New 1,2,3-Triazole-genipin Analogues and Their Anti-Alzheimer’s Activity

Patamawadee Silalai; Suwichada Jaipea; Jiraporn Tocharus; Anan Athipornchai; Apichart Suksamrarn; Rungnapha Saeeng

doi:10.1021/acsomega.2c01593

. 2022 Jul 6;7(28):24302–24316. doi: 10.1021/acsomega.2c01593

New 1,2,3-Triazole-genipin Analogues and Their Anti-Alzheimer’s Activity

Patamawadee Silalai ^†, Suwichada Jaipea ^†, Jiraporn Tocharus ^‡, Anan Athipornchai ^†, Apichart Suksamrarn ^§, Rungnapha Saeeng ^†,^∥,^*

PMCID: PMC9301951 PMID: 35874205

Abstract

graphic file with name ao2c01593_0012.jpg

A novel series of 1,2,3-triazole-genipin analogues were designed, synthesized, and evaluated for neuroprotective activity, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) inhibitory activity. The genipin analogues bearing bromoethyl- and diphenylhydroxy-triazole showed in vitro neuroprotective properties against H₂O₂ toxicity along with potent inhibitory activity on BuChE with IC₅₀ values of 31.77 and 54.33 μM, respectively, compared with galantamine (IC₅₀ = 34.05 μM). The molecular docking studies of these genipin analogues showed good binding energy and interact well with the key amino acids of BuChE via hydrogen-bonding and hydrophobic interactions. Triazole genipins might be promising lead compounds as anti-Alzheimer’s agents.

1. Introduction

Alzheimer’s disease (AD) is the most common form of neurodegenerative disorder and the most prevalent cause of dementia, making it one of the major public health problems.¹ A report by the World Health Organization (WHO) showed that about 50 million people are affected by dementia worldwide, and it is projected to affect around 115.4 million people worldwide by 2050.² Nowadays, four common drugs for the treatment of Alzheimer’s disease have been approved by the European and United States regulatory authorities including tacrine,³ memantine,⁴ galantamine,⁵ and donepezil⁶ (Figure 1). The therapeutic drugs on the market are not widely available since their efficacy is limited by diverse unpleasant side effects. Thus, there is an urgent need for the development of effective anti-Alzheimer’s agents with low side effects.

Examples of drugs used for Alzheimer’s disease (AD) available on the market.

AD is a multifactorial disease commonly featuring neuronal cell death and loss of cholinergic neurons due to a decrease in acetylcholine availability at neuronal synapses.⁷ From a physiological point of view, the activity of acetylcholine in the synapses can be diminished by the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE).⁸ Therefore, one efficient approach to cure AD is to restore the level of acetylcholine using AChE and BuChE inhibitors.⁹ In normal healthy brains, AChE plays an important role and BuChE is supportive in the hydrolysis of acetylcholine.¹⁰ As AD progresses, the level of AChE in the brain declines by approximately 50% of normal values whereas BuChE progressively increases to 120% of normal levels. Thus, the BuChE activity progressively increases as the graveness of dementia increases but AChE activity diminishes. Therefore, BuChE was examined as a key target for the treatment of AD.^11,12 Hence, BuChE inhibitors with neuroprotection potential may have a special therapeutic effect on AD.^13,14

Gardenia jasminoides Ellis is a flowering plant belonging to the gardenia genus in the Rubiaceae family. The fruits are used as a therapeutic herb that is rich in biological activity, such as inflammation, jaundice, and hepatic disorders.¹⁵ Generally, this herb is used in herbal medicines or functional food supplements displaying therapeutic effects on central nervous system (CNS) diseases, including dementia, cerebral stroke, and antioxidants with nonharmful and nontoxic side effects.¹⁶ Geniposide, the main component in the fruit, belongs to the class of iridoid glycoside and can be hydrolyzed into genipin 1 by intestinal bacteria after ingestion (Figure 2).¹⁷

Chemical structures of geniposide, genipin 1, and derivatives.

Pharmacokinetic studies have suggested that genipin is the main active compound and showed promising bioactivities as a strong neuroprotection agent by inhibiting high-level lactate dehydrogenase (LDH) in the blood, which causes amyloid-β (Aβ) peptide toxicity in cultured neuronal cells.¹⁸ Recently, Huang et al.¹⁹ reported that piperazine-genipin analogues are dual AChE/Aβ_1–42 aggregation inhibitors, which repair the neuronal cell damage from amyloid-β (Aβ) peptide toxicity by 22.3% (Figure 2). These results led us to design and modify the structure of genipin to explore the potential of its derivatives as candidates for the treatment of AD.

1,2,3-Triazole is a five-membered heterocyclic compound containing two carbon and three nitrogen atoms. 1,2,3-Triazole is found in abundance in medicinal compounds.^20,21 The triazole ring displays bond acceptor properties capable of forming significant interactions with biomolecular targets through H-bonding, π–π stacking, and dipole interactions. These scaffolds are commonly synthesized through Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition between alkynes and azides (CuAAC) by the concept of click.²²⁻²⁶ Previously, some triazole derivatives were synthesized as potent and highly selective BuChE inhibitors and neuroprotective agents (Figure 3).²⁷⁻³⁰

Some examples of 1,2,3-triazole used as inhibitors of butyrylcholinesterase (BuChE) and neuroprotective agents.

Considering the work on genipin and 1,2,3-triazole mentioned above, the linking of these two units might lead to hybrids with higher neuroprotective activity than the parent genipin. Therefore, in this work, a new series of 1,2,3-triazole-genipin analogues were designed and synthesized and were focused on the biological evaluation as selective BuChE inhibitors with neuroprotective properties. The molecular docking studies were also explored for further understanding of enzyme inhibition (Figure 4).

Design of novel 1,2,3-triazole-genipin analogues.

2. Results and Discussion

2.1. Chemistry

The synthetic route for modification of genipin to 1,2,3-triazole-genipin analogues 8a and 8b is depicted in Scheme 1. The target compounds were synthesized via six- or seven-step reactions. Initially, genipin 1 was silylated to protect the hydroxy at C-10 by stirring in tert-butyldimethylsilyl chloride (TBSCl) in pyridine for 10 min to obtain 2. Compound 2 was further reacted with imidazole and acetic anhydride (Ac₂O) or tert-butyldiphenylsilyl chloride (TBDPSCl) for conversion of the hydroxy of the hemiacetal to acetyl or silyl ether giving compounds 3a or 3b, respectively. Subsequently, deprotection of tert-butyldimethylsilyl (TBS)-ether at the C-10 position of genipin was achieved by dropwise addition of HCOOH/H₂O (9:1) at 0 °C and stirring for 6 h to obtain a crude product 4a or 4b. Mesylation of the resulting hydroxy group afforded the corresponding mesyl derivatives. No further chromatography purification was necessary for the four steps. Azidation of mesylate group to desired azido precursor 6a yielded 72% in five steps. Desilylation of the TBDPS group at C-1 of 6b was carried out using tetra-n-butylammonium fluoride (TBAF) to obtain the hemiacetal analogue 7b in 43% yield in six steps. The azide–alkyne Huisgen cycloaddition reaction was performed in the final step by mixing 6a or 7b with various alkynes using copper iodide to promote reaction to give a series of C-10 triazole analogues 8a or 8b.

As shown in Scheme 2, the reactions of different alkynes with azido genipin 6a and 7b were explored. Genipin analogues 8a and 8b bearing phenyl, benzyl ether, benzylamine, and aliphatic, phthalimide, and alicyclic substituted triazoles with different carbon chain lengths were successfully obtained in good to excellent yields. It was observed that phenyl-substituted, benzyl ether, and benzylamine afforded the corresponding products (8a-1–8a-8) in moderate to excellent yields (52–99%). Different substituents on the aromatic ring (−OCH₃, −F) in compounds 8a-2 and 8a-3 did not affect the yields in this transformation. A series of aliphatic chains bearing bromine 8a-9, hydroxy group 8a-10 and 8a-11, silyl group (8a-12–8a-15), trityl 8a-16, and long-chain aliphatic chains (8a-17–8a-19) were reacted smoothly, affording the desired products in good to excellent yields (66–92%). Moreover, the reaction proceeded in good to excellent yields with alkynyl-phthalimides and hydroxy alicyclic alkyne (8a-20–8a-26).

For a series of hemiacetal triazole genipin analogues 8b, phenyl-substituted with the electron-withdrawing group fluorine 8b-3 were more favorable for conversions than the electron-donating group methoxy 8b-2. Triazoles bearing diphenyl or aliphatic chains provided the desired genipin analogues (8b-4–8b-6) in 46–78% yields. Additionally, the reaction of the long-chain aliphatic substituted triazole delivered the corresponding products (8b-7–8b-9) in moderate yields. The triazole substituted with phthalimide gave products 8b-10 and 8b-11 in 68 and 80% yields, respectively.

Finally, hydroxy alicyclic reacted smoothly to furnish corresponding triazole products 8b-12 and 8b-13 in excellent yields.

Based on the above experimental results, the hemiacetal products 8b gave products with lower yields and stability than acetoxy-substituted analogues 8a.

