1.65H), 0.84–0.55 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.47, 167.37, 151.90, 151.70, 150.40, 149.97, 149.93, 146.26, 146.23, 140.60, 140.46, 136.12, 136.01, 135.99, 135.79, 132.18, 131.98, 131.91, 131.85, 131.33, 130.26, 130.08, 128.28, 127.52, 127.46, 126.74, 126.69, 123.51, 123.28, 123.08, 47.46, 46.27, 42.90, 42.66, 42.51, 41.51, 37.45, 37.39, 35.98, 35.84, 31.83, 31.54, 31.42, 31.19; ESI-HR-MS: (m/z) calcd. for C₂₈H₂₉N₄O₃S₂ ([M+H]⁺) 533.1676, found 533.1679.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)pyridine-3-sulfonamide (C-4-6). Following General Procedure 3, 75-6 (0.86 g, 1.93 mmol) was first treated with TFA (4.3 mL) in CH₂Cl₂ (2.6 mL), and the intermediate obtained was reacted with 7·TFA (0.69 g, 2.32 mmol) using EDCI (0.93 g, 4.83 mmol), HOBT (20 mg, 0.145 mmol), and DIPEA (1.50 g, 11.6 mmol) in dried THF (8.6 mL). Purification by column chromatography (EtOAc) gave C-4-6. White foam, 0.59 g (58%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.97–8.96 (m, 1H), 8.85–8.83 (m, 1H), 8.78–8.77 (m, 1H), 8.66–8.63 (m, 2H), 8.20–8.19 (m, 1H), 7.89–7.78 (m, 2H), 7.67–7.65 (m, 1H), 7.57–7.54 (m, 3H), 7.19–7.16 (m, 3H), 7.07–6.97 (m, 2H), 3.85–3.68 (m, 1H), 3.42–3.41 (m, 0.40H), 3.29–3.27 (m, 0.60H), 3.17–3.14 (m, 1H), 3.04–2.99 (m, 1H), 2.84–2.70 (m, 1H), 2.63–2.60 (m, 1.49H), 2.46–2.34 (m, 1.51H), 1.47–1.45 (m, 0.56H), 1.33–1.23 (m, 1H), 1.13–1.06 (m, 1.55H), 0.79–0.55 (m, 1H); ¹³C NMR (201 MHz, CDCl₃ + CD₃OD) δ 167.45, 167.34, 162.43, 162.25, 152.45, 151.58, 151.40, 150.26, 149.39, 149.29, 147.16, 146.40, 137.01, 136.10, 136.01, 135.85, 135.62, 134.91, 134.83, 131.14, 130.13, 130.00, 128.00, 126.52, 126.47, 123.98, 123.67, 123.24, 123.13, 116.96, 115.51, 47.15, 46.13, 42.66, 42.54, 42.03, 40.96, 37.41, 37.34, 35.84, 35.70, 31.31, 30.97, 30.79, 30.64; ESI-HR-MS: (m/z) calcd. for C₂₉H₃₀N₅O₃S ([M+H]⁺) 528.2064, found 528.2067.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-1-phenylmethanesulfonamide (C-4-7). Following General Procedure 3, 75-7 (0.63 g, 1.37 mmol) was first treated with TFA (3.2 mL) in CH₂Cl₂ (1.9 mL), and the intermediate obtained was reacted with 7·TFA (0.49 g, 1.64 mmol) using EDCI (0.66 g, 3.43 mmol), HOBT (14 mg, 0.103 mmol), and DIPEA (1.06 g, 8.22 mmol) in dried THF (6.3 mL). Purification by column chromatography (EtOAc) gave C-4-7. White foam, 0.49 g (66%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.78–8.77 (m, 1H), 8.71–8.65 (m, 2H), 7.84–7.79 (m, 1H), 7.60–7.54 (m, 3H), 7.40–7.36 (m, 5H), 7.29–7.10 (m, 5H), 7.03–7.01 (m, 1H), 4.35–4.34 (m, 2H), 4.13–3.87 (m, 1H), 3.73–3.38 (m, 1H), 3.31–3.25 (m, 0.61H), 3.18–3.14 (m, 1H), 3.05–3.01 (m, 0.60H), 2.96–2.89 (m, 1H), 2.79–2.68 (m, 1H), 2.58–2.55 (m, 1.58H), 2.43–2.27 (m, 1H), 1.45–1.42 (m, 0.51H), 1.30–1.29 (m, 0.69H), 1.10–1.03 (m, 1.57H), 0.91–0.45 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.29, 167.21, 151.76, 151.55, 150.29, 150.26, 149.83, 149.78, 146.16, 136.06, 136.03, 135.93, 135.81, 131.31, 131.26, 130.52, 130.45, 130.15, 129.96, 129.24, 129.13, 128.72, 128.68, 128.59, 128.19, 128.16, 126.64, 126.55, 123.44, 123.42, 123.20, 123.03, 58.57, 58.48, 47.77, 46.01, 43.03, 42.53, 42.43, 41.11, 37.31, 37.23, 36.17, 36.04, 31.41, 31.07, 30.87; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₃N₄O₃S ([M+H]⁺) 541.2268, found 541.2268.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)benzenesulfonamide (C-4-8). Following General Procedure 3, 75-8 (0.70 g, 1.57 mmol) was first treated with TFA (3.5 mL) in CH₂Cl₂ (2.1 mL), and the intermediate obtained was reacted with 7·TFA (0.56 g, 1.88 mmol) using EDCI (0.75 g, 3.93 mmol), HOBT (16 mg, 0.118 mmol), and DIPEA (1.22 g, 9.42 mmol) in dried THF (7 mL). Purification by column chromatography (EtOAc) gave C-4-8. White solid, 0.33 g (40%). m.p. 105–108 °C. ¹H NMR (500 MHz, CD₃OD) δ 8.76 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.67–8.58 (m, 2H), 7.86–7.81 (m, 3H), 7.67–7.53 (m, 6H), 7.19–7.17 (m, 3H), 7.05–6.93 (m, 2H), 7.03–7.01 (m, 1H), 3.98–3.78 (m, 1H), 3.44–3.33 (m, 1H), 3.19–3.16 (m, 0.49H), 3.11–2.98 (m, 1H), 2.88–2.72 (m, 1.59H), 2.63–2.38 (m, 3H), 1.53–1.50 (m, 0.59H), 1.44–1.28 (m, 1H), 1.25–0.98 (m, 2H), 0.65–0.60 (m, 0.54H); ¹³C NMR (126 MHz, CDCl₃) δ 167.55, 152.19, 151.94, 150.58, 150.32, 150.22, 146.38, 146.29, 139.61, 136.27, 136.15, 135.96, 132.96, 131.54, 131.46, 130.27, 130.03, 129.37, 128.55, 127.04, 126.94, 123.64, 123.59, 123.43, 123.20, 47.37, 46.11, 43.67, 42.78, 42.62, 41.96, 37.53, 37.46, 36.27, 36.12, 32.08, 31.83, 31.48; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₁N₄O₃S ([M+H]⁺) 527.2112, found 527.2109.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-4-fluorobenzenesulfonamide (C-4-9). Following General Procedure 3, 75-9 (0.90 g, 1.95 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.70 g, 2.34 mmol) using EDCI (0.94 g, 4.88 mmol), HOBT (20 mg, 0.146 mmol), and DIPEA (1.51 g, 11.7 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-9. White foam, 0.93 g (88%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.65–8.64 (m, 2H), 7.89–7.79 (m, 3H), 7.70–7.64 (m, 1H), 7.58–7.54 (m, 3H), 7.49–7.43 (m, 2H), 7.19–7.16 (m, 3H), 7.07–7.05 (m, 1H), 6.98–6.96 (m, 1H), 3.87–3.69 (m, 1H), 3.38 (m, 0.34H), 3.27–3.22 (m, 0.63H), 3.17–3.12 (m, 1H), 3.00–2.94 (m, 1H), 2.79 (m, 0.42H), 2.67–2.54 (m, 2H), 2.39–2.33 (m, 1.44H), 1.47–1.45 (m, 0.58H), 1.35–1.23 (m, 1H), 1.13–1.04 (m, 1.68H), 0.80–0.50 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.49, 167.47, 167.39, 167.36, 165.51, 164.23, 151.80, 151.64, 150.41, 149.90, 146.23, 136.08, 135.98, 135.81, 135.74, 131.24, 130.20, 130.06, 129.62, 129.58, 129.51, 129.47, 128.24, 128.18, 126.68, 123.51, 123.25, 123.10, 116.42, 116.37, 116.30, 47.26, 45.98, 42.64, 42.48, 41.23, 37.43, 37.37, 36.00, 35.96, 35.85, 35.81, 31.73, 31.36, 31.08, 31.03; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −106.93, −107.00; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₀FN₄O₃S ([M+H]⁺) 545.2017, found 545.2026.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-4-cyanobenzenesulfonamide (C-4-10). Following General Procedure 3, 75-10 (1.00 g, 2.13 mmol) was first treated with TFA (5 mL) in CH₂Cl₂ (3 mL), and the intermediate obtained was reacted with 7·TFA (0.76 g, 2.56 mmol) using EDCI (1.02 g, 5.33 mmol), HOBT (22 mg, 0.160 mmol), and DIPEA (1.65 g, 12.8 mmol) in dried THF (10 mL). Purification by column chromatography (EtOAc) gave C-4-10. White foam, 0.77 g (66%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.78–8.77 (m, 1H), 8.65–8.63 (m, 2H), 8.14–8.10 (m, 2H), 7.98–7.95 (m, 3H), 7.83–7.78 (m, 1H), 7.57–7.55 (m, 3H), 7.19–7.17 (m, 3H), 7.06–6.97 (m, 2H), 3.86–3.68 (m, 1H), 3.40 (m, 0.60H), 3.28–3.12 (m, 1H), 2.99–2.98 (m, 1H), 2.80 (m, 0.49H), 2.70–2.58 (m, 2H), 2.42–2.34 (m, 1.59H), 1.47–1.44 (m, 0.58H), 1.39 (m, 0.81H), 1.32–1.23 (m, 1H), 1.17–1.13 (m, 1.55H), 0.76–0.55 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.51, 167.43, 151.78, 151.65, 150.49, 149.92, 149.88, 146.31, 146.27, 144.13, 136.06, 136.03, 135.89, 135.64, 133.05, 132.98, 131.19, 130.15, 129.99, 128.31, 127.49, 127.38, 126.87, 126.81, 123.55, 123.27, 123.21, 117.34, 117.24, 116.14, 47.86, 46.30, 42.65, 42.61, 42.50, 40.94, 37.44, 37.38, 36.08, 35.94, 31.68, 31.29, 31.17, 30.91, 28.64; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₀N₅O₃S ([M+H]⁺) 552.2064, found 552.2067.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-4-methoxybenzenesulfonamide (C-4-11). Following General Procedure 3, 75-11 (0.84 g, 1.85 mmol) was first treated with TFA (4.2 mL) in CH₂Cl₂ (2.5 mL), and the intermediate obtained was reacted with 7·TFA (0.66 g, 2.22 mmol) using EDCI (0.89 g, 4.63 mmol), HOBT (19 mg, 0.139 mmol), and DIPEA (1.43 g, 11.1 mmol) in dried THF (8.4 mL). Purification by column chromatography (EtOAc) gave C-4-11. White foam, 0.84 g (81%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.66–8.64 (m, 2H), 7.84–7.79 (m, 1H), 7.74–7.73 (m, 2H), 7.58–7.54 (m, 3H), 7.49–7.45 (m, 1H), 7.17–7.10 (m, 5H), 7.05–6.96 (m, 2H), 4.11–4.08 (m, 0.29H), 3.85–3.84 (m, 4H), 3.70 (m, 0.49H), 3.25–3.20 (m, 0.65H), 3.18–3.12 (m, 1H), 2.96 (s, 1H), 2.77–2.61 (m, 2H), 2.37–2.31 (m, 1.71H), 1.47–1.44 (m, 0.61H), 1.30–1.23 (m, 1H), 1.11–1.03 (m, 1.63H), 0.80–0.51 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.43, 167.31, 162.78, 151.85, 151.66, 150.34, 149.91, 146.20, 146.17, 136.09, 136.06, 135.95, 135.85, 131.30, 131.14, 130.25, 130.09, 128.91, 128.19, 128.13, 126.57, 123.47, 123.22, 123.03, 114.36, 114.33, 114.27, 55.59, 46.94, 45.80, 42.64, 42.48, 41.46, 37.42, 37.35, 35.94, 35.78, 31.78, 31.53, 31.34, 31.15; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₃N₄O₄S ([M+H]⁺) 557.2217, found 557.2217.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-4-nitrobenzenesulfonamide (C-4-12). Following General Procedure 3, 75-12 (1.00 g, 2.04 mmol) was first treated with TFA (5 mL) in CH₂Cl₂ (3 mL), and the intermediate obtained was reacted with 7·TFA (0.73 g, 2.45 mmol) using EDCI (0.98 g, 5.10 mmol), HOBT (21 mg, 0.153 mmol), and DIPEA (1.58 g, 12.2 mmol) in dried THF (10 mL). Purification by column chromatography (EtOAc) gave C-4-12. Pale yellow foam, 0.92 g (79%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.64–8.63 (m, 2H), 8.47–8.42 (m, 2H), 8.07–7.96 (m, 3H), 7.83–7.78 (m, 1H), 7.57–7.53 (m, 3H), 7.19–7.17 (m, 3H), 7.09–6.98 (m, 2H), 3.86–3.68 (m, 1H), 3.42 (m, 0.49H), 3.31–3.25 (m, 0.66H), 3.17–3.13 (m, 1.57H), 3.03–2.96 (m, 1H), 2.80–2.71 (m, 1H), 2.64–2.63 (m, 1H), 2.44–2.35 (m, 1.51H), 1.48–1.45 (m, 0.59H), 1.34–1.23 (m, 1H), 1.13–1.06 (m, 1.66H), 0.76–0.53 (m, 1H); ¹³C NMR (201 MHz, CDCl₃ + CD₃OD) δ 167.40, 167.28, 151.47, 151.33, 150.17, 149.66, 149.30, 149.15, 146.34, 145.82, 135.99, 135.80, 135.55, 131.07, 130.07, 129.95, 127.86, 127.82, 126.41, 126.34, 124.10, 124.07, 123.63, 123.16, 123.07, 47.13, 46.16, 42.58, 42.44, 41.90, 40.76, 37.32, 37.24, 35.76, 35.62, 31.16, 30.83, 30.61, 30.52; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₀N₅O₅S ([M+H]⁺) 572.1962, found 572.1965.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-3-chlorobenzenesulfonamide (C-4-13). Following General Procedure 3, 75-13 (0.80 g, 1.67 mmol) was first treated with TFA (4 mL) in CH₂Cl₂ (2.4 mL), and the intermediate obtained was reacted with 7·TFA (0.60 g, 2.00 mmol) using EDCI (0.80 g, 4.18 mmol), HOBT (17 mg, 0.125 mmol), and DIPEA (1.29 g, 10.0 mmol) in dried THF (8 mL). Purification by column chromatography (EtOAc) gave C-4-13. White foam, 0.79 g (84%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.78–8.77 (m, 1H), 8.66–8.63 (m, 2H), 7.85–7.73 (m, 5H), 7.68–7.63 (m, 1H), 7.58–7.54 (m, 3H), 7.19–7.17 (m, 3H), 7.07–6.97 (m, 2H), 3.87–3.69 (m, 1H), 3.39 (m, 0.48H), 3.29–3.25 (m, 0.58H), 3.18–3.12 (m, 1H), 3.03–2.95 (m, 1H), 2.82 (m, 0.47H), 2.70–2.56 (m, 2H), 2.43–2.34 (m, 1.44H), 1.48–1.46 (m, 0.58H), 1.34–1.22 (m, 1H), 1.15–1.06 (m, 1.51H), 0.82–0.51 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.46, 167.34, 151.80, 151.58, 150.37, 149.90, 149.82, 146.19, 146.14, 141.46, 136.05, 135.92, 135.86, 135.63, 135.14, 132.69, 131.18, 131.15, 130.50, 130.46, 130.14, 129.99, 128.19, 126.77, 126.70, 126.65, 124.98, 124.81, 123.47, 123.44, 123.21, 123.03, 47.32, 46.01, 42.66, 42.59, 42.48, 41.24, 37.43, 37.33, 35.96, 35.80, 31.68, 31.33, 31.26, 31.01; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₀ClN₄O₃S ([M+H]⁺) 561.1722, found 561.1724.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-2-fluorobenzenesulfonamide (C-4-14). Following General Procedure 3, 75-14 (0.85 g, 1.84 mmol) was first treated with TFA (4.3 mL) in CH₂Cl₂ (2.6 mL), and the intermediate obtained was reacted with 7·TFA (0.66 g, 2.21 mmol) using EDCI (0.88 g, 4.60 mmol), HOBT (19 mg, 0.138 mmol), and DIPEA (1.42 g, 11.0 mmol) in dried THF (8.5 mL). Purification by column chromatography (EtOAc) gave C-4-14. White foam, 0.83 g (83%). ¹H NMR (500 MHz, CD₃OD) δ 8.76 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.67–8.58 (m, 2H), 7.85–7.83 (m, 2H), 7.67–7.65 (m, 3H), 7.56–7.54 (m, 1H), 7.37–7.30 (m, 2H), 7.22–7.17 (m, 3H), 7.09–6.98 (m, 2H), 4.59 (m, 0.24H), 3.98–3.80 (m, 1H), 3.43–3.32 (m, 1H), 3.18–3.08 (m, 1H), 3.04–3.00 (m, 0.53H), 2.90–2.83 (m, 1.49H), 2.68–2.64 (m, 1.78H), 2.52–2.41 (m, 1H), 1.55–1.52 (m, 0.56H), 1.43–1.40 (m, 1H), 1.26–1.20 (m, 1.51H), 1.04–0.62 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.41, 167.27, 159.48, 157.46, 151.85, 151.65, 150.32, 149.88, 146.20, 146.13, 136.05, 136.01, 135.92, 135.82, 135.09, 135.02, 131.33, 131.24, 130.40, 130.14, 129.96, 128.26, 127.64, 127.53, 127.44, 127.34, 126.70, 124.64, 124.54, 123.44, 123.23, 122.96, 116.95, 116.78, 46.86, 45.77, 43.11, 42.58, 42.37, 41.75, 37.33, 37.27, 36.01, 35.90, 31.71, 31.54, 31.35, 31.15; ¹⁹F NMR (471 MHz, CD₃OD) δ −111.64, −111.70; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₀FN₄O₃S ([M+H]⁺) 545.2017, found 545.2019.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-3-fluorobenzenesulfonamide (C-4-15). Following General Procedure 3, 75-15 (0.90 g, 1.95 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.70 g, 2.34 mmol) using EDCI (0.94 g, 4.88 mmol), HOBT (20 mg, 0.146 mmol), and DIPEA (1.51 g, 11.7 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-15. White foam, 0.91 g (86%). ¹H NMR (500 MHz, CD₃OD) δ 8.76 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.66–8.58 (m, 2H), 7.84–7.81 (m, 1H), 7.68–7.53 (m, 6H), 7.39–7.38 (m, 1H), 7.20–7.15 (m, 3H), 7.05–6.93 (m, 2H), 3.98–3.75 (m, 1H), 3.50–3.34 (m, 1H), 3.21–3.08 (m, 1H), 3.03–2.87 (m, 1H), 2.81–2.74 (m, 1H), 2.63–2.52 (m, 2H), 2.49–2.38 (m, 1H), 1.54–1.50 (m, 0.53H), 1.44–1.31 (m, 1H), 1.26–1.18 (m, 1.56H), 0.99–0.61 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.54, 167.44, 163.25, 163.22, 161.59, 161.55, 151.92, 151.72, 150.46, 150.01, 149.95, 146.27, 141.82, 141.78, 136.13, 136.00, 135.97, 135.74, 131.30, 131.28, 131.12, 131.08, 131.04, 130.20, 130.03, 128.31, 126.83, 126.77, 123.53, 123.29, 123.12, 122.70, 122.55, 119.99, 119.85, 114.26, 114.10, 47.47, 46.14, 42.93, 42.67, 42.54, 41.40, 37.47, 37.39, 36.07, 35.92, 31.81, 31.47, 31.43, 31.14; ¹⁹F NMR (471 MHz, CD₃OD) δ −111.98, −111.99; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₀FN₄O₃S ([M+H]⁺) 545.2017, found 545.2021.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2,3,4,5,6-pentafluorobenzenesulfonamide (C-4-16). Following General Procedure 3, 75-16 (0.80 g, 1.50 mmol) was first treated with TFA (4 mL) in CH₂Cl₂ (2.4 mL), and the intermediate obtained was reacted with 7·TFA (0.54 g, 1.80 mmol) using EDCI (0.72 g, 3.75 mmol), HOBT (15 mg, 0.113 mmol), and DIPEA (1.16 g, 9.00 mmol) in dried THF (8 mL). Purification by column chromatography (EtOAc) gave C-4-16. White foam, 0.78 g (85%). ¹H NMR (500 MHz, CD₃OD) δ 8.76 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.64–8.58 (m, 2H), 7.86–7.82 (m, 1H), 7.70–7.66 (m, 2H), 7.57–7.54 (m, 1H), 7.26–7.03 (m, 5H), 4.59 (m, 0.27H), 3.40–3.79 (m, 1H), 3.59–3.37 (m, 1H), 3.23–3.14 (m, 1H), 3.06–2.97 (m, 2H), 2.83–2.69 (m, 1.72H), 2.55–2.45 (m, 1H), 1.59–1.46 (m, 1H), 1.40–1.25 (m, 2H), 1.00–0.69 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.59, 167.50, 152.02, 151.73, 150.57, 150.03, 149.98, 146.47, 146.33, 145.27, 144.84, 143.23, 142.76, 138.93, 136.89, 136.25, 136.06, 135.95, 135.75, 131.35, 131.31, 130.23, 129.93, 128.56, 127.14, 127.04, 123.66, 123.57, 123.46, 123.24, 116.38, 116.25, 116.13, 48.26, 46.34, 43.44, 42.65, 41.12, 37.49, 37.39, 36.28, 36.20, 31.88, 31.60, 31.47, 31.20; ¹⁹F NMR (471 MHz, CD₃OD) δ −139.47–−139.53 (m), −150.30–−150.39 (m), −162.19–−162.34 (m); ESI-HR-MS: (m/z) calcd. for C₃₀H₂₆F₅N₄O₃S ([M+H]⁺) 617.1640, found 617.1643.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2,3,4,5,6-pentamethylbenzenesulfonamide (C-4-17). Following General Procedure 3, 75-17 (0.87 g, 1.69 mmol) was first treated with TFA (4.4 mL) in CH₂Cl₂ (2.6 mL), and the intermediate obtained was reacted with 7·TFA (0.61 g, 2.03 mmol) using EDCI (0.81 g, 4.23 mmol), HOBT (17 mg, 0.128 mmol), and DIPEA (1.31 g, 10.1 mmol) in dried THF (8.7 mL). Purification by column chromatography (EtOAc) gave C-4-17. White solid, 0.85 g (84%). m.p. 212.3–214.1 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.64–8.60 (m, 2H), 7.82–7.78 (m, 1H), 7.57–7.53 (m, 3H), 7.41–7.36 (m, 1H), 7.19–7.17 (m, 3H), 7.06–6.94 (m, 2H), 3.79–3.65 (m, 1H), 3.26–3.23 (m, 1H), 3.08–3.06 (m, 0.50H), 2.92–2.90 (m, 1H), 2.70–2.61 (m, 2H), 2.55–2.54 (m, 0.67H), 2.48 (m, 6.64H), 2.36–2.33 (m, 1.67H), 2.22–2.17 (m, 10H), 1.46–1.23 (m, 0.62H), 1.30–1.23 (m, 1H), 0.75–0.47 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.50, 167.40, 152.18, 151.88, 150.45, 150.15, 146.31, 146.12, 139.68, 136.41, 136.27, 136.20, 136.03, 135.87, 135.65, 134.98, 134.92, 133.89, 133.82, 131.53, 131.38, 130.22, 130.03, 128.46, 126.91, 123.53, 123.48, 123.38, 123.00, 46.35, 45.36, 43.89, 42.76, 42.60, 42.44, 37.44, 36.34, 36.19, 32.11, 32.05, 31.95, 31.72, 18.91, 17.84, 17.81, 17.12, 17.08; ESI-HR-MS: (m/z) calcd. for C₃₀H₂₆F₅N₄O₃S ([M+H]⁺) 597.2894, found 597.2899.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-3,4-difluorobenzenesulfonamide (C-4-18). Following General Procedure 3, 75-18 (0.88 g, 1.83 mmol) was first treated with TFA (4.4 mL) in CH₂Cl₂ (2.6 mL), and the intermediate obtained was reacted with 7·TFA (0.66 g, 2.20 mmol) using EDCI (0.87 g, 4.56 mmol), HOBT (19 mg, 0.137 mmol), and DIPEA (1.42 g, 11.0 mmol) in dried THF (8.8 mL). Purification by column chromatography (EtOAc) gave C-4-18. White foam, 0.79 g (77%). ¹H NMR (500 MHz, CD₃OD) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.67–8.59 (m, 2H), 7.86–7.77 (m, 2H), 7.70–7.65 (m, 3H), 7.58–7.48 (m, 2H), 7.22–7.19 (m, 3H), 7.06–6.95 (m, 2H), 4.59–3.94 (m, 1H), 3.78–3.53 (m, 1H), 3.38–3.34 (m, 0.60H), 3.20–3.11 (m, 1H), 3.05–2.91 (m, 1H), 2.81–2.74 (m, 1H), 2.65 (m, 0.74H), 2.55–2.40 (m, 2H), 1.56–1.52 (m, 0.51H), 1.43–1.34 (m, 1H), 1.28–1.19 (m, 1.62H), 0.96–0.64 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.65, 167.59, 154.16, 154.06, 152.12, 152.01, 151.84, 151.25, 150.61, 150.11, 149.23, 146.38, 136.65, 136.22, 136.03, 135.80, 131.36, 130.21, 130.02, 128.51, 127.09, 127.00, 124.21, 124.00, 123.63, 123.39, 123.30, 118.47, 118.32, 116.95, 116.79, 47.95, 46.37, 43.26, 42.72, 42.62, 41.32, 37.54, 37.47, 36.20, 36.07, 31.95, 31.65, 31.48, 31.19; ¹⁹F NMR (471 MHz, CD₃OD) δ −133.31–−133.43 (m), −136.87–−136.96 (m); ESI-HR-MS: (m/z) calcd. for C₃₀H₂₉F₂N₄O₃S ([M+H]⁺) 563.1923, found 563.1928.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-3,4,5-trifluorobenzenesulfonamide (C-4-19). Following General Procedure 3, 75-19 (0.80 g, 1.60 mmol) was first treated with TFA (4 mL) in CH₂Cl₂ (2.4 mL), and the intermediate obtained was reacted with 7·TFA (0.57 g, 1.92 mmol) using EDCI (0.77 g, 4.00 mmol), HOBT (16 mg, 0.120 mmol), and DIPEA (1.24 g, 9.60 mmol) in dried THF (8 mL). Purification by column chromatography (EtOAc) gave C-4-19. White foam, 0.67 g (72%). ¹H NMR (500 MHz, CD₃OD) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.67–8.58 (m, 2H), 7.86–7.82 (m, 1H), 7.68–7.63 (m, 4H), 7.58–7.55 (m, 1H), 7.23–7.20 (m, 3H), 7.08–7.00 (m, 2H), 4.59 (s, 1H), 4.00–3.95 (m, 0.53H), 3.77–3.57 (m, 1H), 3.40–3.35 (m, 1H), 3.22–3.02 (m, 1.52H), 2.93–2.76 (m, 1.62H), 2.66 (m, 0.69H), 2.59–2.41 (m, 2H), 1.55–1.21 (m, 3H), 0.91–0.66 (m, 1H); ¹³C NMR (151 MHz, CDCl₃ + CD₃OD) δ 167.46, 167.36, 151.69, 151.61, 151.40, 150.23, 149.96, 149.35, 149.22, 146.40, 143.04, 141.31, 136.33, 136.03, 135.83, 135.60, 131.14, 130.12, 130.02, 127.93, 126.49, 123.67, 123.23, 123.12, 111.85, 111.73, 47.26, 46.24, 42.63, 41.95, 40.83, 37.34, 35.79, 35.68, 31.24, 30.94, 30.71, 30.62; ¹⁹F NMR (471 MHz, CD₃OD) δ −132.96–−132.02 (m), −156.32–−156.48 (m); ESI-HR-MS: (m/z) calcd. for C₃₀H₂₈F₃N₄O₃S ([M+H]⁺) 581.1829, found 581.1835.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2,5-difluorobenzenesulfonamide (C-4-20). Following General Procedure 3, 75-20 (0.80 g, 1.66 mmol) was first treated with TFA (4 mL) in CH₂Cl₂ (2.4 mL), and the intermediate obtained was reacted with 7·TFA (0.59 g, 1.99 mmol) using EDCI (0.80 g, 4.15 mmol), HOBT (17 mg, 0.125 mmol), and DIPEA (1.29 g, 9.96 mmol) in dried THF (8 mL). Purification by column chromatography (EtOAc) gave C-4-20. White foam, 0.71 g (76%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.64–8.63 (m, 2H), 8.16–8.10 (m, 1H), 7.83–7.78 (m, 1H), 7.59–7.53 (m, 6H), 7.23–7.17 (m, 3H), 7.11–7.01 (m, 2H), 3.85–3.69 (m, 1H), 3.33–3.27 (m, 1H), 3.18–3.14 (m, 0.76H), 3.04–2.97 (m, 1H), 2.84–2.80 (m, 1H), 2.74–2.66 (m, 1.53H), 2.56–2.53 (m, 1.46H), 2.40–2.37 (m, 0.61H), 1.51–1.47 (m, 0.60H), 1.35–1.28 (m, 1H), 1.16–1.09 (m, 1.60H), 0.84–0.55 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.57, 167.44, 158.84, 156.86, 155.54, 153.56, 152.02, 151.78, 150.49, 150.10, 150.03, 146.33, 146.22, 136.18, 136.03, 135.84, 131.41, 131.33, 130.20, 129.97, 129.04, 126.96, 126.91, 123.57, 123.52, 123.36, 123.09, 121.76, 121.70, 121.57, 121.50, 118.57, 118.51, 118.38, 118.31, 117.36, 117.16, 116.95, 47.40, 46.05, 43.40, 42.66, 42.50, 41.68, 37.43, 37.36, 36.18, 36.08, 31.87, 31.66, 31.56, 31.27; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −115.57–−115.67 (m), −116.19–−116.23 (m); ESI-HR-MS: (m/z) calcd. for C₃₀H₂₉F₂N₄O₃S ([M+H]⁺) 563.1923, found 563.1931.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2,4,5-trifluorobenzenesulfonamide (C-4-21). Following General Procedure 3, 75-21 (0.91 g, 1.83 mmol) was first treated with TFA (4.6 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.66 g, 2.20 mmol) using EDCI (0.87 g, 4.56 mmol), HOBT (19 mg, 0.137 mmol), and DIPEA (1.42 g, 11.0 mmol) in dried THF (9.1 mL). Purification by column chromatography (EtOAc) gave C-4-21. White foam, 0.84 g (79%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.63 (dd, J = 2.0 Hz and 4.5 Hz, 2H), 8.19–8.12 (m, 1H), 7.90–7.78 (m, 3H), 7.57–7.53 (m, 3H), 7.24–7.18 (m, 3H), 7.12–7.01 (m, 2H), 3.85–3.44 (m, 2H), 3.31–3.27 (m, 0.59H), 3.17–3.14 (m, 0.65H), 3.04–2.99 (m, 1H), 2.82–2.78 (m, 1H), 2.73–2.65 (m, 1.49H), 2.55–2.52 (m, 1H), 2.40–2.37 (m, 0.60H), 1.49–1.46 (m, 0.60H), 1.35–1.24 (m, 1H), 1.16–1.08 (m, 1.61H), 0.77–0.58 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.61, 167.49, 155.33, 155.25, 154.24, 153.31, 153.24, 152.16, 151.98, 151.80, 150.55, 150.04, 147.36, 146.39, 145.36, 136.20, 136.11, 136.02, 135.83, 131.40, 130.19, 129.95, 128.55, 128.52, 127.07, 126.99, 124.47, 124.33, 123.60, 123.40, 123.20, 119.13, 118.91, 117.73, 107.65, 107.48, 107.44, 107.26, 47.66, 46.19, 43.42, 42.66, 42.51, 41.51, 37.46, 37.38, 36.20, 36.13, 31.91, 31.61, 31.25; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −110.07–−110.16 (m), −126.25–−126.39 (m), −140.39–−140.47 (m); ESI-HR-MS: (m/z) calcd. for C₃₀H₂₈F₃N₄O₃S ([M+H]⁺) 581.1829, found 581.1837.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-3-chloro-4-fluorobenzenesulfonamide (C-4-22). Following General Procedure 3, 75-22 (0.90 g, 1.81 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.65 g, 2.17 mmol) using EDCI (0.87 g, 4.53 mmol), HOBT (18 mg, 0.136 mmol), and DIPEA (1.41 g, 10.9 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-22. White foam, 0.54 g (51%). ¹H NMR (500 MHz, CD₃OD) δ 8.76 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.67–8.59 (m, 2H), 7.99–7.96 (m, 1H), 7.85–7.78 (m, 2H), 7.67–7.66 (m, 2H), 7.56–7.54 (m, 1H), 7.48–7.42 (m, 1H), 7.21–7.18 (m, 3H), 7.05–6.94 (m, 2H), 3.98–3.76 (m, 1H), 3.55–3.33 (m, 1H), 3.22–3.10 (m, 1H), 3.04–2.89 (m, 1H), 2.80–2.73 (m, 1H), 2.64–2.63 (m, 1H), 2.57–2.39 (m, 2H), 1.54–1.51 (m, 0.52H), 1.43–1.34 (m, 1H), 1.26–1.19 (m, 1.52H), 0.96–0.62 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.63, 161.64, 159.59, 151.86, 150.63, 150.11, 146.44, 136.90, 136.23, 136.05, 135.83, 131.40, 130.21, 130.01, 129.87, 128.57, 127.60, 127.39, 127.11, 123.67, 123.42, 122.66, 122.52, 117.68, 117.51, 48.05, 46.39, 43.42, 42.71, 41.37, 37.50, 36.24, 36.11, 32.00, 31.74, 31.48, 31.21; ¹⁹F NMR (471 MHz, CD₃OD) δ −110.77, −110.81; ESI-HR-MS: (m/z) calcd. for C₃₀H₂₉ClFN₄O₃S ([M+H]⁺) 579.1627, found 579.1637.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2,3,4-trifluorobenzenesulfonamide (C-4-23). Following General Procedure 3, 75-23 (0.85 g, 1.70 mmol) was first treated with TFA (4.3 mL) in CH₂Cl₂ (2.6 mL), and the intermediate obtained was reacted with 7·TFA (0.61 g, 2.04 mmol) using EDCI (0.81 g, 4.25 mmol), HOBT (17 mg, 0.128 mmol), and DIPEA (1.32 g, 10.2 mmol) in dried THF (8.5 mL). Purification by column chromatography (EtOAc) gave C-4-23. White foam, 0.85 g (86%). ¹H NMR (500 MHz, CD₃OD) δ 8.78–8.76 (m, 1H), 8.68–8.58 (m, 2H), 7.87–7.84 (m, 1H), 7.68–7.66 (m, 3H), 7.58–7.54 (m, 1H), 7.32–7.19 (m, 4H), 7.10–7.01 (m, 2H), 3.98–3.80 (m, 1H), 3.50–3.35 (m, 1.44H), 3.20–3.05 (m, 1.59H), 2.92–2.85 (m, 1.51H), 2.68–2.65 (m, 1.60H), 2.54–2.44 (m, 1H), 1.55–1.44 (m, 1H), 1.37–1.34 (m, 0.51H), 1.30–1.24 (m, 1.61H), 0.99–0.69 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.71, 167.61, 155.21, 153.50, 152.06, 151.93, 150.66, 150.16, 149.25, 147.53, 146.49, 141.25, 139.55, 136.28, 136.07, 135.89, 131.49, 130.14, 129.91, 128.75, 127.30, 127.20, 125.63, 125.39, 124.83, 124.40, 123.70, 123.51, 123.36, 112.82, 47.73, 46.31, 43.95, 42.72, 42.54, 41.87, 37.47, 36.36, 36.29, 32.04, 31.89, 31.73, 31.42, 29.81; ¹⁹F NMR (471 MHz, CD₃OD) δ −128.46–−128.60 (m), −132.66–−160.75 (m), −160.30–−160.47 (m); ESI-HR-MS: (m/z) calcd. for C₃₀H₂₈F₃N₄O₃S ([M+H]⁺) 581.1829, found 581.1837.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-3,5-bis(trifluoromethyl)benzenesulfonamide (C-4-24). Following General Procedure 3, 75-24 (0.90 g, 1.55 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.55 g, 1.86 mmol) using EDCI (0.74 g, 3.88 mmol), HOBT (16 mg, 0.116 mmol), and DIPEA (1.20 g, 9.30 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-24. White foam, 0.78 g (76%). ¹H NMR (500 MHz, CD₃OD) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.66–8.59 (m, 2H), 8.39–8.38 (m, 2H), 8.30 (s, 1H), 7.86–7.83 (m, 1H), 7.68–7.67 (m, 2H), 7.57–7.55 (m, 1H), 7.19–7.16 (m, 3H), 7.04–6.93 (m, 2H), 3.95–3.92 (m, 0.52H), 3.76–3.64 (m, 1H), 3.45–3.40 (m, 1H), 3.28–3.12 (m, 1H), 3.05–2.98 (m, 1H), 2.85–2.78 (m, 1H), 2.67–2.58 (m, 1.66H), 2.52–2.41 (m, 1H), 1.56–1.53 (m, 0.54H), 1.44–1.37 (m, 1H), 1.30–1.20 (m, 1.58H), 0.97–0.66 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.72, 152.02, 151.78, 150.66, 150.09, 150.04, 146.39, 143.05, 136.25, 136.14, 135.88, 135.63, 133.34, 133.11, 133.08, 132.88, 132.85, 132.65, 131.25, 131.21, 130.16, 129.97, 128.50, 127.32, 127.15, 127.07, 126.22, 125.19, 123.66, 123.59, 123.45, 123.40, 123.31, 121.64, 121.56, 119.75, 48.47, 46.65, 42.94, 42.72, 40.95, 37.60, 37.49, 36.19, 36.09, 31.82, 31.49, 31.23, 31.00; ¹⁹F NMR (471 MHz, CD₃OD) δ −64.29, −64.33; ESI-HR-MS: (m/z) calcd. for C₃₂H₂₉F₆N₄O₃S ([M+H]⁺) 663.1859, found 663.1865.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2-chloro-4-fluorobenzenesulfonamide (C-4-25). Following General Procedure 3, 75-25 (0.90 g, 1.81 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.65 g, 2.17 mmol) using EDCI (0.87 g, 4.53 mmol), HOBT (18 mg, 0.136 mmol), and DIPEA (1.41 g, 10.9 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-25. White foam, 0.81 g (77%). ¹H NMR (500 MHz, CD₃OD) δ 8.77–8.75 (m, 1H), 8.67–8.59 (m, 2H), 8.07–8.05 (m, 1H), 7.85–7.83 (m, 1H), 7.67–7.66 (m, 2H), 7.57–7.54 (m, 1H), 7.49–7.46 (m, 1H), 7.23–7.19 (m, 4H), 7.10–6.99 (m, 2H), 3.96–3.80 (m, 1H), 3.38–3.32 (m, 1H), 3.17–3.14 (m, 0.49H), 3.10–2.98 (m, 1H), 2.84–2.77 (m, 1.54H), 2.65 (s, 1H), 2.55–2.40 (m, 2H), 1.54–1.51 (m, 0.54H), 1.43–1.33 (m, 1H), 1.25–1.20 (m, 1.59H), 0.98–0.62 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.66, 167.50, 165.71, 163.73, 163.65, 152.04, 151.89, 150.58, 150.16, 146.37, 136.23, 136.16, 135.96, 133.86, 133.78, 133.36, 133.28, 132.93, 132.81, 131.48, 131.40, 130.17, 130.01, 128.65, 127.10, 127.05, 123.61, 123.44, 123.19, 119.41, 119.21, 115.08, 114.91, 114.83, 114.66, 47.04, 46.00, 43.82, 42.68, 42.43, 42.14, 37.39, 36.32, 36.27, 32.04, 31.97, 31.87, 31.60; ¹⁹F NMR (471 MHz, CD₃OD) δ −106.24, −106.34; ESI-HR-MS: (m/z) calcd. for C₃₀H₂₉ClFN₄O₃S ([M+H]⁺) 579.1627, found 579.1633.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-3-cyano-4-fluorobenzenesulfonamide (C-4-26). Following General Procedure 3, 75-26 (0.64 g, 1.31 mmol) was first treated with TFA (3.2 mL) in CH₂Cl₂ (1.9 mL), and the intermediate obtained was reacted with 7·TFA (0.47 g, 1.57 mmol) using EDCI (0.63 g, 3.28 mmol), HOBT (13 mg, 0.098 mmol), and DIPEA (1.02 g, 7.86 mmol) in dried THF (6.4 mL). Purification by column chromatography (EtOAc) gave C-4-26. White foam, 0.55 g (74%). ¹H NMR (500 MHz, CD₃OD) δ 8.77–8.76 (m, 1H), 8.67–8.58 (m, 2H), 8.26–8.24 (m, 1H), 8.18–8.14 (m, 1H), 7.86–7.82 (m, 1H), 7.68–7.66 (m, 2H), 7.62–7.55 (m, 2H), 7.22–7.19 (m, 3H), 7.07–6.96 (m, 2H), 3.98–3.74 (m, 1H), 3.58–3.35 (m, 1H), 3.23–3.12 (m, 1H), 3.06–2.92 (m, 1H), 2.83–2.76 (m, 1H), 2.65 (s, 1H), 2.58–2.40 (m, 2H), 1.54–1.52 (m, 0.53H), 1.46–1.45 (m, 1H), 1.34–1.18 (m, 1.60H), 0.92–0.65 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.66, 166.03, 163.92, 151.88, 151.86, 150.66, 150.12, 146.51, 146.35, 137.67, 136.20, 136.00, 135.76, 134.11, 134.04, 133.85, 133.77, 133.02, 132.89, 131.35, 131.28, 130.23, 130.04, 128.55, 128.47, 127.17, 127.06, 123.67, 123.38, 123.34, 117.88, 117.71, 112.53, 112.42, 102.93, 102.81, 52.44, 48.44, 46.65, 43.06, 42.71, 42.65, 40.86, 37.59, 37.50, 36.23, 36.14, 31.88, 31.58, 31.28, 31.05, 28.82; ¹⁹F NMR (471 MHz, CDCl₃) δ −99.05, −99.22, −107.07; ESI-HR-MS: (m/z) calcd. for C₃₁H₂₉FN₅O₃S ([M+H]⁺) 570.1970, found 570.1976.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-(tert-butyl)benzenesulfonamide (C-4-27). Following General Procedure 3, 75-27 (0.90 g, 1.80 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.64 g, 2.16 mmol) using EDCI (0.86 g, 4.50 mmol), HOBT (18 mg, 0.135 mmol), and DIPEA (1.40 g, 10.8 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-27. White foam, 0.75 g (72%). ¹H NMR (500 MHz, CD₃OD) δ 8.76 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.67–8.59 (m, 2H), 7.84–7.81 (m, 1H), 7.78–7.74 (m, 2H), 7.67–7.66 (m, 2H), 7.63–7.59 (m, 2H), 7.56–7.53 (m, 1H), 7.18–7.16 (m, 3H), 7.04–6.93 (m, 2H), 3.99–3.78 (m, 1H), 3.43–3.35 (m, 0.67H), 3.28–3.26 (m, 0.46H), 3.20–3.05 (m, 1H), 3.02–2.87 (m, 1H), 2.78–2.71 (m, 1H), 2.63 (s, 1H), 2.58–2.51 (m, 1H), 2.48–2.37 (m, 1H), 1.52–1.41 (m, 1.55H), 1.36–1.34 (m, 9H), 1.24–1.18 (m, 1.62H), 1.01–0.58 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.53, 167.42, 156.60, 152.08, 151.83, 150.45, 150.11, 150.05, 146.30, 136.56, 136.17, 136.02, 135.91, 131.46, 130.29, 130.10, 128.32, 126.82, 126.76, 126.28, 126.22, 123.53, 123.33, 123.12, 47.11, 45.85, 43.19, 42.72, 42.61, 41.72, 37.51, 37.41, 36.17, 35.98, 35.18, 31.93, 31.69, 31.60, 31.31, 31.10; ESI-HR-MS: (m/z) calcd. for C₃₄H₃₉N₄O₃S ([M+H]⁺) 583.2737, found 583.2740.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-(trifluoromethyl)benzenesulfonamide (C-4-28). Following General Procedure 3, 75-28 (0.80 g, 1.56 mmol) was first treated with TFA (4 mL) in CH₂Cl₂ (2.4 mL), and the intermediate obtained was reacted with 7·TFA (0.56 g, 1.87 mmol) using EDCI (0.75 g, 3.90 mmol), HOBT (16 mg, 0.117 mmol), and DIPEA (1.21 g, 9.36 mmol) in dried THF (8 mL). Purification by column chromatography (EtOAc) gave C-4-28. White foam, 0.67 g (72%). ¹H NMR (500 MHz, CD₃OD) δ 8.77–8.75 (m, 1H), 8.67–8.58 (m, 2H), 8.04–8.00 (m, 2H), 7.92–7.82 (m, 3H), 7.68–7.66 (m, 2H), 7.56–7.54 (m, 1H), 7.19–7.16 (m, 3H), 7.04–6.93 (m, 2H), 3.98–3.77 (m, 1H), 3.50–3.35 (m, 1H), 3.22–3.09 (m, 1H), 3.04–2.91 (m, 1H), 2.93–2.76 (m, 1H), 2.64–2.61 (m, 1H), 2.58–2.53 (m, 1H), 2.50–2.39 (m, 1H), 1.54–1.51 (m, 0.53H), 1.45–1.32 (m, 1H), 1.28–1.19 (m, 1.67H), 0.99–0.62 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.63, 167.54, 151.99, 151.80, 150.57, 150.06, 146.37, 143.39, 136.18, 136.11, 135.99, 135.74, 134.81, 134.55, 134.28, 131.34, 130.18, 130.00, 128.44, 127.50, 127.39, 127.00, 126.92, 126.43, 124.27, 123.60, 123.37, 123.28, 122.10, 47.81, 46.26, 43.12, 42.69, 42.59, 41.34, 37.52, 37.45, 36.20, 36.04, 31.89, 31.58, 31.42, 31.13; ¹⁹F NMR (471 MHz, DMSO-d₆) δ −65.23, −65.26; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₀F₃N₄O₃S ([M+H]⁺) 595.1985, found 595.1986.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-fluoro-3-(trifluoromethyl)benzenesulfonamide (C-4-29). Following General Procedure 3, 75-29 (0.80 g, 1.51 mmol) was first treated with TFA (4 mL) in CH₂Cl₂ (2.4 mL), and the intermediate obtained was reacted with 7·TFA (0.54 g, 1.81 mmol) using EDCI (0.72 g, 3.78 mmol), HOBT (15 mg, 0.113 mmol), and DIPEA (1.17 g, 9.06 mmol) in dried THF (8 mL). Purification by column chromatography (EtOAc) gave C-4-29. White foam, 0.76 g (82%). ¹H NMR (500 MHz, CD₃OD) δ 8.78–8.76 (m, 1H), 8.67–8.59 (m, 2H), 8.17–8.14 (m, 2H), 7.86–7.83 (m, 1H), 7.68–7.67 (m, 2H), 7.59–7.55 (m, 2H), 7.20–7.18 (m, 3H), 7.05–6.94 (m, 2H), 3.97–3.77 (m, 1H), 3.58–3.35 (m, 1H), 3.22–3.11 (m, 1H), 3.05–2.92 (m, 1H), 2.81–2.74 (m, 1H), 2.66 (s, 1H), 2.59–2.54 (m, 1H), 2.51–2.41 (m, 1H), 1.55–1.52 (m, 0.53H), 1.46–1.33 (m, 1H), 1.28–1.21 (m, 1.56H), 0.96–0.65 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.65, 163.01, 160.91, 151.99, 151.84, 150.64, 150.12, 146.48, 146.39, 136.72, 136.69, 136.23, 136.17, 135.98, 135.76, 133.41, 133.34, 133.10, 133.02, 131.34, 130.18, 129.97, 128.54, 127.16, 127.06, 126.74, 123.65, 123.40, 122.76, 120.59, 119.82, 119.72, 119.55, 119.44, 118.40, 118.21, 48.17, 46.47, 43.25, 42.70, 41.20, 37.56, 37.47, 36.22, 36.10, 31.95, 31.66, 31.41, 31.13; ¹⁹F NMR (471 MHz, CD₃OD) δ −63.08–−63.15 (m), −110.16–−110.26; ESI-HR-MS: (m/z) calcd. for C₃₁H₂₉F₄N₄O₃S ([M+H]⁺) 613.1891, found 613.1885.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-(trifluoromethoxy)benzenesulfonamide (C-4-30). Following General Procedure 3, 75-30 (0.90 g, 1.70 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.61 g, 2.04 mmol) using EDCI (0.81 g, 4.25 mmol), HOBT (17 mg, 0.128 mmol), and DIPEA (1.32 g, 10.2 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-30. White foam, 0.73 g (70%). ¹H NMR (500 MHz, CD₃OD) δ 8.77–8.76 (m, 1H), 8.68–8.59 (m, 2H), 7.97–7.92 (m, 2H), 7.86–7.82 (m, 1H), 7.68–7.67 (m, 2H), 7.57–7.54 (m, 1H), 7.51–7.47 (m, 2H), 7.20–7.17 (m, 3H), 7.05–6.94 (m, 2H), 3.99–3.78 (m, 1H), 3.49–3.34 (m, 1H), 3.22–3.09 (m, 1H), 3.03–2.88 (m, 1H), 2.81–2.75 (m, 1H), 2.64 (s, 1H), 2.60–2.52 (m, 1H), 2.50–2.40 (m, 1H), 1.54–1.42 (m, 1H), 1.36–1.33 (m, 0.52H), 1.27–1.20 (m, 1.49H), 1.00–0.62 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.53, 152.15, 152.14, 152.02, 151.84, 150.56, 150.10, 146.37, 138.13, 136.19, 136.11, 136.04, 135.79, 131.38, 130.21, 130.01, 129.16, 129.04, 128.43, 126.98, 126.90, 123.58, 123.37, 123.26, 121.27, 121.18, 121.11, 47.68, 46.18, 43.19, 42.70, 42.59, 41.43, 37.52, 37.44, 36.19, 36.04, 31.94, 31.62, 31.52, 31.19; ¹⁹F NMR (471 MHz, CD₃OD) δ −59.27, −59.30; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₀F₃N₄O₄S ([M+H]⁺) 611.1934, found 611.1926.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-fluoro-2-(trifluoromethyl)benzenesulfonamide (C-4-31). Following General Procedure 3, 75-31 (0.90 g, 1.70 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.61 g, 2.04 mmol) using EDCI (0.81 g, 4.25 mmol), HOBT (17 mg, 0.128 mmol), and DIPEA (1.32 g, 10.2 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-31. White solid, 0.71 g (68%), m.p. 102.4–103.8 °C. ¹H NMR (500 MHz, CD₃OD) δ 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.67–8.58 (m, 2H), 8.18–8.11 (m, 1H), 7.85–7.82 (m, 1H), 7.75–7.73 (m, 1H), 7.67–7.66 (m, 2H), 7.62–7.55 (m, 2H), 7.24–7.18 (m, 3H), 7.09–6.99 (m, 2H), 3.96–3.78 (m, 1H), 3.49–3.35 (m, 1H), 3.20–3.11 (m, 1H), 3.05–2.86 (m, 2H), 2.67–2.65 (m, 2H), 2.54–2.44 (m, 1H), 1.57–1.54 (m, 0.56H), 1.45–1.34 (m, 1H), 1.30–1.25 (m, 1.63H), 0.99–0.67 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ 167.62, 167.51, 165.30, 165.22, 163.26, 163.17, 151.95, 151.87, 150.56, 150.14, 146.34, 136.20, 136.16, 136.09, 135.86, 135.22, 135.15, 134.63, 134.52, 134.46, 134.22, 131.40, 130.00, 129.84, 128.61, 127.08, 127.01, 123.60, 123.38, 123.27, 119.43, 119.27, 119.15, 118.98, 116.98, 116.93, 116.78, 116.72, 47.61, 46.39, 43.55, 42.67, 42.46, 41.51, 37.43, 37.38, 36.36, 36.30, 31.91, 31.86, 31.80, 31.42; ¹⁹F NMR (471 MHz, CD₃OD) δ −59.22, −106.31, −106.37; ESI-HR-MS: (m/z) calcd. for C₃₁H₂₉F₄N₄O₃S ([M+H]⁺) 613.1891, found 613.1882.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)naphthalene-2-sulfonamide (C-4-32). Following General Procedure 3, 75-32 (0.90 g, 1.82 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.65 g, 2.18 mmol) using EDCI (0.87 g, 4.55 mmol), HOBT (19 mg, 0.137 mmol), and DIPEA (1.41 g, 10.9 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-32. White foam, 0.66 g (63%). ¹H NMR (500 MHz, CD₃OD) δ 8.74–8.73 (m, 1H), 8.63–8.56 (m, 2H), 8.40–8.39 (m, 1H), 8.05–7.95 (m, 3H), 7.87–7.76 (m, 2H), 7.66–7.61 (m, 4H), 7.54–7.49 (m, 1H), 7.11–7.05 (m, 3H), 6.99–6.87 (m, 2H), 3.96–3.75 (m, 1H), 3.45–3.35 (m, 0.68H), 3.29–3.27 (m, 0.44H), 3.17–3.00 (m, 1H), 2.95–2.86 (m, 1H), 2.81–2.75 (m, 1H), 2.62–2.54 (m, 2H), 2.47–2.36 (m, 1H), 1.51–1.49 (m, 0.62H), 1.40–1.33 (m, 1H), 1.22–1.15 (m, 1.75H), 1.00–0.55 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.45, 167.29, 151.90, 151.64, 150.31, 149.99, 149.87, 146.17, 146.13, 136.36, 136.03, 135.98, 135.93, 135.73, 134.64, 132.07, 131.96, 131.27, 130.17, 130.02, 129.58, 129.22, 129.06, 128.85, 128.31, 128.12, 127.83, 127.62, 126.61, 126.55, 123.43, 123.20, 123.01, 121.90, 47.10, 45.91, 42.80, 42.60, 42.47, 41.48, 37.42, 37.33, 36.00, 35.82, 31.74, 31.43, 31.35, 31.09; ESI-HR-MS: (m/z) calcd. for C₃₄H₃₃N₄O₃S ([M+H]⁺) 577.2268, found 577.2266.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)naphthalene-1-sulfonamide (C-4-33). Following General Procedure 3, 75-33 (0.82 g, 1.66 mmol) was first treated with TFA (4.1 mL) in CH₂Cl₂ (2.5 mL), and the intermediate obtained was reacted with 7·TFA (0.59 g, 1.99 mmol) using EDCI (0.80 g, 4.15 mmol), HOBT (17 mg, 0.127 mmol), and DIPEA (1.29 g, 9.96 mmol) in dried THF (8.2 mL). Purification by column chromatography (EtOAc) gave C-4-33. White solid, 0.69 g (72%). m.p. 121.2–122.8 °C. ¹H NMR (500 MHz, CD₃OD) δ 8.80–8.77 (m, 1H), 8.74 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.65–8.56 (m, 2H), 8.16–8.11 (m, 2H), 8.02–8.00 (m, 1H), 7.79–7.74 (m, 1H), 7.72–7.69 (m, 1H), 7.65–7.61 (m, 3H), 7.58–7.51 (m, 2H), 7.10–7.06 (m, 1H), 7.05–7.02 (m, 2H), 6.90–6.77 (m, 2H), 3.88–3.72 (m, 1H), 3.12–3.02 (m, 1.49H), 2.86–2.85 (m, 1H), 2.73–2.63 (m, 1.58H), 2.55 (s, 1H), 2.46–2.27 (m, 2H), 1.41–1.39 (m, 0.57H), 1.34–1.24 (m, 1H), 1.15–1.02 (m, 1.53H), 0.93–0.42 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.40, 167.27, 151.94, 151.68, 150.36, 150.05, 149.95, 146.23, 146.12, 136.07, 135.94, 135.73, 134.35, 134.30, 134.20, 134.11, 131.36, 131.26, 130.08, 129.91, 129.73, 129.40, 129.22, 128.41, 128.35, 128.20, 127.90, 127.01, 126.94, 126.63, 124.34, 124.14, 124.11, 123.47, 123.44, 123.29, 122.99, 46.70, 45.66, 43.35, 42.58, 42.38, 42.06, 37.29, 37.24, 35.99, 35.85, 31.84, 31.78, 31.48, 31.28; ESI-HR-MS: (m/z) calcd. for C₃₄H₃₃N₄O₃S ([M+H]⁺) 577.2268, found 577.2267.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-cyclohexylbenzenesulfonamide (C-4-34). Following General Procedure 3, 75-34 (0.90 g, 1.71 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.61 g, 2.05 mmol) using EDCI (0.82 g, 4.28 mmol), HOBT (17 mg, 0.128 mmol), and DIPEA (1.33 g, 10.3 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-34. White foam, 0.88 g (85%). ¹H NMR (500 MHz, CD₃OD) δ 8.76–8.75 (m, 1H), 8.67–8.58 (m, 2H), 7.84–7.80 (m, 1H), 7.76–7.72 (m, 2H), 7.67–7.65 (m, 2H), 7.56–7.53 (m, 1H), 7.43–7.39 (m, 2H), 7.18–7.16 (m, 3H), 7.04–6.92 (m, 2H), 3.99–3.78 (m, 1H), 3.39–3.35 (m, 0.74H), 3.27–3.15 (m, 1H), 3.09–2.97 (m, 1H), 2.88–2.85 (m, 0.48H), 2.77–2.70 (m, 1H), 2.62–2.60 (m, 2H), 2.57–2.53 (m, 1H), 2.47–2.37 (m, 1H), 1.87–1.83 (m, 4H), 1.78–1.75 (m, 1H), 1.51–1.43 (m, 5H), 1.34–1.17 (m, 3H), 1.00–0.56 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.44, 167.31, 153.31, 151.96, 151.70, 150.34, 150.02, 149.92, 146.20, 146.14, 136.82, 136.09, 135.94, 135.83, 131.36, 131.30, 130.23, 130.06, 128.18, 127.65, 127.59, 126.96, 126.89, 126.62, 126.56, 123.45, 123.42, 123.24, 123.02, 46.98, 45.74, 44.40, 42.92, 42.64, 42.51, 41.54, 37.44, 37.34, 36.03, 35.84, 34.02, 33.99, 31.80, 31.55, 31.41, 31.17, 26.55, 25.85; ESI-HR-MS: (m/z) calcd. for C₃₆H₄₁N₄O₃S ([M+H]⁺) 609.2894, found 609.2893.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-3-(methylsulfonyl)benzenesulfonamide (C-4-35). Following General Procedure 3, 75-35 (0.90 g, 1.72 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.61 g, 2.06 mmol) using EDCI (0.82 g, 4.30 mmol), HOBT (17 mg, 0.129 mmol), and DIPEA (1.33 g, 10.3 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-35. White foam, 0.60 g (58%). ¹H NMR (500 MHz, CD₃OD) δ 8.76–8.75 (m, 1H), 8.67–8.58 (m, 2H), 8.40 (s, 1H), 8.23–8.13 (m, 2H), 7.85–7.82 (m, 2H), 7.67–7.65 (m, 2H), 7.56–7.54 (m, 1H), 7.19–7.17 (m, 3H), 7.04–6.93 (m, 2H), 3.95–3.74 (m, 1H), 3.55–3.37 (m, 1H), 3.21–3.17 (m, 3.52H), 3.13–3.08 (m, 0.60H), 3.02–2.91 (m, 1H), 2.83–2.76 (m, 1H), 2.64–2.53 (m, 2H), 2.49–2.39 (m, 1H), 1.53–1.50 (m, 0.57H), 1.42–1.33 (m, 1H), 1.26–1.19 (m, 1.62H), 0.96–0.66 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.57, 167.49, 151.90, 151.76, 150.49, 150.06, 149.98, 146.30, 141.99, 141.85, 136.19, 136.12, 136.02, 135.76, 131.94, 131.78, 131.31, 131.15, 131.12, 130.67, 130.63, 130.27, 130.11, 128.37, 126.88, 126.81, 126.01, 123.59, 123.28, 123.24, 47.97, 46.42, 44.26, 44.20, 42.67, 42.57, 40.89, 37.52, 37.42, 36.12, 35.99, 31.75, 31.34, 31.25, 30.99; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₃N₄O₅S₂ ([M+H]⁺) 605.1887, found 605.1887.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-n-propylbenzenesulfonamide (C-4-36). Following General Procedure 3, 75-36 (0.90 g, 1.85 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.66 g, 2.22 mmol) using EDCI (0.89 g, 4.63 mmol), HOBT (19 mg, 0.139 mmol), and DIPEA (1.43 g, 11.1 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-36. White foam, 0.81 g (77%). ¹H NMR (500 MHz, CD₃OD) δ 8.75–8.74 (m, 1H), 8.66–8.58 (m, 2H), 7.83–7.80 (m, 1H), 7.76–7.71 (m, 2H), 7.66–7.65 (m, 2H), 7.55–7.52 (m, 1H), 7.39–7.35 (m, 2H), 7.18–7.16 (m, 3H), 7.04–6.92 (m, 2H), 3.97–3.76 (m, 1H), 3.43–3.35 (m, 0.59H), 3.29–3.26 (m, 0.43H), 3.19–3.15 (m, 0.50H), 3.09–2.96 (m, 1H), 2.90–2.86 (m, 0.51H), 2.77–2.73 (m, 1H), 2.69–2.62 (m, 3H), 2.57–2.50 (m, 1H), 2.47–2.37 (m, 1H), 1.69–1.63 (m, 2H), 1.52–1.49 (m, 0.62H), 1.40–1.33 (m, 1H), 1.24–1.17 (m, 1.65H), 1.01–0.92 (m, 3.59H), 0.62–0.58 (m, 0.58H); ¹³C NMR (151 MHz, CDCl₃ + CD₃OD) δ 168.74, 168.58, 152.88, 152.61, 151.35, 150.44, 150.32, 148.98, 147.84, 138.62, 137.57, 137.32, 137.23, 132.55, 132.50, 131.45, 131.40, 130.08, 128.90, 127.81, 127.35, 127.30, 124.92, 124.56, 124.40, 48.23, 47.07, 43.90, 43.83, 43.37, 41.88, 38.53, 38.47, 36.90, 36.76, 32.48, 32.35, 31.82, 25.12, 14.07; ESI-HR-MS: (m/z) calcd. for C₃₃H₃₇N₄O₃S ([M+H]⁺) 569.2581, found 569.2582.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2,4,6-triisopropylbenzenesulfonamide (C-4-37). Following General Procedure 3, 75-37 (0.90 g, 1.58 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.57 g, 1.90 mmol) using EDCI (0.76 g, 3.95 mmol), HOBT (16 mg, 0.119 mmol), and DIPEA (1.23 g, 9.48 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-37. White foam. 0.88 g (85%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.66–8.60 (m, 2H), 7.82–7.81 (m, 1H), 7.59–7.48 (m, 4H), 7.22 (s, 2H), 7.05–6.92 (m, 3H), 4.16–4.10 (m, 2H), 3.79–3.74 (m, 1H), 3.28–3.09 (m, 1.47H), 2.94–2.89 (m, 2H), 2.73–2.69 (m, 1H), 2.64–2.62 (m, 1.48H), 2.53–2.52 (m, 0.43H), 2.36–2.33 (m, 0.58H), 1.51–1.49 (m, 0.55H), 1.35–1.28 (m, 1H), 1.20–1.18 (m, 6.60H), 1.17–1.07 (m, 14H), 0.86–0.49 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.39, 152.96, 152.14, 151.80, 150.42, 150.05, 146.30, 146.09, 136.17, 136.01, 135.94, 132.20, 131.43, 131.29, 130.14, 129.98, 128.41, 126.78, 123.93, 123.54, 123.43, 123.34, 122.94, 46.03, 45.38, 43.28, 42.74, 42.65, 42.50, 37.43, 36.37, 36.12, 34.10, 32.16, 31.91, 31.70, 31.63, 29.69, 25.00, 24.98, 23.56, 23.55; ESI-HR-MS: (m/z) calcd. for C₃₉H₄₉N₄O₃S ([M+H]⁺) 653.3520, found 653.3521.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-[1,1′-biphenyl]-4-sulfonamide (C-4-38). Following General Procedure 3, 75-38 (0.90 g, 1.73 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.62 g, 2.08 mmol) using EDCI (0.83 g, 4.33 mmol), HOBT (18 mg, 0.130 mmol), and DIPEA (1.34 g, 10.4 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-38. White solid, 0.63 g (60%). m.p. 215.5–216.4 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.77–8.76 (m, 1H), 8.65–8.64 (m, 2H), 7.93–7.87 (m, 4H), 7.83–7.67 (m, 4H), 7.57–7.51 (m, 5H), 7.46–7.43 (m, 1H), 7.17–7.14 (m, 3H), 7.07–6.97 (m, 2H), 3.88–3.71 (m, 1H), 3.39–3.37 (m, 0.44H), 3.28–3.24 (m, 0.60H), 3.18–3.13 (m, 0.51H), 3.00–2.98 (m, 1H), 2.81–2.68 (m, 1H), 2.64–2.60 (m, 2H), 2.45–2.44 (m, 1H), 2.38–2.35 (m, 0.53H), 1.50–1.47 (m, 0.57H), 1.33–1.29 (m, 1H), 1.15–1.06 (m, 1.62H), 0.82–0.51 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.61, 167.51, 152.14, 151.88, 150.52, 150.24, 150.13, 146.33, 146.27, 145.80, 145.75, 139.21, 139.10, 138.14, 136.21, 136.16, 136.10, 135.92, 131.47, 131.42, 130.28, 130.08, 129.19, 128.71, 128.64, 128.46, 128.44, 127.95, 127.87, 127.55, 127.47, 127.38, 127.33, 126.93, 126.85, 123.59, 123.55, 123.38, 123.18, 47.39, 46.08, 43.40, 42.75, 42.62, 41.77, 37.55, 37.46, 36.25, 36.07, 32.01, 31.73, 31.37; ESI-HR-MS: (m/z) calcd. for C₃₆H₃₅N₄O₃S ([M+H]⁺) 603.2424, found 603.2425.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-methylbenzenesulfonamide (C-4-39). Following General Procedure 3, 75-39 (1.00 g, 2.18 mmol) was first treated with TFA (5 mL) in CH₂Cl₂ (3 mL), and the intermediate obtained was reacted with 7·TFA (0.78 g, 2.62 mmol) using EDCI (1.04 g, 5.45 mmol), HOBT (22 mg, 0.164 mmol), and DIPEA (1.69 g, 13.1 mmol) in dried THF (10 mL). Purification by column chromatography (EtOAc) gave C-4-39. White foam, 0.95 g (81%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (d, J = 5.0 Hz, 1H), 8.66–8.64 (m, 2H), 7.84–7.79 (m, 1H), 7.70–7.67 (m, 2H), 7.57–7.52 (m, 4H), 7.42–7.39 (m, 2H), 7.18–7.16 (m, 3H), 7.06–6.96 (m, 2H), 3.86–3.70 (m, 1H), 3.25–3.11 (m, 1H), 2.96–2.77 (m, 1.71H), 2.64–2.54 (m, 2H), 2.40–2.32 (m, 5.46H), 1.47–1.44 (m, 0.61H), 1.31–1.27 (m, 1H), 1.11–1.04 (m, 1.66H), 0.81–0.51 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.38, 167.25, 151.82, 151.60, 150.28, 149.89, 149.82, 146.15, 146.10, 143.40, 136.56, 136.55, 136.01, 135.88, 135.77, 131.27, 131.21, 130.19, 130.02, 129.72, 129.67, 128.09, 126.80, 126.73, 126.55, 126.49, 123.41, 123.17, 122.96, 46.89, 45.75, 42.74, 42.58, 42.43, 41.44, 37.36, 37.28, 35.92, 35.75, 31.70, 31.45, 31.28, 31.08, 21.40, 21.39; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₃N₄O₃S ([M+H]⁺) 541.2268, found 541.2265.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-ethylbenzenesulfonamide (C-4-40). Following General Procedure 3, 75-40 (0.90 g, 1.90 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.68 g, 2.28 mmol) using EDCI (0.91 g, 4.75 mmol), HOBT (19 mg, 0.143 mmol), and DIPEA (1.47 g, 11.4 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-40. White foam, 0.73 g (69%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 4.5 Hz, 1H), 8.66–8.64 (m, 2H), 7.84–7.79 (m, 1H), 7.72–7.69 (m, 2H), 7.58–7.54 (m, 4H), 7.46–7.42 (m, 2H), 7.17–7.15 (m, 3H), 7.05–6.95 (m, 2H), 3.87–3.70 (m, 1H), 3.24–3.11 (m, 1H), 2.96–2.75 (m, 1.72H), 2.71–2.66 (m, 2H), 2.64–2.61 (m, 1.56H), 2.55–2.52 (m, 0.62H), 2.39–2.32 (m, 1.69H), 1.47–1.44 (m, 0.64H), 1.31–1.26 (m, 1H), 1.22–1.18 (m, 3.49H), 1.11–1.04 (m, 2H), 0.80–0.50 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.43, 167.31, 151.92, 151.68, 150.33, 149.97, 149.89, 149.57, 146.20, 146.15, 136.78, 136.06, 135.93, 135.82, 131.33, 131.28, 130.22, 130.05, 128.63, 128.58, 128.16, 126.96, 126.89, 126.60, 126.55, 123.45, 123.22, 123.01, 46.97, 45.79, 42.86, 42.63, 42.49, 41.54, 37.42, 37.33, 35.99, 35.82, 31.79, 31.54, 31.38, 31.16, 28.68, 15.06; ESI-HR-MS: (m/z) calcd. for C₃₂H₃₅N₄O₃S ([M+H]⁺) 555.2424, found 555.2421.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-isopropylbenzenesulfonamide (C-4-41). Following General Procedure 3, 75-41 (1.00 g, 2.05 mmol) was first treated with TFA (5 mL) in CH₂Cl₂ (3 mL), and the intermediate obtained was reacted with 7·TFA (0.73 g, 2.46 mmol) using EDCI (0.98 g, 5.13 mmol), HOBT (21 mg, 0.154 mmol), and DIPEA (1.59 g, 12.3 mmol) in dried THF (10 mL). Purification by column chromatography (EtOAc) gave C-4-41. White foam, 0.62 g (53%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.66–8.64 (m, 2H), 7.84–7.79 (m, 1H), 7.73–7.71 (m, 2H), 7.58–7.53 (m, 4H), 7.49–7.45 (m, 2H), 7.16–7.14 (m, 3H), 7.06–6.95 (m, 2H), 3.89–3.70 (m, 1H), 3.23–3.10 (m, 1H), 3.00–2.95 (m, 2H), 2.78–2.75 (m, 0.48H), 2.66–2.53 (m, 2H), 2.47–2.32 (m, 2H), 1.47–1.44 (m, 0.58H), 1.31–1.21 (m, 7.51H), 1.14–1.04 (m, 1.66H), 0.82–0.47 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.49, 167.36, 154.20, 152.00, 151.75, 150.39, 150.07, 149.99, 146.25, 146.19, 136.94, 136.13, 135.98, 135.87, 131.40, 131.34, 130.27, 130.10, 128.21, 127.33, 127.27, 127.06, 126.99, 126.64, 123.51, 123.46, 123.28, 123.06, 47.00, 45.79, 42.96, 42.69, 42.56, 41.61, 37.48, 37.38, 36.07, 35.89, 34.10, 31.85, 31.61, 31.46, 31.23, 23.64, 23.62; ESI-HR-MS: (m/z) calcd. for C₃₃H₃₇N₄O₃S ([M+H]⁺) 569.2581, found 569.2581.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-3-isopropylbenzenesulfonamide (C-4-42). Following General Procedure 3, 75-42 (0.90 g, 1.85 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.66 g, 2.22 mmol) using EDCI (0.89 g, 4.63 mmol), HOBT (19 mg, 0.139 mmol), and DIPEA (1.43 g, 11.1 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-42. White foam, 0.80 g (76%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 1.8 Hz, 1H), 8.65 (dd, J = 2.0 Hz and 4.5 Hz, 2H), 7.83–7.79 (m, 1H), 7.68–7.67 (m, 1H), 7.62–7.60 (m, 2H), 7.57–7.53 (m, 5H), 7.17–7.15 (m, 3H), 7.05–6.95 (m, 2H), 3.84–3.68 (m, 1H), 3.23–3.12 (m, 1H), 3.02–2.93 (m, 2H), 2.77–2.75 (m, 0.47H), 2.64–2.59 (m, 1.54H), 2.56–2.53 (m, 0.65H), 2.48–2.41 (m, 1.43H), 2.34–2.32 (m, 0.59H), 1.47–1.44 (m, 0.58H), 1.31–1.28 (m, 1H), 1.22–1.21 (m, 6.51H), 1.13–1.03 (m, 1.63H), 0.85–0.47 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.55, 167.45, 152.10, 151.83, 150.47, 150.16, 150.08, 146.31, 146.20, 139.53, 136.19, 136.11, 136.02, 135.88, 131.46, 131.38, 131.10, 130.25, 130.06, 129.27, 129.25, 128.36, 126.83, 126.77, 124.81, 124.74, 124.45, 124.32, 123.56, 123.49, 123.35, 123.09, 47.12, 45.91, 43.24, 42.70, 42.60, 41.81, 37.50, 37.40, 36.15, 35.97, 34.08, 31.97, 31.74, 31.60, 31.38, 23.80, 23.77; ESI-HR-MS: (m/z) calcd. for C₃₃H₃₇N₄O₃S ([M+H]⁺) 569.2581, found 569.2582.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-2-methylbenzenesulfonamide (C-4-43). Following General Procedure 3, 75-43 (0.90 g, 1.96 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.70 g, 2.35 mmol) using EDCI (0.94 g, 4.90 mmol), HOBT (20 mg, 0.147 mmol), and DIPEA (1.53 g, 11.8 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-43. White foam, 0.50 g (47%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.66–8.62 (m, 2H), 7.82–7.69 (m, 3H), 7.57–7.51 (m, 4H), 7.42–7.37 (m, 2H), 7.21–7.17 (m, 3H), 7.08–6.98 (m, 2H), 3.83–3.69 (m, 1H), 3.25–3.20 (m, 1H), 3.10–3.07 (m, 0.44H), 2.96 (s, 1H), 2.74–2.70 (m, 1H), 2.62–2.53 (m, 4.65H), 2.47–2.35 (m, 2H), 1.48–1.45 (m, 0.59H), 1.33–1.23 (m, 1H), 1.13–1.05 (m, 1.63H), 0.83–0.52 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.46, 167.34, 151.97, 151.74, 150.41, 150.06, 149.99, 146.26, 146.15, 143.55, 137.75, 137.56, 136.74, 136.69, 136.17, 136.12, 136.00, 132.86, 132.83, 132.67, 132.64, 131.39, 131.27, 130.25, 130.16, 130.06, 129.97, 129.83, 129.78, 129.22, 128.96, 128.41, 128.37, 128.26, 126.92, 126.84, 126.78, 126.40, 126.25, 123.51, 123.48, 123.31, 123.28, 123.02, 46.84, 45.83, 43.45, 42.66, 42.45, 42.12, 37.34, 36.18, 36.06, 31.86, 31.77, 31.58, 31.50, 31.35, 20.23; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₃N₄O₃S ([M+H]⁺) 541.2268, found 541.2282.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)-4-hydroxybenzenesulfonamide (C-4-44). Following General Procedure 3, 75-44 (0.90 g, 1.95 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.70 g, 2.34 mmol) using EDCI (0.94 g, 4.88 mmol), HOBT (20 mg, 0.146 mmol), and DIPEA (1.51 g, 11.7 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-44. White foam, 0.11 g (10%). ¹H NMR (600 MHz, DMSO-d₆) δ 10.38 (s, 1H), 8.78–8.77 (m, 1H), 8.65–8.64 (m, 2H), 7.84–7.79 (m, 1H), 7.62–7.55 (m, 5H), 7.37–7.35 (m, 1H), 7.17–7.16 (m, 3H), 7.05–7.04 (m, 1H), 6.96–6.89 (m, 3H), 3.86–3.70 (m, 1H), 3.23–3.17 (m, 1H), 3.12–3.10 (m, 0.45H), 2.96 (s, 1H), 2.78–2.58 (m, 2H), 2.48–2.31 (m, 2.46H), 1.46–1.43 (m, 0.54H), 1.30–1.23 (m, 1H), 1.10–1.02 (m, 1.52H), 0.81–0.49 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 167.60, 161.61, 151.69, 150.65, 149.51, 149.24, 147.20, 146.91, 136.29, 136.11, 135.97, 131.40, 130.41, 130.28, 129.77, 129.32, 128.45, 126.90, 123.97, 123.88, 123.72, 116.38, 116.22, 46.73, 46.12, 43.20, 42.99, 42.69, 42.38, 37.68, 36.09, 36.02, 31.98, 31.49, 29.89, 29.81, 29.72, 29.63, 29.43; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₁N₄O₄S ([M+H]⁺) 543.2061, found 543.2061.