2.2. Biological Evaluations

2.2.1. Neuroprotective Effects of 1,2,3-Triazole-genipin Analogues on the H₂O₂ Induced Decrease in Cell Viability

The protective effect of 1,2,3-triazole-genipin analogues on the H₂O₂-induced cell viability was studied. As shown in Table 1, 250 μM H₂O₂ significantly reduced cell viability (43.0 ± 0.9%). During treatment with our synthetic compounds, 14 analogues exhibited significant neuroprotective activity with a level up to 70% of cell viability at 0.075 μM and some analogues showed better activity than the parent genipin 1 (78.0%). In the series of acetoxy analogues 8a, compound 8a-2 with substituted p-methoxy and 8a-3 with p-fluoro substituent on aryltriazole exhibited neuroprotective activity with 72.5 and 70.9% cell viability at 0.075 μM, respectively. Both the electron-withdrawing and electron-donating groups on aryltriazole showed similar results. Triazole genipin analogue 8a-5 with benzyl ether (79.7% of cell viability) and 3,4-OCH₃8a-7 (78.1% of cell viability) showed better cell viabilities than the analogues 4-OCH₃8a-6 (62.7% of cell viability) and benzylamine 8a-8 (50.8% of cell viability). When the benzyl ether substituent (8a-5–8a-8) was replaced by an alkyl chain (8a-9–8a-19), the neuroprotective activity was significantly increased. Substituents such as Br and OH aryltriazoles on compounds 8a-10, 8a-11, and 8a-14 showed superior neuroprotective activity, while compounds 8a-20–8a-24 containing substituted phthalimide displayed moderate neuroprotective activity. The exception was 8a-20, which showed remarkable cell viability of up to 78.5% at 0.075 μM. Furthermore, hydroxy-hexacyclic compound 8a-26 showed better activity than the pentacyclic compound 8a-25 at 0.075 μM, which indicated the effect of substituted groups on the neuroprotective activity.

Table 1. Neuroprotective Effects of 1,2,3-Triazole-genipin Analogues.

cell viability (%)^a/recovery of cell viability (%)^b
compounds	0.075 μM	0.15 μM	0.3 μM	0.6 μM
control	100
H₂O₂ (250 μM)	43.0 ± 0.9
genipin 1	78.0 ± 0.5 (35.0)	71.4 ± 0.5 (28.4)	57.8 ± 0.7 (14.8)	64.4 ± 0.5 (21.4)
8a-1	NA^c	NA^c	NA^c	NA^c
8a-2	72.5 ± 0.6 (29.5)	66.6 ± 0.7 (23.6)	60.1 ± 1.0 (17.1)	54.2 ± 0.8 (11.2)
8a-3	70.9 ± 1.5 (27.9)	64.9 ± 1.2 (21.9)	58.6 ± 0.9 (15.6)	52.3 ± 0.9 (9.3)
8a-4	NA^c	NA^c	NA^c	NA^c
8a-5	79.7 ± 0.4 (36.7)	73.0 ± 0.2 (30.0)	67.1 ± 0.2 (24.1)	60.6 ± 0.4 (17.6)
8a-6	62.7 ± 0.3 (19.7)	65.9 ± 0.7 (22.9)	67.6 ± 0.5 (24.6)	69.5 ± 0.2 (26.5)
8a-7	78.1 ± 0.4 (35.1)	71.7 ± 0.06 (28.7)	65.3 ± 0.21 (22.3)	59.0 ± 0.21 (16.0)
8a-8	50.8 ± 0.9 (7.8)	50.8 ± 0.6 (7.8)	52.9 ± 0.5 (9.9)	51.2 ± 0.8 (8.2)
8a-9	NA^c	NA^c	NA^c	NA^c
8a-10	80.9 ± 0.4 (37.9)^d	74.8 ± 0.6 (31.8)	68.9 ± 0.5 (25.9)	61.9 ± 0.2 (18.9)
8a-11	83.5 ± 2.5 (40.5)^d	77.1 ± 2.1 (34.1)	71.2 ± 2.8 (28.2)	65.3 ± 0.29 (22.3)
8a-12	49.6 ± 0.6 (6.6)	48.5 ± 0.8 (5.5)	47.8 ± 0.3 (4.8)	53.2 ± 0.5 (10.2)
8a-13	74.2 ± 0.4 (31.2)	68.6 ± 0.15 (25.6)	62.8 ± 0.2 (19.8)	56.6 ± 0.2 (13.6)
8a-14	78.8 ± 0.4 (35.8)	72.7 ± 0.4 (29.7)	66.6 ± 0.1 (23.6)	60.8 ± 0.8 (17.8)
8a-15	NA^c	NA^c	NA^c	NA^c
8a-16	NA^c	NA^c	NA^c	NA^c
8a-17	56.1 ± 0.5 (13.1)	62.5 ± 0.4 (19.5)	68.1 ± 0.1 (25.1)	74.4 ± 0.6 (31.4)
8a-18	52.1 ± 0.5 (9.1)	58.2 ± 0.3 (15.2)	60.8 ± 0.6 (17.8)	61.2 ± 0.8 (18.2)
8a-19	57.1 ± 0.3 (14.1)	63.2 ± 0.3 (20.2)	69.2 ± 0.4 (26.2)	75.3 ± 0.5 (32.3)
8a-20	78.5 ± 0.4 (35.5)	71.6 ± 0.1 (28.6)	66.4 ± 0.1 (23.4)	60.1 ± 0.1 (17.1)
8a-21	53.5 ± 0.6 (10.5)	54.2 ± 1.1 (11.2)	56.8 ± 1.3 (13.8)	58.2 ± 1.7 (15.2)
8a-22	53.2 ± 2.5 (10.2)	54.9 ± 2.7 (11.9)	60.8 ± 1.6 (17.8)	65.5 ± 2.7 (22.5)
8a-23	50.9 ± 0.4 (7.9)	52.9 ± 0.7 (9.9)	61.6 ± 0.5 (18.6)	66.1 ± 0.8 (23.1)
8a-24	50.7 ± 0.5 (7.7)	51.7 ± 0.7 (8.7)	60.5 ± 0.7 (17.5)	65.9 ± 1.1 (22.9)
8a-25	52.3 ± 0.8 (9.3)	58.1 ± 1.1 (15.1)	60.2 ± 1.2 (17.2)	63.4 ± 0.2 (20.4)
8a-26	75.1 ± 0.9 (32.1)	69.2 ± 1.1 (26.2)	63.3 ± 1.0 (20.3)	57.1 ± 1.2 (14.1)
8b-1	NA^c	NA^c	NA^c	NA^c
8b-2	54.9 ± 2.5 (11.9)	63.0 ± 2.6 (20.0)	75.2 ± 2.3 (32.2)	78.6 ± 1.9 (35.6)
8b-3	50.9 ± 1.2 (7.9)	52.6 ± 1.6 (9.6)	55.9 ± 1.1 (12.9)	59.9 ± 0.7 (16.9)
8b-4	73.0 ± 3.1 (30.0)	80.9 ± 3.0 (37.9)^d	72.7 ± 2.6 (29.7)	69.2 ± 1.7 (26.2)
8b-5	NA^c	NA^c	NA^c	NA^c
8b-6	NA^c	NA^c	NA^c	NA^c
8b-7	51.6 ± 1.4 (8.6)	53.2 ± 1.7 (10.2)	53.7 ± 2.5 (10.7)	65.9 ± 1.1 (22.9)
8b-8	52.1 ± 0.5 (9.1)	58.2 ± 0.3 (15.2)	60.8 ± 0.6 (17.8)	61.2 ± 0.8 (18.2)
8b-9	NA^c	NA^c	NA^c	NA^c
8b-10	52.0 ± 1.8 (9.0)	70.9 ± 1.3 (27.9)	73.6 ± 1.6 (30.6)	77.2 ± 1.8 (34.2)
8b-11	70.1 ± 1.5 (27.1)	72.7 ± 1.5 (29.7)	75.5 ± 0.1 (32.5)	72.2 ± 0.9 (29.2)
8b-12	75.0 ± 2.5 (32.0)	78.3 ± 1.8 (35.3)	78.2 ± 0.9 (35.2)	77.2 ± 0.9 (34.2)
8b-13	72.5 ± 2.5 (29.5)	79.9 ± 0.5 (36.9)	79.2 ± 1.0 (36.2)	74.1 ± 1.7 (31.1)

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Cell viability (%): the cell viability in control was taken as 100%; all data were expressed as mean ± standard deviation (SD) (n = 3).

Recovery of cell viability (%): the difference value between the cell viability of compound-treated cells and that of H₂O₂-treated cells.

NA: not active.

Bold values highlight the most potent activity.

For the series of hemiacetal triazole genipin analogues 8b, compounds bearing electron-donating 4-OCH₃ aryl (compound 8b-2, 78.6%) exhibited remarkably higher neuroprotective activity than the electron-withdrawing p-fluoroaryl (compound 8b-3, 59.9%) at the same concentration of 0.6 μM. When the concentration was reduced to 0.075–0.3 μM, the cell viability decreased. The activity results of 8a-2 and 8b-2 demonstrated that a substituted group at the C-1 position showed a significant difference between the neuroprotective potencies. In addition, at a concentration of 0.15 μM, compound 8b-4 exhibited significant neuroprotective effects and the cell viability was up to 80.9%. When the concentration was reduced to 0.075 μM, the cell viability decreased to 73.0%. Therefore, a concentration of 0.15 μM was suitable for treatment by the synthetic compounds. For the replacement of long-chain aliphatic ether groups on triazole with different carbon chain lengths, both 8b-7 and 8b-8 decreased the cell viability compared with an aromatic substituted triazole (8b-2 and 8b-4). On replacing alkyl with phthalimide, compounds 8b-10 and 8b-11 exhibited strong neuroprotective activities of 77.2 and 75.5%, respectively. Moreover, compounds 8b-12 and 8b-13 bearing a hydroxyl cyclic group increased cell viability with percentages of 79.9 and 77.3%, respectively, at 0.15 μM, which might be due to its favorable conformation that allows these scaffolds to fit within the active site of the enzyme.

The overall results indicated that some 1,2,3-triazole-genipin analogues (8a-5, 8a-7, 8a-10, 8a-11, 8a-14, 8a-20, 8b-2, 8b-4, 8b-12, and 8b-13) at concentrations of 0.075–0.6 μM significantly improved the cell viability rate of H₂O₂-treated neuronal cells by up to 78% (Figure 5). Compound 8a-11 showed the highest protective capability (83.5% of cell viability) at 0.075 μM recovering the neuronal cell damage from H₂O₂ toxicity with 40.5%. Compounds 8a-10 and 8b-4 displayed similar protective ability (80.9% of cell viability) recovering the neuronal cell damage by H₂O₂ toxicity with 37.9%. These three analogues evidenced the most significant protection in reducing H₂O₂-induced neurotoxicity in neuroblastoma cells.

Neuroprotective effect of 1,2,3-triazole-genipin analogues on survival of H₂O₂-treated neurons, Compounds 1, **8a-5**, **8a-7**, **8a-10**, **8a-11**, **8a-14**, **8a-20**, **8b-2**, **8b-4**, **8b-12**, and **8b-13** significantly exhibited the neuroprotective effect with >78% cell viability.

2.2.2. Cholinesterase Inhibition Assay

The inhibitory activity of the newly synthesized 1,2,3-triazole-genipin analogues (8a and 8b) was evaluated against electric eel-derived AChE (eeAChE) and equine serum-derived BuChE (eqBuChE)³¹ and compared with galantamine, a reference drug with IC₅₀ values 12.7 and 34 μM, respectively. As shown in Table 2, the results of inhibitory activity for butyrylcholinesterase (BuChE) were superior to acetylcholinesterase (AChE). All synthetic analogues demonstrated inhibition of AChE less than 50%, and hence further IC₅₀ measurement was not carried out. Almost all synthesized compounds gave higher inhibitory activities against BuChE than the natural product geniposide and genipin 1 indicating that the introduction of the triazole ring greatly influenced the inhibitory behavior of genipin.

Table 2. ChE Inhibitory Activity of 1,2,3-Triazole-genipin Analogues^a.

	AChE inhibitory activity		BuChE inhibitory activity
compounds	inhibition (%)^b	IC₅₀ (μM ± SD)^b	inhibition (%)^b	IC₅₀ (μM ± SD)^b
geniposide	0.73 ± 0.11	NA^c	2.09 ± 0.18	NA^c
genipin 1	4.94 ± 0.05	NA^c	2.42 ± 0.18	NA^c
8a-1	1.31 ± 0.08	NA^c	47.75 ± 0.29	NA^c
8a-2	9.28 ± 0.14	NA^c	34.97 ± 0.26	NA^c
8a-3	7.89 ± 0.05	NA^c	33.37 ± 0.18	NA^c
8a-4	20.89 ± 0.22	NA^c	27.14 ± 0.09	NA^c
8a-5	0.30 ± 0.31	NA^c	39.26 ± 0.18	NA^c
8a-6	6.03 ± 0.15	NA^c	42.91 ± 0.20	NA^c
8a-7	20.35 ± 0.06	NA^c	35.99 ± 0.29	NA^c
8a-8	36.60 ± 0.42	NA^c	41.96 ± 0.12	NA^c
8a-9	9.39 ± 0.11	NA^c	1.21 ± 0.18	NA^c
8a-10	9.27 ± 0.19	NA^c	97.34 ± 0.18	31.77 ± 0.17
8a-11	0.26 ± 0.15	NA^c	35.48 ± 0.59	NA^c
8a-12	1.16 ± 0.14	NA^c	1.79 ± 0.17	NA^c
8a-13	0.43 ± 0.19	NA^c	9.03 ± 0.30	NA^c
8a-14	1.33 ± 0.08	NA^c	27.54 ± 0.20	NA^c
8a-15	0.28 ± 0.21	NA^c	22.32 ± 0.52	NA^c
8a-16	8.00 ± 0.79	NA^c	10.70 ± 0.15	NA^c
8a-17	8.12 ± 0.22	NA^c	37.35 ± 0.61	NA^c
8a-18	12.11 ± 0.30	NA^c	23.68 ± 0.17	NA^c
8a-19	44.70 ± 0.19	NA^c	25.56 ± 0.05	NA^c
8a-20	5.52 ± 0.32	NA^c	27.29 ± 0.17	NA^c
8a-21	6.62 ± 0.36	NA^c	78.64 ± 0.10	274 ± 3.9
8a-22	19.46 ± 0.20	NA^c	99.85 ± 0.13	203 ± 1.7
8a-23	0.13 ± 0.29	NA^c	71.55 ± 0.22	419 ± 4.4
8a-24	0.88 ± 0.30	NA^c	47.55 ± 0.13	NA^c
8a-25	0.62 ± 0.24	NA^c	40.70 ± 0.23	NA^c
8a-26	0.48 ± 0.17	NA^c	42.73 ± 0.18	NA^c
8b-1	8.19 ± 0.11	NA^c	67.51 ± 0.16	537 ± 2.0
8b-2	4.41 ± 0.03	NA^c	98.69 ± 0.24	109.1 ± 0.61
8b-3	7.53 ± 0.18	NA^c	84.64 ± 0.12	281 ± 2.7
8b-4	11.11 ± 0.88	NA^c	99.72 ± 0.18	54.3 ± 0.34
8b-5	2.30 ± 0.14	NA^c	24.94 ± 0.23	NA^c
8b-6	16.44 ± 0.25	NA^c	35.42 ± 0.20	NA^c
8b-7	1.70 ± 0.09	NA^c	42.57 ± 0.16	NA^c
8b-8	0.49 ± 0.22	NA^c	25.04 ± 0.23	NA^c
8b-9	2.73 ± 0.43	NA^c	31.51 ± 0.14	NA^c
8b-10	1.06 ± 0.18	NA^c	42.30 ± 0.64	NA^c
8b-11	0.51 ± 0.09	NA^c	81.22 ± 0.38	289. ± 1.0
8b-12	0.97 ± 0.13	NA^c	27.26 ± 0.27	NA^c
8b-13	6.14 ± 0.12	NA^c	32.03 ± 0.74	NA^c
galantamine	98.52 ± 0.12	12.67 ± 0.07	96.21 ± 0.18	34.05 ± 0.32

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The most potent compound is given in bold.

Inhibition % and IC₅₀ values represent the concentration of inhibitor required to decrease enzyme activity by 50% and are the mean of three independent experiments, each performed in triplicate (SD = standard deviation).

NA = no activity. Compounds defined as “no activity” means that the percent inhibition is less than 50% at a concentration of 10.0 mM in the assay conditions. AChE from electric eel., BuChE from horse serum.

The series of acetoxy analogues 8a with a diverse range of substituents on the triazole ring resulting in different activities were indicated by both the % inhibition of BuChE and IC₅₀ values. Genipin analogue 8a-1 bearing phenyl triazole exhibited moderate inhibitory activity against BuChE, and replacement with 4-OMe and 4-F aryltriazole (8a-2 and 8a-3) resulted in the loss of activity.

Di- and triphenyl, benzyl ether, and benzylamine triazole genipin 8a-4–8a-9 showed no improved activity compared to phenyl triazole genipin 8a-1–8a-3. When triazoles were substituted with an alkyl chain (8a-10–8a-19), they exhibited low to high inhibitory activity. Surprisingly, genipin analogue 8a-10 with a bromoethyltriazole scaffold exhibited the most potent inhibitory activity with an IC₅₀ value of 31.8 μM better than galantamine (IC₅₀ value: 34.1 μM). In contrast, triazolgenipin containing long-chain aliphatic groups showed lower activity than the compound comprising a bromoethyl group (8a-10). Furthermore, the replacement of the long-chain alkyl group with phthalimide scaffolds (8a-21–8a-23) leads to significant improvement in BuChE inhibitory potencies and exhibited IC₅₀ values of 273.9, 203.4, and 418.5 μM, respectively. Hydroxy-cyclic compounds such as 8a-25 and 8a-26 showed no significant change in inhibitory activity.