Synthesis of 4-(N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)sulfamoyl)benzamide (C-4-45). Following General Procedure 3, 75-45 (0.90 g, 1.85 mmol) was first treated with TFA (4.5 mL) in CH₂Cl₂ (2.7 mL), and the intermediate obtained was reacted with 7·TFA (0.66 g, 2.22 mmol) using EDCI (0.89 g, 4.63 mmol), HOBT (19 mg, 0.139 mmol), and DIPEA (1.43 g, 11.1 mmol) in dried THF (9 mL). Purification by column chromatography (EtOAc) gave C-4-45. White foam, 0.77 g (73%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (d, J = 4.5 Hz, 1H), 8.66–8.63 (m, 2H), 8.22–8.19 (m, 1H), 8.09–8.05 (m, 2H), 7.89–7.86 (m, 2H), 7.83–7.74 (m, 2H), 7.63 (s, 1H), 7.57–7.53 (m, 3H), 7.18–7.15 (m, 3H), 7.05–6.96 (m, 2H), 3.88–3.68 (m, 1H), 3.27–3.11 (m, 1H), 3.02–2.80 (m, 2H), 2.70–2.56 (m, 2.42H), 2.43–2.34 (m, 1.51H), 1.48–1.45 (m, 0.59H), 1.22–1.19 (m, 1H), 1.16–1.05 (m, 1.58H), 0.82–0.51 (m, 1H); ¹³C NMR (151 MHz, CDCl₃) δ 169.04, 168.77, 167.51, 167.41, 151.51, 150.37, 149.40, 146.61, 146.44, 142.77, 142.49, 137.16, 136.17, 135.98, 135.78, 131.22, 130.28, 130.11, 128.44, 128.10, 126.80, 126.58, 123.80, 123.30, 54.08, 47.11, 46.25, 42.75, 42.48, 42.26, 41.16, 37.45, 35.83, 31.45, 31.09, 30.94, 30.76, 17.55; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₂N₅O₄S ([M+H]⁺) 570.2170, found 570.2171.