The series of hemiacetal triazole genipin analogues 8b exhibited promising inhibitory potential against BuChE. The behavior of phenyl substitution in the triazole ring (8b-1–8b-4) showed relatively more than 50% inhibitory potential against BuChE. Among all investigated compounds, the diphenylhydroxy analogue 8b-4 displayed the most potent inhibitory potential against BuChE with an IC₅₀ of 54.3 μM. While alkyl-chain-substituted compounds 8b-5–8b-9 and the hydroxy-cyclic analogues 8b-12 and 8b-13 showed less inhibitory activities. Changing to phthalimide groups at triazoles (8b-10 and 8b-11) increased the inhibitory activity but less than compound 8b-4. Triazole genipin 8a-10 with a bromoethyl group showed the best BuChE inhibitory activity (IC₅₀ = 31.8 μM) and selectivity toward BuChE, surpassing that of the control galantamine (IC₅₀ = 34.1 μM), while 8b-4 with a diphenylhydroxy group showed comparable activity to galantamine.

Compared with the report of neuroprotective activity of piperazine-genipin analogues (Figure 2) by Huang et al.,¹⁹ triazole genipin analogues 8a-11 in this work showed neuroprotective capability (83.5% of cell viability at 0.075 μM) higher than piperazine analogues in the previous report (22.29% at 32 μM). Moreover, triazole genipin analogues showed selective BuChE activity better than galantamine while piperazine analogues exhibited inhibitory potential against anti-AChE.

2.2.3. Kinetic Study for the Inhibition of BuChE

To gain further insights into the inhibitory mechanism of 1,2,3-triazole-genipin analogues, the kinetic behavior of the most active compounds 8a-10 and 8b-4 was investigated using Ellman’s method reference. The inhibition model and inhibition constant K_i were obtained from plots between 1/velocity versus 1/substrate produced with five different concentrations of the substrate butylthiocholine iodide (0.3125, 0.625, 1.25, 2.5, and 5.0 mM). The results showed that the plots of 1/vversus 1/[S] gave straight lines with different slopes but the same x-intercept points. This graphical presentation of Lineweaver–Burk plots indicated that the selected compounds were a noncompetitive enzyme inhibitor and the inhibition constants (KI, KIS) are nearly identical. The inhibition constants (KI, KIS) for compounds 8a-10 and 8b-4 were estimated to be 0.03 and 0.1 mM, respectively (Figure 6).

Lineweaver–Burk plot for the inhibition of BuChE by compounds **8a-10** and **8b-4** at different concentrations of substrate.

2.2.4. Docking Study of BuChE

The molecular docking simulation study of the most potent compounds 8a-10 and 8b-4 was performed to understand the inhibition mechanism within the active site of the target enzymes BuChE (PDB code: 4BDS) using AutoDock 4.2 software.

Analog 8a-10 showed a good fit in the pocket site of the enzyme by interaction with important amino acid residues and exhibited a binding free energy of −9.77 kcal/mol with BuChE (Table 3). Molecular docking of 8a-10 showed three hydrogen bonds of the ester unit at the C4-position of the iridoid moiety with the residues His438 (catalytic subsite) and Ser198 of the CAS along with the interaction of the acetoxy group at the C1-position. The carbonyl group of acetoxy formed three hydrogen bonds with the Trp82 (a key residue in the CAS of BuChE), Trp430, and Tyr440 moieties. Furthermore, the triazole group also formed a hydrogen-bond interaction with the Tyr332 and showed remarkable ionic interaction with Asp70 residue in the PAS region (Figure 7). These interaction behaviors indicated the potential of 8a-10 to inhibit BuChE. The molecular docking studies of 8b-4 also showed preferential interaction with the active site of BuChE with a binding energy of −9.74 kcal/mol (Table 3). The iridoid core of 8b-4 is mostly surrounded by residues of the CAS pocket while diphenyl moiety is oriented toward the PAS pocket. The carbonyl group of the iridoid formed a hydrogen-bond interaction with the Trp82, a key residue in the CAS of BuChE. Meanwhile, the diphenylhydroxy group of 8b-4 showed the same binding orientation within the active site of the target enzyme via two π–π interactions with Tyr332 (a key residue in the PAS of BuChE) (Figure 8). Furthermore, hydrogen bonds and a π–π interaction between the triazole moiety and His438, Ser198, and Phe329 of the CAS were also observed (Figure 8). The modification of introducing a substituted triazole to genipin led to analogues 8a-10 and 8b-4, which increased the potential interaction of the molecule with Trp82 and Tyr332, the important active site of BuChE.

Table 3. Molecular Docking Analysis of BuChE with 1,2,3-Triazole-genipin Analogues 8a-10 and 8b-4^a.

		intermolecular hydrogen bonding
compounds	binding energy (kcal/mol)	amino acid interaction	distance (Å)	intermolecular π–π interaction
8a-10	–9.77	Trp82	2.10	Asp70
		Ser198	1.92
		Ser198	2.01
		Tyr332	2.98
		Trp430	2.22
		His438	2.03
		Tyr440	1.84
8b-4	–9.74	Trp82	2.34	Tyr332, Trp231, Phe329
		Tyr440	2.11
		Trp430	2.25
		Ser198	2.06
		Ser198	2.66

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The binding energies were evaluated using AutoDock 4.2 software.

Proposed binding mode of compound **8a-10** in the active site of BuChE (PDB code: 4BDS).

Proposed binding mode of compound **8b-4** in the active site of BuChE (PDB code: 4BDS). (A) The protein structure is shown as a ribbon, and 1,2,3-triazole-genipin **8b-4** is shown as a stick model. (B) Two-dimensional (2D) interaction molecular docking diagrams. Hydrogen bonds and π–π interactions are shown as green and pink dotted lines, respectively.

3. Conclusions

In summary, a novel series of 1,2,3-triazole-genipin analogues 8 were successfully designed and synthesized as efficient multitarget agents for the treatment of AD. Among the synthesized compounds, analogues 8a-10 and 8b-4 were found as the most active inhibitors with IC₅₀ values of 31.8 and 54.3 μM, respectively. These two analogues also showed inhibitory activity of BuChE selectively over AChE and showed better activity than the standard drug galantamine. Moreover, compounds 8a-10 and 8b-4 were able to rescue the cells from the toxicity induced by H₂O₂. Molecular docking studies of these two compounds confirmed their preferable binding with BuChE and showed interactions with key amino acid residues. Therefore, 1,2,3-triazole-genipin analogues 8a-10 and 8b-4 have the potential for the treatment of neurodegenerative diseases.

4. Experimental Section

All chemicals were purchased from commercial sources and used without further purification. Proton NMR spectra were recorded using a BRUKER AVANC (400 MHz) spectrometer. All spectra were recorded in CDCl₃ solvent, and chemical shifts are reported as δ values in parts per million (ppm) relative to tetramethylsilane (δ 0.00), CDCl₃ (δ 7.26) as internal standard. Carbon NMR spectra were recorded on a BRUKER AVANC (100 MHz) spectrometer. All spectra were recorded in CDCl₃ solvent, and chemical shifts are reported as δ values in parts per million (ppm) relative to CDCl₃ (δ 77.0) as the internal standard. High-resolution mass spectra (HRMS) were recorded at Naresuan University. Analytical thin-layer chromatography (TLC) was conducted on precoated TLC plates; silica gel 60F-254 [E. Merck, Darmstadt, Germany]. Silica gel columns for open-column chromatography utilized silica gel 60 PF254 [E. Merck, Darmstadt, Germany]. Melting points were measured using a melting point apparatus (Griffin) and are uncorrected. Genipin as a starting material (CAS No. 6902-77-8) was purchased from commercial sources and used without further purification.

4.1. Synthesis of Compound 2

To a rapidly stirring solution of genipin 1 (2.00 g, 8.850 mmol) in pyridine (10.0 mL) was added tert-butyldimethylsilyl chloride (2.00 g, 13.275 mmol) at room temperature. The reaction mixture was stirred at room temperature for 10 min. After TLC showed that the reaction was complete, the mixture was diluted with EtOAc (30 mL), quenched with saturated NH₄Cl solution, and then extracted with EtOAc. The mixture was quenched with CuSO₄·5H₂O to remove the pyridine and extracted with EtOAc and washed with brine, the combined organic layers were dried over anhydrous Na₂SO₄, and the solvent was removed by rotary evaporation to obtain the crude product of compound 2.

4.2. Synthesis of Compound 3

To a solution of crude product compound 2 (8.85 mmol) in DCM (20 mL), imidazole (1.8 g, 26.55 mmol) was added and stirred for 10 min, then acetic anhydride (2.5 mL, 26.55 mmol) or tert-butyldiphenylsilyl chloride (6.9 mL, 26.55 mmol) was added to the mixture, and stirred at room temperature for further 1 h. After TLC indicated that the reaction was complete, the reaction mixture was diluted with DCM (10 mL) and quenched with cold-saturated NaHCO₃, extracted with DCM and washed with brine, then dried over with Na₂SO₄ anhydrous, and concentrated in vacuo to obtain crude product 3a and 3b.

4.3. Synthesis of Compound 4

To a stirred solution of compound 3a or 3b (8.85 mmol) in THF (20 mL) was added HCOOH/H₂O (9:1) (40 mL) dropwise at 0 °C and stirred for 6 h. After TLC showed that the reaction was complete, the reaction mixture was diluted with EtOAc (30 mL) and quenched with cold-saturated NaHCO₃ and the mixture was extracted with EtOAc. The combined organic extracts were washed with brine solution, dried (Na₂SO₄), filtered, and concentrated to obtain a crude product of compound 4a or 4b.

4.4. Synthesis of Compounds 5 and 6

To a solution of crude products 4a and 4b (8.85 mmol) in DCM (50 mL), Et₃N (1.8 mL, 13.28 mmol) was added and stirred for 30 min. Then, methanesulfonyl chloride (1.0 mL, 13.28 mmol) was added to the reaction mixture at 0°C and stirred at room temperature for 24 h. After TLC showed that the reaction was complete, the reaction mixture was diluted with DCM (30 mL) and cold-saturated NaHCO₃. The reaction mixture was extracted with DCM, washed with water, then dried over anhydrous Na₂SO₄, filtered, and evaporated in vacuo to obtain the mesylate crude product (5a, 5b). The mesylate of crude product (5a, 5b) was dissolved in DMF (30 mL), and NaN₃ (0.863 g, 13.28 mmol) was added at 0 °C. The reaction was stirred at room temperature, and stirring was continued for 30 min. After TLC showed that the reaction was complete, the reaction mixture was diluted with EtOAc (30 mL) and quenched with cooled water. The reaction mixture was extracted with EtOAc, washed with brine, then dried over anhydrous Na₂SO₄, filtered, and evaporated in vacuo to obtain the crude product of 6a and 6b. The crude product 6a was purified by column chromatography (10% EtOAc/n-hexane) to afford 6a in 72% in five steps.

4.5. Synthesis of Compound 7b

To a stirred solution of compound 6b (8.85 mmol) in DCM (30 mL), TBAF (2.5 g, 9.735 mmol) was added at 0 °C and stirred for 30 min. After TLC showed that the reaction was complete, the reaction mixture was diluted with DCM (30 mL) and quenched with cold-saturated NH₄Cl. The reaction mixture was extracted with DCM, washed with H₂O and brine, followed by drying over with Na₂SO₄ anhydrous, and concentrated in vacuo to obtain crude product and purified by column chromatography (10% EtOAc/n-hexane) to afford compound 7b in 43% in six steps.

4.6. General Procedure for the Preparation of 1,2,3-Triazole-genipin Analogues (8a), (8b)

To the solution of compound 6a (100 mg, 0.3413 mmol) or compound 7b (100 mg, 0.3980 mmol) in CH₃CN (1.0 mL) were added CuI (20 mol %), Et₃N (0.5 equiv), and alkyne (1.5 equiv). After TLC indicated that the reaction was complete, the reaction mixture was diluted with EtOAc (2 mL), quenched with cooled water, and extracted with EtOAc (3 × 30 mL). The reaction mixture was diluted with water (15 mL) and extracted with EtOAc (3 × 15 mL). The combined organic extracts were washed with brine solution, dried (Na₂SO₄), filtered, and concentrated. The resulting crude product was purified by column chromatography to obtain 1,2,3-triazole-genipin analogues 8a and 8b.

4.6.1. 10-[4′-Phenyl-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-1

52% yield as a yellow oil; IR (film) 2950, 1760, 1705, 1634, 1436, 1179, 764 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.81 (2H, d, J = 7.2 Hz, H-Ar), 7.76 (1H, s, H-5′), 7.50–7.29 (4H, m, H-3, H-Ar), 5.92 (1H, brs, H-7), 5.88 (1H, d, J = 7.6 Hz, H-1), 5.09 (2H, brs, H-10), 3.72 (3H, s, OCH₃), 3.27 (1H, q, J = 7.6 Hz, H-5), 2.94 (1H, dd, J = 16.4, 8.4 Hz, H-6a), 2.72 (1H, t, J = 7.2 Hz, H-9), 2.29–2.14 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.10, 166.91, 151.54, 148.06, 135.86, 134.55, 130.29, 128.75 (2C), 128.16, 125.61 (2C), 119.21, 110.97, 91.59, 51.29, 49.59, 44.90, 38.55, 35.05, 20.90; HRMS (m/z): calcd for C₂₁H₂₁N₃O₅ [M + Na]⁺ 418.1379, found 418.1373.

4.6.2. 10-[4′-(4-Methoxypheny)l-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-2

75% yield as a yellow solid, mp: 110–112 °C; IR (film) 2970, 1739, 1712, 1626, 1499, 1216, 764 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.75 (2H, d, J = 8.8 Hz, H-Ar), 7.66 (1H, s, H-5′), 7.45 (1H, brs, H-3), 6.95 (2H, d, J = 8.8 Hz, H-Ar), 5.93 (1H, brs, H-7), 5.89 (1H, d, J = 7.6, Hz, H-1), 5.08 (2H, brs, H-10), 3.84 (3H, s, OCH₃), 3.73 (3H, s, OCH₃), 3.28 (1H, q, J = 8.0 Hz, H-5), 2.95 (1H, dd, J = 16.4, 7.6 Hz, H-6a), 2.73 (1H, t, J = 7.6 Hz, H-9), 2.29–2.17 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 168.95, 166.77, 159.42, 151.37, 147.68, 135.80, 134.25, 126.75(2C), 122.90, 118.44, 114.01(2C), 110.86, 91.43, 55.04, 51.13, 49.36, 44.77, 38.39, 34.85, 20.74; HRMS (m/z): calcd for C₂₂H₂₃N₃O₆ [M + Na]⁺ 448.1485, found 448.1486.

4.6.3. 10-[4′-(4-Fluorophenyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-3

78% yield as a yellow solid, mp: 110–113 °C; IR (film) 2970, 1738, 1700, 1633, 1499, 1229, 1155, 1047, 823 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.83–7.76 (2H, m, H-Ar), 7.71 (1H, s, H-5′), 7.44 (1H, s, H-3), 7.11 (2H, t, J = 8.8 Hz, H-Ar), 5.94 (1H, brs, H-7), 5.89 (1H, d, J = 7.6, H-1), 5.09 (2H, brs, H-10), 3.73 (3H, s, OCH₃), 3.28 (1H, q, J = 8.0 Hz, H-5), 2.95 (1H, dd, J = 17.2, 8.8 Hz, H-6a), 2.72 (1H, t, J = 7.6 Hz, H-9), 2.29–2.17 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.01, 166.81, 162.68 (d, J_C–F = 246 Hz, C–F), 151.42, 147.04, 135.72, 134.53, 127.30 (d, J_C–F = 8.0 Hz, C–F), 127.22 (d, J_C–F = 3.0 Hz, C–F), 126.50, 119.06, 115.73, 115.52, 110.91, 91.45, 51.21, 49.50 44.85, 38.45, 34.90, 20.80; HRMS (m/z): calcd for C₂₁H₂₀FN₃O₅ [M + Na]⁺ 436.1285, found 436.1284.

4.6.4. 10-[4′-(6′,6′-Diphenyl-6′-hydroxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-4

99% yield as a yellow oil; IR (film) 3300, 2949, 1759, 1704, 1634, 1447, 1180, 1083, 759, 699 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.43 (1H, brs, H-3), 7.38–7.27 (10H, m, H-Ar), 7.12 (1H, s, H-5′), 5.85 (1H, d, J = 7.2 Hz, H-1), 5.82 (1H, s, H-7), 5.01 (2H, brs, H-10), 3.73 (3H, s, OCH₃), 3.71 (1H, s, OH), 3.25 (1H, q, J = 8.0 Hz, H-5), 2.92 (1H, dd, J = 18.2, 8.0 Hz, H-6a), 2.71 (1H, t, J = 7.6 Hz, H-9), 2.27–2.12 (4H, m, H-6b, CH₃–OAc); ¹³C NMR (100 MHz, CDCl₃): δ 168.95, 166.84, 154.23, 151.40, 145.58, 145.53, 135.53, 134.15, 127.82 (4C), 127.28 (2C), 127.02 (3C), 126.99, 122.39, 110.94, 91.35, 76.49, 51.21, 49.35, 45.06, 38.38, 34.65, 20.76; HRMS (m/z): calcd for C₂₈H₂₇N₃O₆ [M + H]⁺ 474.2030, found 474.2036. [M + Na]⁺ 496.2788, found 496.2786.

4.6.5. 10-[4′-(Benzyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-5

86% yield as a yellow oil; IR (film) 2927, 1754, 1705, 1634, 1436, 1179, 1080, 767 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.53 (1H, s, H-5′), 7.43 (1H, brs, H-3), 7.35–7.27 (5H, m, H-Ar) 5.88–5.83 (2H, s, H-7, H-1), 5.02 (2H, brs, H-10), 4.67 (2H, s, CH₂), 4.59 (2H, s, CH₂), 3.71 (3H, s, OCH₃), 3.24 (1H, q, J = 8.0 Hz, H-5), 2.91 (1H, dd, J = 16.0, 8.0 Hz, H-6a), 2.67 (1H, t, J = 7.6 Hz, H-9), 2.26–2.14 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.02, 166.89, 151.50, 145.55, 137.63, 135.71, 134.51, 128.30 (2C), 127.77 (2C), 127.67, 122.17, 110.95, 91.57, 72.49, 63.58, 51.27, 49.45, 44.82, 38.49, 34.98, 20.88; HRMS (m/z): calcd for C₂₃H₂₅N₃O₆ [M + Na]⁺ 462.1641, found 462.1640.