Synthesis of methyl 4-(N-((1-([2,4′-bipyridine]-3-carbonyl)-4-(cyclohexa-1,5-dien-1-ylmethyl)piperidin-4-yl)methyl)sulfamoyl)benzoate (76). Following General Procedure 3, 75-46 (1.90 g, 3.78 mmol) was first treated with TFA (9.5 mL) in CH₂Cl₂ (5.7 mL), and the intermediate obtained was reacted with 7·TFA (1.35 g, 4.54 mmol) using EDCI (1.81 g, 9.45 mmol), HOBT (38 mg, 0.284 mmol), and DIPEA (2.93 g, 22.7 mmol) in dried THF (19 mL). Purification by column chromatography (EtOAc) gave 76. White foam, 1.91 g (86%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (dd, J = 1.5 Hz and 5.0 Hz, 1H), 8.64–8.63 (m, 2H), 8.19–8.14 (m, 2H), 7.95–7.92 (m, 2H), 7.86–7.78 (m, 2H), 7.57–7.53 (m, 3H), 7.18–7.17 (m, 3H), 7.11–6.97 (m, 2H), 3.91 (s, 3H), 3.86–3.68 (m, 1H), 3.26–2.98 (m, 2.58H), 2.79–2.67 (m, 1H), 2.64–2.59 (m, 2H), 2.44–2.34 (m, 1.50H), 1.45–1.30 (m, 1H), 1.12–1.05 (m, 1.67H), 0.80–0.54 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 167.48, 167.36, 165.56, 165.47, 151.85, 151.63, 150.40, 149.95, 149.87, 146.21, 146.19, 143.68, 136.07, 135.96, 135.92, 135.67, 133.72, 131.22, 130.33, 130.29, 130.15, 129.99, 128.23, 126.84, 126.75, 126.68, 123.48, 123.24, 123.07, 60.37, 52.64, 47.46, 46.09, 42.77, 42.60, 42.48, 41.25, 37.41, 37.33, 36.02, 35.86, 31.70, 31.45, 31.30, 30.99, 22.53, 20.98, 14.10, 14.05; ESI-HR-MS: (m/z) calcd. for C₃₂H₃₃N₄O₅S ([M+H]⁺) 585.2166, found 585.2164.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-4-aminobenzenesulfonamide (C-4-46). Following the procedure for the synthesis of 10 from 9, C-4-46 was prepared from C-4-12 (0.40 g, 0.700 mmol) using 10% Pd/C (40 mg) in MeOH (4 mL). Purification by column chromatography (EtOAc) gave C-4-46. Pale yellow solid, 0.15 g (40%). m.p. 125.4–127.6 °C. 1H NMR (500 MHz, CD₃OD) δ 8.77–8.76 (m, 1H), 8.68–8.60 (m, 2H), 7.85–7.83 (m, 1H), 7.67–7.66 (m, 2H), 7.58–7.55 (m, 1H), 7.52–7.47 (m, 2H), 7.21–7.19 (m, 3H), 7.06–6.93 (m, 2H), 6.72–6.68 (m, 2H), 3.99–3.96 (m, 1H), 3.26–3.17 (m, 1H), 3.05–2.99 (m, 1H), 2.86–2.83 (m, 0.58H), 2.73–2.63 (m, 2H), 2.50–2.37 (m, 2H), 1.53–1.50 (m, 0.67H), 1.42–1.34 (m, 1H), 1.23–1.20 (m, 1.61H), 1.03–0.86 (m, 1H), 0.62–0.60 (m, 0.58H); ¹³C NMR (151 MHz, CD₃OD) δ 169.06, 168.94, 154.09, 153.23, 152.90, 151.60, 151.58, 150.62, 150.54, 148.25, 138.00, 137.77, 137.61, 137.51, 132.90, 132.83, 131.69, 129.96, 129.08, 127.50, 127.22, 125.22, 124.88, 124.69, 114.50, 48.20, 47.12, 44.17, 43.61, 42.14, 38.74, 37.03, 36.90, 32.84, 32.75, 32.11; ESI-HR-MS: (m/z) calcd. for C₃₀H₃₂N₅O₃S ([M+H]⁺) 542.2220, found 542.2219.

Synthesis of 4-(N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)sulfamoyl)benzoic acid (C-4-47). Following the procedure for the synthesis of 14 from 13, C-4-47 was prepared from 76 (0.50 g, 0.855 mmol) using NaOH (68 mg, 1.71 mmol) dissolved in H₂O (0.12 mL) in MeOH (4 mL), followed by acidification by concentrated HCl (0.14 mL). White solid, 0.20 g (41%). ¹H NMR (500 MHz, DMSO-d₆) δ 8.94–8.85 (m, 3H), 8.14–8.08 (m, 4H), 7.94–7.92 (m, 4H), 7.69–7.66 (m, 1H), 7.18–7.16 (m, 3H), 7.02 (s, 2H), 3.77–3.40 (m, 2H), 3.12–3.02 (m, 2H), 2.59 (s, 4H), 1.40–1.12 (m, 4H); ¹³C NMR (151 MHz, CD₃OD) δ 168.16, 168.00, 156.42, 152.14, 149.96, 145.45, 143.41, 137.84, 137.64, 135.57, 133.62, 131.76, 131.47, 129.09, 128.04, 127.54, 127.48, 126.69, 44.38, 41.89, 38.84, 37.31, 32.34, 31.40; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₁N₄O₅S ([M+H]⁺) 571.2010, found 571.2008.