4.6.6. 10-[4′-(4-Methoxybenzyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-6

82% yield as a colorless oil; IR (film) 2970, 1755, 1706, 1612, 1513, 1179, 1080 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.52 (1H, brs, H-5′), 7.44 (1H, s, H-3), 7.27 (2H, d, J = 8.4 Hz, H-Ar), 6.87 (2H, d, J = 8.4 Hz, H-Ar), 5.87 (1H, brs, H-7), 5.84 (1H, d, J = 8.0 Hz, H-1), 5.03 (2H, brs, H-10), 4.64 (2H, s, OCH₂), 4.53 (2H, s, OCH₂), 3.79 (3H, s, OCH₃), 3.72 (3H, s, OCH₃), 3.25 (1H, q, J = 8.0 Hz, H-5), 2.92 (1H, dd, J = 17.2, 8.0 Hz, H-6a), 2.68 (1H, t, J = 7.6 Hz, H-9), 2.28–2.13 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.01, 166.87, 159.19, 151.48, 145.61, 135.72, 134.46, 129.69, 129.43 (2C), 122.15, 113.69 (2C), 110.95, 91.55, 72.12, 63.23, 55.12, 51.25, 49.41, 44.81, 38.48, 34.95, 20.86; HRMS (m/z): calcd for C₂₄H₂₇N₃O₇ [M + Na]⁺ 492.1747, found 492.1745.

4.6.7. 10-[4′-(3,4-Dimethoxybenzyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-7

72% yield as a colorless oil; IR (film) 2948, 1758, 1705, 1634, 1515, 1179, 1080, 766 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.53 (1H, brs, H-5′), 7.43 (1H, s, H-3), 6.93–6.79 (3H, m, H-Ar), 5.90–5.80 (2H, m, H-7, H-1), 5.03 (2H, brs, H-10), 4.64 (2H, brs, CH₂), 4.53 (2H, brs, CH₂), 3.87 (3H, s, OCH₃), 3.86 (3H, s, OCH₃), 3.71 (3H, s, OCH₃), 3.25 (1H, q, J = 7.6 Hz, H-5), 2.91 (1H, dd, J = 17.2, 8.0 Hz, H-6a), 2.68 (1H, t, J = 8.0 Hz, H-9), 2.27–2.14 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.03, 166.89, 151.50, 148.92, 148.64, 145.54, 135.72, 134.56, 130.15, 122.20, 120.51, 111.25, 110.96, 110.84, 91.57, 72.45, 63.25, 55.81, 55.76, 51.30, 49.47, 44.85, 38.51, 35.00, 20.90; HRMS (m/z): calcd for C₂₅H₂₉N₃O₈ [M + Na]⁺ 522.1852, found 522.1851.

4.6.8. 10-[4′-(N-Methyl-N-benzylamine)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-8

99% yield as a yellow oil; IR (film) 2970, 1753, 1708, 1634, 1436, 1282, 1179, 1081, 740 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.49 (1H, brs, H-5′), 7.44 (1H, s, H-3), 7.40–7.33 (4H, m, H-Ar), 7.32–7.20 (1H, m, H-Ar), 5.88–5.83 (2H, m, H-7, H-1), 5.04 (2H, brs, H-10), 3.76–3.68 (5H, m, OCH₃, CH₂), 3.56 (2H, brs, CH₂), 3.26 (1H, q, J = 8.0 Hz, H-5), 2.93 (1H, dd, J = 16.0, 7.2 Hz, H-6a), 2.68 (1H, t, J = 8.0 Hz, H-9), 2.30–2.21 (4H, m, H-6b, CH₃–Ac), 2.19 (3H, s, CH₃); ¹³C NMR (100 MHz, CDCl₃): δ 169.09, 166.96, 151.56, 145.40, 138.01, 135.87, 134.36, 129.07 (2C), 128.25 (2C), 127.17, 122.50, 111.02, 91.60, 61.23, 51.88, 51.34, 49.54, 44.95, 41.95, 38.55, 35.00, 20.96; HRMS (m/z): calcd for C₂₄H₂₈N₄O₅ [M + H]⁺ 453.2138, found 453.2144.

4.6.9. 10-[4′-(7′-Bromoethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-9

75% yield as a yellow oil; IR (film) 2951, 1755, 1705, 1634, 1436, 1180, 1082, 731, 557 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.46 (1H, brs, H-5′), 7.45 (1H, brs, H-3), 5.87 (1H, brs, H-7), 5.85 (1H, d, J = 7.6 Hz, H-1), 5.04 (2H, brs, H-10), 3.73 (3H, s, OCH₃), 3.66 (2H, t, J = 6.8 Hz, CH₂–Br), 3.33–3.22 (3H, m, CH₂, H-5), 2.94 (1H, dd, J = 16.4, 8.0 Hz, H-6a), 2.68 (1H, t, J = 8.0 Hz, H-9), 2.28–2.16 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 168.89, 166.76, 151.35, 144.91, 135.75, 134.10, 121.46, 110.86, 91.41, 51.16, 49.33, 44.78, 38.37, 34.80, 31.37, 29.13, 20.78; HRMS (m/z): calcd for C₁₇H₂₀BrN₃O₅ [M + H]⁺ 448.0484, found 448.0490.

4.6.10. 10-[4′-(7′-Hydroxyethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-10

81% yield as a yellow oil; IR (film) 3383, 2970, 1753, 1705, 1634, 1436, 1365, 1282, 1179, 1081, 751 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.44 (1H, brs, H-5′), 7.39 (1H, s, H-3), 5.92 (1H, brs, H-7), 5.83 (1H, d, J = 7.6 Hz, H-1), 5.03 (2H, brs, H-10), 3.95 (2H, t, J = 5.6 Hz, CH₂), 3.73 (3H, s, OCH₃), 3.27 (1H, q, J = 8.0 Hz, H-5), 2.99–2.87 (3H, m, H-6a, CH₂), 2.72 (1H, t, J = 8.0 Hz, H-9), 2.30–2.14 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.05, 166.81, 151.34, 146.05, 135.54, 134.40, 121.94, 110.86, 91.33, 61.17, 51.16, 49.36, 44.89, 38.33, 34.66, 28.63, 20.74; HRMS (m/z): calcd for C₁₇H₂₁N₃O₆ [M + H]⁺ 386.1328, found 386.1314.

4.6.11. 10-[4′-(7′-Hydroxypropyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-11

72% yield as a yellow oil; IR (film) 3383, 2948, 1755, 1705, 1634, 1436, 1365, 1217, 1179, 1081, 751 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.44 (1H, brs, H-5′), 7.30 (1H, s, H-3), 5.86 (1H, brs, H-7), 5.84 (1H, d, J = 7.6 Hz, H-1), 5.01 (2H, brs, H-10), 3.74–3.69 (5H, m, OCH_3, CH₂), 3.26 (1H, q, J = 8.0 Hz, H-5), 2.92 (1H, dd, J = 17.2, 8.4 Hz, H-6a), 2.83 (2H, t, J = 7.2 Hz, CH₂), 2.68 (1H, t, J = 7.6 Hz, H-9), 2.27–2.16 (4H, m, H-6b, CH₃–Ac), 1.98–1.89 (2H, m, CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 169.02, 166.86, 151.40, 147.74, 135.78, 134.13, 120.74, 110.89, 91.40, 61.21, 51.19, 49.25, 44.86, 38.36, 34.77, 31.78, 21.77, 20.77; HRMS (m/z): calcd for C₁₈H₂₃N₃O₆ [M + Na]⁺ 400.1485, found 400.1498.

4.6.12. 10-[4′-(tert-Butyldiphenylsilyoxylpropyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-12

76% yield as a yellow oil; IR (film) 2932, 1759, 1709, 1634, 1428, 1282, 1180, 1085, 1052, 701, 504 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.71–7.60 (4H, m, H-Ar), 7.45 (1H, s, H-5′), 7.43–7.33 (6H, m, H-3, H-Ar), 7.16 (1H, s, H-Ar), 5.84 (1H, d, J = 7.6 Hz, H-1), 5.81 (1H, s, H-7), 4.97 (2H, brs, H-10), 3.78–3.68 (5H, m, OCH₃, CH₂), 3.24 (1H, q, J = 7.6 Hz, H-5), 2.91 (1H, dd, J = 17.2, 8.0 Hz, H-6a), 2.84 (2H, t, J = 8.0 Hz, CH₂), 2.67 (1H, t, J = 8.0 Hz, H-9), 2.25–2.14 (4H, m, H-6b, CH₃–Ac), 2.00–1.89 (2H, m, CH₂), 1.02 (9H, s, CH₃); ¹³C NMR (100 MHz, CDCl₃): δ ¹³C NMR (100 MHz, CDCl₃): δ 169.10, 166.99, 151.58, 148.18, 136.11, 135.49 (4C), 134.11 (2C), 133.83, 129.52 (2C), 127.57 (4C), 120.46, 111.04, 91.66, 62.93, 51.33, 49.38, 44.95, 38.56, 35.08, 31.95, 26.81 (3C), 22.04, 20.94, 19.17; HRMS (m/z): calcd for C₃₄H₄₁N₃O₆Si [M + H]⁺ 616.2843, found 616.2853.