Synthesis of N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)-4-(hydroxymethyl)benzenesulfonamide (C-4-48). Following the procedure for the synthesis of B9 from B8, C-4-48 was prepared from 76 (0.50 g, 0.855 mmol) using LiAlH₄ (39 mg, 1.03 mmol) in dried THF (5 mL) at room temperature. Purification by column chromatography (EtOAc) gave C-4-48. White solid, 55 mg (12%). m.p. 125.4–126.7 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 8.77 (d, J = 4.5 Hz, 1H), 8.66–8.64 (m, 2H), 7.84–7.75 (m, 3H), 7.57–7.51 (m, 7H), 7.18–7.16 (m, 3H), 7.06–6.96 (m, 2H), 5.45–5.41 (m, 1H), 4.61–4.58 (m, 2H), 3.86–3.70 (m, 1H), 3.26–3.12 (m, 1.69H), 2.97 (s, 1H), 2.79–2.62 (m, 2H), 2.39–2.32 (m, 2H), 1.45–1.23 (m, 2H), 1.12–1.04 (m, 1.62H), 0.81–0.52 (m, 1H); ¹³C NMR (151 MHz, DMSO-d₆) δ 166.49, 166.32, 151.41, 151.27, 150.17, 149.87, 147.41, 145.89, 138.54, 136.84, 136.60, 135.88, 135.78, 131.55, 131.44, 130.53, 130.47, 127.82, 126.74, 126.45, 126.16, 123.67, 122.88, 122.71, 62.24, 46.78, 45.67, 42.32, 42.18, 41.42, 36.83, 36.75, 35.55, 35.50, 31.32, 30.79; ESI-HR-MS: (m/z) calcd. for C₃₁H₃₃N₄O₄S ([M+H]⁺) 557.2217, found 557.2222.

Synthesis of tert-butyl 4-(((3-aminophenyl)sulfonamido)methyl)-4-benzylpiperidine-1-carboxylate (77). Following the procedure for the synthesis of 10 from 9, 77 was prepared from 75 to 47 (2.50 g, 5.11 mmol) using 10% Pd/C (0.25 g) in MeOH (25 mL). Column chromatography (EtOAc/PE = 1/2 by v/v) gave 77. White solid, 2.04 g (87%). m.p. 159.1–160.3 °C. ¹H NMR (500 MHz, DMSO-d₆) δ 7.44 (t, J = 6.3 Hz, 1H), 7.23–7.15 (m, 4H), 7.10–7.08 (m, 2H), 6.99 (t, J = 2.0 Hz, 1H), 6.92–6.89 (m, 1H), 6.76–6.74 (m, 1H), 5.56 (s, 2H), 3.44–3.39 (m, 2H), 3.16–3.14 (m, 2H), 2.62–2.61 (m, 4H), 1.35 (s, 9H), 1.33–1.30 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (201 MHz, CDCl₃) δ 154.92, 147.56, 140.21, 136.68, 130.47, 130.13, 128.28, 126.58, 118.93, 116.32, 112.66, 79.54, 47.30, 42.27, 39.81, 38.84, 36.06, 32.18, 28.48; ESI-HR-MS: (m/z) calcd. for C₂₄H₃₃N₃NaO₄S ([M+Na]⁺) 482.2084, found 482.2084.