4.6.13. 10-[4′-(Triisopropysilyoxylpropyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-13

92% yield as a yellow oil; IR (film) 2943, 2865, 1763, 1709, 1634, 1436, 1282, 1180, 1084, 1052, 767 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.45 (1H, s, H-5′), 7.28 (1H, s, H-3), 5.88–5.82 (2H, m, H-7, H-1), 5.00 (2H, brs, H-10), 3.77–3.70 (5H, m, OCH₃, CH₂), 3.26 (1H, q, J = 8.0 Hz, H-5), 2.92 (1H, dd, J = 16.4, 7.2 Hz, H-6a), 2.82 (2H, t, J = 7.2 Hz, CH₂), 2.67 (1H, t, J = 7.6 Hz, H-9), 2.25–2.16 (4H, m, H-6b, CH₃–Ac), 1.98–1.87 (2H, m, CH₂), 1.08–1.01 (21H, m, CH₃, Si-CH); ¹³C NMR (100 MHz, CDCl₃): δ 168.92, 166.82, 151.43, 148.14, 136.07, 133.97, 120.38, 110.90, 91.55, 62.21, 51.16, 49.24, 44.80, 38.43, 34.97, 32.20, 21.85, 20.78, 17.81 (6C), 11.77 (3C); HRMS (m/z): calcd for C₂₇H₄₃N₃O₆Si [M + H]⁺ 534.2999, found 534.3010.

4.6.14. 10-[4′-(tert-Butyldiphenylsilyoxylethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-14

80% yield as a yellow oil; IR (film) 2931, 1760, 1709, 1634, 1428, 1180, 1082, 701, 502 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.63–7.55 (4H, m, H-Ar), 7.46–7.32 (8H, m, H-5′, H-3, H-Ar), 5.85–5.81 (2H, m, H-1, H-7), 4.99 (2H, brs, H-10), 3.93 (2H, t, J = 6.0 Hz, CH₂), 3.72 (3H, s, OCH₃), 3.19 (1H, q, J =7.6 Hz, H-5), 2.99 (2H, t, J = 6.0 Hz, CH₂), 2.87 (1H, dd, J = 16.8, 8.0 Hz, H-6a), 2.65 (1H, t, J = 7.6 Hz, H-9), 2.23–2.11 (4H, m, H-6b, CH₃–Ac), 1.02 (9H, s, CH₃); ¹³C NMR (100 MHz, CDCl₃): δ 168.93, 166.79, 151.43, 145.53, 135.96 (4C), 135.25, 134.15, 133.32, 129.51, 127.51 (4C), 121.51, 110.88, 91.58, 62.79, 60.15, 51.16, 49.24, 44.66, 38.40, 34.96, 29.10, 26.62 (3C), 20.79, 18.99, 13.99; HRMS (m/z): calcd for C₃₃H₃₉N₃O₆Si [M + H]⁺ 602.2686, found 602.2690.

4.6.15. 10-[4′-(tert-Butylsilyoxylethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-15

80% yield as a yellow oil; IR (film) 2952, 1737, 1709, 1634, 1436, 1180, 1083, 834 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.43 (1H, s, H-5′), 7.36 (1H, s, H-3), 5.87–5.80 (2H, m, H-7, H-1), 4.99 (2H, brs, H-10), 3.85 (2H, t, J = 6.4 Hz, CH₂), 3.71 (3H, s, OCH₃), 3.24 (1H, q, J = 8.4 Hz, H-5), 2.97–2.85 (3H, m, H-6a, CH₂), 2.66 (1H, t, J = 7.6 Hz, H-9), 2.25–2.12 (4H, m, H-6b, CH₃–Ac), 0.84 (9H, s, 3× CH₃) 0.01 (6H, s, 2× CH₃); ¹³C NMR (100 MHz, CDCl₃): δ 168.90, 166.80, 151.42, 145.57, 135.98, 134.06, 122.47, 110.86, 91.53, 61.96, 51.16, 49.21, 44.70, 38.39, 34.93, 29.25 (2C), 25.63 (3C), 20.77, −5.61 (2C); HRMS (m/z): calcd for C₂₃H₃₅N₃O₆Si [M + H]⁺ 478.2373, found 478.2380.

4.6.16. 10-[4′-(Triphenyloxylmethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-16

84% yield as a colorless oil; IR (film) 2950, 1763, 1706, 1634, 1448, 1436, 1284, 1220, 1182, 1087, 704 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.46–7.34 (8H, m, H-5′, H-3, H-Ar), 7.30–7.13 (9H, m, H-Ar), 5.85–5.74 (2H, m, H-7, H-1), 4.97 (2H, brs, H-10), 4.26 (2H, brs, CH₂), 3.66 (3H, s, OCH₃), 3.20 (1H, q, J = 8.0 Hz, H-5), 2.87 (1H, dd, J = 16.8 Hz, 7.6 Hz, H-6a), 2.63 (1H, t, J = 7.2 Hz, H-9), 2.25–2.08 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.13, 167.03, 151.64, 146.49, 143.70 (2C), 135.94, 134.43, 128.64 (6C), 127.91 (6C), 127.14 (4C), 121.65, 111.10, 91.71, 87.37, 58.74, 51.38, 49.56, 45.01, 38.63, 35.11, 20.99; HRMS (m/z): calcd for C₃₅H₃₃N₃O₆ [M + Na]⁺ 614.2267, found 614.2276.

4.6.17. 10-[4′-(Octyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-17

90% yield as a yellow oil; IR (film) 2927, 2856, 1738, 1711, 1634, 1436, 1282, 1217, 1180, 1083 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.52 (1H, s, H-5′), 7.45 (1H, s, H-3), 5.88 (1H, brs, H-7), 5.85 (1H, d, J = 7.6 Hz, H-1), 5.04 (2H, brs, H-10), 4.62 (2H, s, CH₂), 3.73 (3H, s, OCH₃), 3.52 (2H, t, J = 6.4 Hz, CH₂), 3.26 (1H, q, J = 8.0 Hz, H-5), 2.93 (1H, dd, J = 16.8, 8.0 Hz, H-6a), 2.69 (1H, t, J = 7.6 Hz, H-9), 2.28–2.10 (4H, m, H-6b, CH₃–Ac), 1.57–1.54 (2H, m, CH₂), 1.36–1.20 (10H, m, 5× CH₂), 0.87 (3H, t, J = 8.0 Hz, CH₃); ¹³C NMR (100 MHz, CDCl₃): δ 169.02, 166.89, 151.51, 145.88, 135.76, 134.49, 122.03, 110.95, 91.60, 70.89, 64.24, 51.28, 49.54, 44.84, 38.51, 35.01, 31.66, 29.49, 29.27, 29.08, 25.97, 22.49, 20.91, 13.94; HRMS (m/z): C₂₄H₃₅N₃O₆ [M + H]⁺ 434.2666, found 434.2660.

4.6.18. 10-[4′-(Dodecyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-18

89% yield as a yellow oil; IR (film) 2914, 2850, 1742, 1698, 1647, 1446, 1380, 1235, 1081 cm^–1; NMR (400 MHz, CDCl₃): δ 7.52 (1H, s, H-5′), 7.44 (1H, s, H-3), 5.87 (1H, brs, H-7), 5.85 (1H, d, J = 7.6 Hz, H-1), 5.03 (2H, brs, H-10), 4.62 (2H, s, CH₂), 3.73 (3H, s, OCH₃), 3.51 (2H, t, J = 6.4 Hz, CH₂), 3.26 (1H, q, J = 8.0 Hz, H-5), 2.93 (1H, dd, J = 16.8, 8.0 Hz, H-6a), 2.69 (1H, t, J = 7.6 Hz, H-9), 2.27–2.15 (4H, m, H-6b, CH₃–Ac), 1.62–1.54 (2H, m, CH₂), 1.36–1.20 (18H, s, 9× CH₂), 0.87 (3H, t, J = 6.4 Hz, CH₃); ¹³C NMR (100 MHz, CDCl₃): δ 168.97, 166.85, 151.47, 145.87, 135.77, 134.40, 121.99, 110.93, 91.57, 76.98, 70.85, 64.18, 51.23, 49.44, 44.81, 38.48, 34.98, 31.74, 29.48, 29.45 (2C), 29.42, 29.31, 29.17, 25.95, 22.51, 20.85, 13.94 HRMS (m/z): C₂₈H₄₃N₃O₆ [M + H]⁺ 518.3230, found 518.3238.