Synthesis of tert-butyl 4-(((3-acetamidophenyl)sulfonamido)methyl)-4-benzylpiperidine-1-carboxylate (78). Compound 78 was prepared according to General Procedure 1 from 77 (1.50 g, 5.11 mmol) using AcCl (0.31 g, 3.91 mmol) and Et₃N (0.99 g, 9.78 mmol) in dried CH₂Cl₂ (15 mL). Purification by column chromatography (EtOAc/PE = 1/1, by v/v) gave 78. White foam, 1.27 g (78%). ¹H NMR (500 MHz, DMSO-d₆) δ 10.25 (s, 1H), 8.15 (s, 1H), 7.76–7.74 (m, 1H), 7.66 (t, J = 6.5 Hz, 1H), 7.54–7.50 (m, 1H), 7.48–7.46 (m, 1H), 7.21–7.16 (m, 3H), 7.10–7.08 (m, 2H), 3.43–3.38 (m, 2H), 3.15 (s, 2H), 2.64–2.62 (m, 4H), 2.07 (s, 3H), 1.35 (s, 9H), 1.33–1.30 (m, 2H), 1.22–1.17 (m, 2H); ¹³C NMR (201 MHz, CDCl₃) δ 169.50, 155.09, 139.99, 139.51, 136.64, 130.51, 129.88, 128.37, 126.71, 124.11, 122.31, 117.88, 79.80, 47.57, 42.28, 39.88, 38.93, 36.14, 32.13, 28.53, 24.55; ESI-HR-MS: (m/z) calcd. for C₂₆H₃₅N₃NaO₅S ([M+Na]⁺) 524.2190, found 524.2190.

Synthesis of N-(3-(N-((1-([2,4′-bipyridine]-3-carbonyl)-4-benzylpiperidin-4-yl)methyl)sulfamoyl)phenyl)acetamide (C-4-49). Following General Procedure 3, 78 (1.10 g, 2.19 mmol) was first treated with TFA (5.5 mL) in CH₂Cl₂ (3.3 mL), and the intermediate obtained was reacted with 7·TFA (0.78 g, 2.63 mmol) using EDCI (1.05 g, 5.48 mmol), HOBT (22 mg, 0.164 mmol), and DIPEA (1.69 g, 13.1 mmol) in dried THF (11 mL). Purification by column chromatography (EtOAc) gave C-4-49. Pale yellow foam, 1.05 g (82%). ¹H NMR (500 MHz, DMSO-d₆) δ 10.27–10.24 (m, 1H), 8.77 (dd, J = 1.8 Hz and 4.8 Hz, 1H), 8.65–8.64 (m, 2H), 8.16 (s, 1H), 7.84–7.65 (m, 3H), 7.58–7.50 (m, 4H), 7.47–7.45 (m, 1H), 7.18–7.17 (m, 3H), 7.06–6.97 (m, 2H), 3.83–3.69 (m, 1H), 3.26–3.14 (m, 1H), 2.97 (s, 1H), 2.82–2.63 (m, 2H), 2.57–2.56 (m, 1H), 2.44–2.33 (m, 1.46H), 2.07 (s, 3H), 1.45–1.23 (m, 2H), 1.14–1.05 (m, 1.58H), 0.85–0.53 (m, 1H); ¹³C NMR (201 MHz, CDCl₃) δ 169.89, 169.43, 167.56, 167.51, 151.85, 151.32, 150.71, 150.48, 149.96, 149.39, 147.43, 146.39, 140.15, 139.85, 139.55, 139.50, 136.54, 136.22, 135.95, 131.59, 131.42, 130.53, 130.48, 130.42, 130.26, 129.75, 128.37, 128.35, 126.73, 124.27, 124.12, 124.01, 123.92, 123.61, 123.34, 121.96, 121.22, 117.79, 47.75, 46.28, 42.85, 42.81, 42.38, 40.63, 37.59, 37.52, 36.18, 35.99, 31.24, 30.95, 24.36, 24.26; ESI-HR-MS: (m/z) calcd. for C₃₂H₃₄N₅O₄S ([M+H]⁺) 584.2326, found 584.2328.

3.2. In Vitro CYP46A1 Inhibition

Chemical Materials: The chemicals used in this assay were obtained commercially: terfenadine (Sigma-Aldrich, T9652, Shanghai, China), tolbutamide (Sigma-Aldrich, T0891, Shanghai, China), buspirone (MedChemExpress, HY-B1115A, Shanghai, China), KH₂PO₄ (Shanghai Titanchem, 7778-77-0, Shanghai, China), NADPH (ACROS, 328742500, Shanghai, China), and testosterone (Adamas Reagent, 171265, Shanghai, China).

Study Procedure: Recombinant human CYP46A1R bactosomes (Cypex, 1000 nM) were incubated with testosterone (15 µM as substrate) and a series of test compounds across a seven-point concentration range (0, 0.31, 2.44, 19.5, 156, 1250, 10,000 nM) in 50 mM KH₂PO₄ buffer (pH 7.4) in a 96-deep well plate. The reaction mixture was incubated at 38 °C for 10 min after initiation with 5 mM NADPH and was then terminated with an MeCN quenching solution containing terfenadine, buspirone, and tolbutamide as internal standards. Following centrifugation, the supernatants were collected for LC-MS/MS analysis.

LC-MS/MS Conditions: The LC-MS/MS analysis was performed on an API 5500 mass spectrometer in positive ESI mode with unit resolution for both Q1 and Q3. Chromatographic separation used a Kinetex Polar C₁₈ column (2.6 μm, 2.1 × 50 mm) with a 3 min gradient at a flow rate of 0.7 mL/min, where mobile phase A was 0.1% formic acid in water and mobile phase B was 0.1% formic acid in acetonitrile. Key monitored multiple reaction monitoring (MRM) transitions included terfenadine (472.4/436.4), tolbutamide (271.025/91), 16β-hydroxytestosterone (305.203/97.1 and 305.203/109.2), and buspirone (386.2/122).

Calculation: The enzyme activity for each concentration was calculated as the percentage of the substrate metabolite peak area ratio at a given concentration (0, 0.31, 2.44, 19.5, 156, 1250, 10,000 nM) relative to the peak area ratio at the zero-concentration control (0 nM). Correspondingly, the inhibition percentage was derived as follows: Inhibition (%) = 100% − Enzyme Activity (%). The half-maximal inhibitory concentration (IC₅₀) values were subsequently determined by analyzing the concentration–response curve using nonlinear regression in GraphPad Prism software (version 5.03, GraphPad Software, Inc., Boston, MA, USA).

3.3. In Vitro Inhibitory Activities of Target Compounds Against CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4

Chemical Materials: The study utilized pooled mixed-gender human liver microsomes (Corning, 452117, Suzhou, China). A panel of chemical inhibitors and substrates for specific CYP isoforms was obtained commercially from various vendors: terfenadine (Sigma-Aldrich, T9652, Shanghai, China), tolbutamide (Sigma-Aldrich, T0891, Shanghai, China), buspirone (MedChemExpress, HY-B1115A, Shanghai, China), phenacetin (Sigma-Aldrich, 101690303, Shanghai, China), diclofenac (MCE, HY-15036, Shanghai, China), mephenytoin (Glpbio, GC14486, Shanghai, China), dextromethorphan (Sigma-Aldrich, D9684-5G, Shanghai, China), midazolam (Shanghai yuanye Bio-Technology, PVJT-0H9Z, Shanghai, China), K₂HPO₄ (SCR, 20032117, Shanghai, Chinna), and NADPH (ABCONE, N99640-100MG, Shanghai, China).

Study Procedure: The incubation was automated on a TECAN Fluent 780 workstation. A liver microsome working solution containing a 5-in-1 substrate cocktail (phenacetin, diclofenac, mephenytoin, dextromethorphan, and midazolam) was pre-incubated at 38 °C for 7 min. Test compounds were then added at six non-zero concentrations (0, 0.049, 0.20, 0.78, 3.1, 12.5, 50 µM). The reaction was initiated with 5 mM NADPH and incubated at 38 °C for 10 min before termination with an MeCN quenching solution containing terfenadine, tolbutamide, and buspirone as internal standards. Following centrifugation, the supernatants were collected for LC-MS/MS analysis.

LC-MS/MS Conditions: Analysis was performed on an AB Sciex API 5500 mass spectrometer (AB SCIEX, Singapore) in positive ESI mode. Chromatographic separation used a Kinetex Polar C₁₈ column (2.6 μm, 2.1 × 50 mm, Phenomenex, Torrance, CA, USA) with a 2.5 min gradient of 0.1% formic acid in water (mobile phase A) and 0.1% formic acid in acetonitrile (mobile phase B) at a flow rate of 0.7 mL/min. Analytes were monitored via specific MRM transitions: acetaminophen (metabolite of phenacetin; 152.1/110.0), 4′-hydroxydiclofenac (metabolite of diclofenac; 312.1/230.0), 4′-hydroxymephenytoin (metabolite of mephenytoin; 235.0/150.0), dextrorphan (metabolite of dextromethorphan; 258.2/199.1), and 1′-hydroxymidazolam (metabolite of midazolam; 342.1/203.0).

Calculation: The enzyme activity for each compound concentration was calculated as the percentage of the substrate metabolite peak area ratio at a given concentration (0, 0.049, 0.20, 0.78, 3.1, 12.5, 50 µM) relative to the peak area ratio at the zero-concentration control (0 nM). Correspondingly, the inhibition percentage was derived as follows: Inhibition (%) = 100% − Enzyme Activity (%). The half-maximal inhibitory concentration (IC₅₀) values were subsequently determined by analyzing the concentration–response curve using nonlinear regression in GraphPad Prism software (version 5.03, GraphPad Software, Inc., Boston, MA, USA).

4. Conclusions

In conclusion, three series of soticlestat derivatives were designed and evaluated for their in vitro CYP46A1 inhibitory activity. Among the designed series, Series A, B, and subseries C-1 to C-3 were associated with significantly decreased CYP46A1 inhibitory activity, while a lot of compounds with benzenesulfonamide moiety (subseries C-4) as an isostere of OH in soticlestat were discovered to possess CYP46A1 inhibitory activities comparable to that of soticlestat. The most potent compound was C-4-38, with an IC₅₀ of 13.6 nM, compared with an IC₅₀ of 18.0 nM for soticlestat. An interesting flat SAR profile was also observed in some compounds in subseries C-4. Although four selected compounds displayed low selectivity toward CYP3A4/5 inhibition, which will be optimized in future work to minimize potential drug–drug interactions, the findings in the present study still remain very valuable for the design of potent CYP46A1 inhibitors.

Acknowledgments

The authors are grateful to the assistance from Yanlan Qin for the collection of ESI-HR-MS data.

Abbreviations

The following abbreviations are used in this manuscript:

AD	Alzheimer’s disease
BBB	blood–brain barrier
CH24H	cholesterol 24-hydroxylase
dba	dibenzylideneacetone
DEE	developmental and epileptic encephalopathy
DME	1,2-dimethoxyethane
DMF	N,N-dimethylformamide
DS	Dravet syndrome
EAAT2	excitatory amino acid transporter 2
EDCI	1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride
ESI	electrospray ionization
HOBT	1-hydroxybenzotriazole
HR-MS	high-resolution mass spectrometry
HTD	Huntington’s disease
IC₅₀	Half-maximal inhibitory concentration
LDA	lithium diisopropylamide
LGS	Lennox–Gastaut syndrome
LiHMDS	lithium bis(trimethylsilyl)amide
mCPBA	m-chloroperoxybenzoic acid
NMDA	N-methyl-D-aspartate
PD	Parkinson’s disease
PE	petroleum ether
PIFA	phenyliodine (III) bis(trifluoroacetate)
TBAF	tetra-n-butylammonium fluoride
TFA	trifluoroacetic acid
TLC	thin-layer chromatography
TMS	trimethylsilyl
Xantphos	9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene

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Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/molecules31030460/s1, the copies of all the ¹H NMR, ¹³C NMR, ¹⁹F NMR, ³¹P NMR, and HR-MS spectra of synthesized intermediates and target compounds.

molecules-31-00460-s001.zip^{(34MB, zip)}

Author Contributions

Conceptualization, J.W. and G.Z.; methodology, X.H., W.H., J.W. and G.Z.; formal analysis, X.H., W.H., J.W. and G.Z.; investigation, X.H., W.H., X.L., H.Z., Y.H., J.W. and G.Z.; resources, G.Z.; data curation, X.H., W.H. and G.Z.; writing—original draft preparation, X.H., W.H. and G.Z.; writing—review and editing, J.W. and G.Z.; supervision, J.W. and G.Z.; project administration, G.Z.; funding acquisition, G.Z. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

Funding Statement

This research was funded by the Special Funds of National Natural Science Foundation of China, grant number 82441046, the Zhongshan Municipal Natural Science Foundation, grant number 2023B2019, and the Creative Research Group of Zhongshan City (Lingnan Pharmaceutical Research and Innovation team), grant number CXTD2022011.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

References

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

molecules-31-00460-s001.zip^{(34MB, zip)}

Data Availability Statement

The data presented in this study are available on request from the corresponding authors.

[B1-molecules-31-00460] 1.Asadi-Pooya A.A. Lennox-Gastaut syndrome: A comprehensive review. Neurol. Sci. 2018;39:403–414. doi: 10.1007/s10072-017-3188-y. [DOI] [PubMed] [Google Scholar]

[B2-molecules-31-00460] 2.Sullivan J., Benítez A., Roth J., Andrews J.S., Shah D., Butcher E., Jones A., Cross J.H. A systematic literature review on the global epidemiology of Dravet syndrome and Lennox-Gastaut syndrome: Prevalence, incidence, diagnosis, and mortality. Epilepsia. 2024;65:1240–1263. doi: 10.1111/epi.17866. [DOI] [PubMed] [Google Scholar]

[B3-molecules-31-00460] 3.Vasquez A., Wirrell E.C. Prevalence, healthcare resource utilization and mortality of Lennox-Gastaut syndrome: Retrospective linkage cohort study. Seizure-Eur. J. Epilep. 2021;91:159–166. doi: 10.1016/j.seizure.2021.05.025. [DOI] [PubMed] [Google Scholar]

[B4-molecules-31-00460] 4.Vasquez A., Wirrell E.C. State-of-the-art management of Dravet syndrome. Dev. Med. Child. Neurol. 2025;67:1527–1535. doi: 10.1111/dmcn.16475. [DOI] [PubMed] [Google Scholar]

[B5-molecules-31-00460] 5.Zhu Z., Zhang Z., Xiao W., Wang C., Liang R. Efficacy and safety of pharmacological and non-pharmacological therapies in Lennox-Gastaut syndrome: A systematic review and network meta-analysis. Front. Pharmacol. 2025;16:1522543. doi: 10.3389/fphar.2025.1522543. [DOI] [PMC free article] [PubMed] [Google Scholar]

[B6-molecules-31-00460] 6.Samanta D., Nath M. Current and emerging pharmacotherapies in Lennox-Gastaut syndrome. Expert Opin. Pharmacother. 2025;26:1133–1147. doi: 10.1080/14656566.2025.2516630. [DOI] [PubMed] [Google Scholar]

[B7-molecules-31-00460] 7.Moutinho M., Nunes M.J., Rodrigues E. Cholesterol 24-hydroxylase: Brain cholesterol metabolism and beyond. Biochim. Biophys. Acta. 2016;1861:1911–1920. doi: 10.1016/j.bbalip.2016.09.011. [DOI] [PubMed] [Google Scholar]

[B8-molecules-31-00460] 8.Alavi M.S., Karimi G., Ghanimi H.A., Roohbakhsh A. The potential of CYP46A1 as a novel therapeutic target for neurological disorders: An updated review of mechanisms. Eur. J. Pharmacol. 2023;949:175726. doi: 10.1016/j.ejphar.2023.175726. [DOI] [PubMed] [Google Scholar]

[B9-molecules-31-00460] 9.Pikuleva I.A., Cartier N. Cholesterol hydroxylating cytochrome P450 46A1: From mechanisms of action to clinical applications. Front. Aging Neurosci. 2021;13:696778. doi: 10.3389/fnagi.2021.696778. [DOI] [PMC free article] [PubMed] [Google Scholar]

[B10-molecules-31-00460] 10.Petrov A.M., Pikuleva I.A. Cholesterol 24-hydroxylation by CYP46A1: Benefits of modulation for brain diseases. Neurotherapeutics. 2019;16:635–648. doi: 10.1007/s13311-019-00731-6. [DOI] [PMC free article] [PubMed] [Google Scholar]

[B11-molecules-31-00460] 11.Tian G., Kong Q., Lai L., Ray-Chaudhury A., Lin C.-L.G. Increased expression of cholesterol 24S-hydroxylase results in disruption of glial glutamate transporter EAAT2 association with lipid rafts: A potential role in Alzheimer’s disease. J. Neurochem. 2010;113:978–989. doi: 10.1111/j.1471-4159.2010.06661.x. [DOI] [PMC free article] [PubMed] [Google Scholar]

[B12-molecules-31-00460] 12.Paul S.M., Doherty J.J., Robichaud A.J., Belfort G.M., Chow B.Y., Hammond R.S., Crawford D.C., Linsenbardt A.J., Shu H.J., Izumi Y., et al. The major brain cholesterol metabolite 24(S)-hydroxycholesterol is a potent allosteric modulator of N-methyl-D-aspartate receptors. J. Neurosci. 2013;33:17290–17300. doi: 10.1523/JNEUROSCI.2619-13.2013. [DOI] [PMC free article] [PubMed] [Google Scholar]

[B13-molecules-31-00460] 13.Koike T., Yoshikawa M., Ando H.K., Farnaby W., Nishi T., Watanabe E., Yano J., Miyamoto M., Kondo S., Ishii T., et al. Discovery of soticlestat, a potent and selective inhibitor for cholesterol 24-hydroxylase (CH24H) J. Med. Chem. 2021;64:12228–12244. doi: 10.1021/acs.jmedchem.1c00864. [DOI] [PubMed] [Google Scholar]

[B14-molecules-31-00460] 14.Zhang L., Jiang N., Wang C. Efficacy, safety, and tolerability of soticlestat (TAK-935) as adjunctive therapy in pediatric patients with dravet syndrome and Lennox-Gastaut syndrome: A meta-analysis of 3 randomized controlled trials. Front. Pharmacol. 2025;16:1586098. doi: 10.3389/fphar.2025.1586098. [DOI] [PMC free article] [PubMed] [Google Scholar]

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PERMALINK

Structure–Activity Relationship Study on Soticlestat Derivatives for the Discovery of CYP46A1 (CH24H) Inhibitors

Xinwei Hu

Wenqian Huang

Xiaotong Lin

Hao Zhang

Yishu Huang

Jiang Wu

Guilong Zhao

Roles

Abstract

1. Introduction

Figure 1.

2. Results and Discussion

2.1. Chemistry

Scheme 1.

Scheme 2.

Scheme 3.

Scheme 4.

Scheme 5.

Scheme 6.

Scheme 7.

Scheme 8.

Scheme 9.

Scheme 10.

Scheme 11.

Scheme 12.

Scheme 13.

Scheme 14.

Scheme 15.

Scheme 16.

Scheme 17.

2.2. In Vitro CYP46A1 Inhibition

Table 1.

2.3. In Vitro Inhibitory Activities of Target Compounds Against CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4

Table 2.

3. Materials and Methods

3.1. Chemistry

3.2. In Vitro CYP46A1 Inhibition

3.3. In Vitro Inhibitory Activities of Target Compounds Against CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4

4. Conclusions

Acknowledgments

Abbreviations

Supplementary Materials

Author Contributions

Institutional Review Board Statement

Informed Consent Statement

Data Availability Statement

Conflicts of Interest

Funding Statement

Footnotes

References

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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