4.6.19. 10-[4′-((Undec-10-enyloxy)methy)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-19

66% yield as a white solid, mp: 52–56 °C; IR (film) 2923, 2849, 1779, 1698, 1633, 1436, 1180, 1086, 1050 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.52 (1H, s, H-5′), 7.45 (1H, brs, H-3), 5.88 (1H, s, H-7), 5.85 (1H, d, J = 7.6 Hz, H-1) 5.83–5.74 (1H, m, CH-alkene), 5.04 (2H, brs, H-10), 5.02–4.89 (2H, m, CH-alkene), 4.62 (2H, s, CH₂), 3.73 (3H, s, OCH₃), 3.51 (2H, t, J = 6.8 Hz, CH₂), 3.26 (1H, q, J = 7.6 Hz, H-5), 2.93 (1H, dd, J = 16.8, 8.4 Hz, H-6a), 2.69 (1H, t, J = 7.2 Hz, H-9), 2.27–2.17 (4H, m, H-6b, CH₃–Ac), 2.08–1.99 (2H, m, CH₂), 1.66–1.54 (2H, m, CH₂), 1.41–1.23 (12H, m, 6× CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 168.88, 166.77, 151.40, 145.80, 138.92, 135.75, 134.30, 121.96, 113.90, 110.89, 91.51, 70.75, 64.13, 51.16, 49.36, 44.78, 38.43, 34.91, 33.55, 29.41, 29.27, 29.19 (2C), 28.87, 28.68, 25.88, 20.78; HRMS (m/z): calcd for C₂₇H₃₉N₃O₆ [M + Na]⁺ 524.2737, found 524.2740.

4.6.20. 10-[4′-(((Dioxoisoindolin-2-yl)oxy)methyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-20

66% yield as a white solid, mp: 76.6–78.6 °C; IR (film) 2970, 1728, 1633, 1436, 1365, 1217, 1083, 701 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.86 (1H, s, H-5′), 7.80–7.68 (4H, m, H-Ar), 7.46 (1H, brs, H-3), 5.92 (1H, s, H-7), 5.84 (1H, J = 7.6 Hz, H-1), 5.40–5.32 (2H, m, CH₂), 5.04 (2H, brs, H-10), 3.74 (3H, s, OCH₃), 3.30 (1H, q, J = 8.0 Hz, H-5), 2.96 (1H, dd, J = 16.4, 8.4 Hz, H-6a), 2.68 (1H, t, J = 7.6 Hz, H-9), 2.30–2.14 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.09, 166.95, 163.31 (2C), 151.53, 141.86, 135.61, 134.58 (2C), 134.40 (2C), 128.63, 124.48, 123.42 (2C), 111.04, 91.65, 70.09, 51.31, 49.70, 44.60, 38.57, 35.00, 20.91; HRMS (m/z): calcd for C₂₄H₂₂N₄O₈ [M + Na]⁺ 517.1335, found 517.1331.

4.6.21. 10-[4′-((1,3-Dioxoisoindolin-2-yl)methyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-21

99% yield as a white solid, mp: 68.0–72.0 °C; IR (film) 2927, 1738, 1709, 1634, 1428, 1366, 1179, 1082, 713 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.87–7.81 (2H, m, H-Ar), 7.74–7.69 (2H, m, H-Ar), 7.59 (1H, s, H-5′), 7.41 (1H, brs, H-3), 5.86 (1H, brs, H-7), 5.80 (1H, d, J = 7.6 Hz, H-1), 5.03–4.95 (4H, m, H-10, CH₂), 3.71 (3H, s, OCH₃), 3.24 (1H, q, J = 8.0 Hz, H-5), 2.91 (1H, dd, J = 16.8, 8.4 Hz, H-6a), 2.66 (1H, t, J = 7.6 Hz, H-9), 2.25–2.11 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 168.99, 167.50 (2C), 166.86, 151.45, 142.91, 135.55, 134.61 (2C), 133.97 (2C), 131.86, 123.28 (2C), 122.60, 110.90, 91.52, 51.24, 49.46, 44.83, 38.47, 34.89, 32.88, 20.81; HRMS (m/z): calcd for C₂₄H₂₂N₄O₇ [M + Na]⁺ 501.1386, found 501.1385.

4.6.22. 10-[4′-((1,3-Dioxoisoindolin-2-yl)ethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-22

99% yield as a yellow solid, mp: 61.6–64.6 °C; IR (film) 2970, 1738, 1634, 1366, 1217, 1084, 718 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.83–7.77 (2H, m, H-Ar), 7.74–7.66 (2H, m, H-Ar), 7.45 (1H, s, H-5′), 7.40 (1H, brs, H-3), 5.84 (1H, brs, H-7), 5.80 (1H, d, J = 8.0 Hz, H-1), 4.99 (2H, brs, H-10), 4.01 (2H, t, J = 7.2 Hz, CH₂), 3.74 (3H, s, OCH₃), 3.24 (1H, q, J = 8.4 Hz, H-5), 3.16 (2H, t, J = 6.8 Hz, CH₂), 2.91 (1H, dd, J = 16.8, 8.4 Hz, H-6a), 2.60 (1H, t, J = 8.0 Hz, H-9), 2.26–2.14 (4H, m, H-6b, CH₃–Ac); ¹³C NMR (100 MHz, CDCl₃): δ 169.08, 168.01 (2C), 166.95, 151.52, 144.56, 135.90, 134.22 (2C), 133.86 (2C), 131.83, 123.12 (2C), 121.15, 110.97, 91.66, 51.29, 49.46, 44.59, 38.52, 37.30, 35.01, 24.73, 20.89; HRMS (m/z): calcd for C₂₅H₂₄N₄O₇ [M + Na]⁺ 515.1543, found 515.1541.

4.6.23. 10-[4′-((1,3-Dioxoisoindolin-2-yl)propyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-23

77% yield as a brown solid, mp: 130–135 °C; IR (film) 2925, 1738, 1707, 1628, 1432, 1364, 1176, 1079, 723 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.85–7.79 (2H, m, H-Ar), 7.74–7.67 (2H, m, H-Ar), 7.43 (2H, s, H-5′, H-3), 5.86 (1H, brs, H-7), 5.82 (1H, d, J = 7.6 Hz, H-1), 5.00 (2H, brs, H-10), 3.75–3.68 (5H, m, OCH₃, CH₂), 3.26 (1H, q, J = 7.6 Hz, H-5), 2.92 (1H, dd, J = 16.8, 8.4 Hz, H-6a), 2.76 (2H, t, J = 7.6 Hz, CH₂), 2.67 (1H, t, J = 7.6 Hz, H-9), 2.26–2.14 (4H, m, H-6b, CH₃–Ac), 2.11–2.028 (2H, m, CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 169.02, 168.22 (2C), 166.89, 151.46, 146.98, 135.92, 134.22 (2C), 133.82 (2C), 131.88, 123.02 (2C), 120.87, 110.93, 91.61, 51.21, 49.34, 44.78, 38.47, 36.97, 34.97, 27.89, 22.76, 20.85; HRMS (m/z): calcd for C₂₆H₂₆N₄O₇ [M + Na]⁺ 529.1699, found 529.1699.

4.6.24. 10-[4′-((1,3-Dioxoisoindolin-2-yl)butyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-24

60% yield as a brown oil; IR (film) 2943, 1761, 1703, 1634, 1365, 1179, 1081, 719 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.85–7.79 (2H, m, H-Ar), 7.74–7.67 (2H, m, H-Ar), 7.44 (1H, s, H-5′), 7.30 (1H, s, H-3), 5.85 (1H, brs, H-7), 5.83 (1H, d, J = 7.6 Hz, H-1), 5.00 (2H, brs, H-10), 3.75–3.68 (5H, m, OCH₃, CH₂), 3.27 (1H, q, J = 7.6 Hz, H-5), 2.92 (1H, dd, J = 17.2, 8.8 Hz, H-6a), 2.76 (2H, t, J = 6.4 Hz, CH₂), 2.67 (1H, t, J = 7.6 Hz, H-9), 2.26–2.14 (4H, m, H-6b, CH₃–Ac), 1.60–1.80 (4H, m, CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 169.12, 168.32 (2C), 166.99, 151.56, 147.82, 136.00, 134.30 (2C), 133.84 (2C), 132.07, 123.09 (2C), 120.56, 111.01, 91.69, 51.32, 49.40, 44.88, 38.54, 37.47, 35.06, 27.88, 26.46, 24.97, 20.94; HRMS (m/z): calcd for C₂₇H₂₈N₄O₇ [M + Na]⁺ 521.2036, found 521.2034.

4.6.25. 10-[4′-(1-Hydroxycyclohexyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-25

99% yield; IR (film) 2937, 1759, 1706, 1635, 1265, 1181, 1086, 731 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.44 (1H, s, H-5′), 7.43 (1H, s, H-3), 5.89 (1H, brs, H-7), 5.84 (1H, d, J = 7.6 Hz, H-1), 5.03 (2H, brs, H-10), 3.73 (3H, s, OCH₃), 3.27 (1H, q, J = 8.0 Hz, H-5), 2.94 (1H, dd, J = 16.8, 8.4 Hz, H-6a), 2.70 (1H, t, J = 7.6 Hz, H-9), 2.27–2.16 (4H, m, H-6b), 2.03–1.50 (10H, m, 5× CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 169.10, 166.93, 155.93, 151.51, 135.78, 134.67, 119.27, 110.96, 91.56, 69.44, 51.29, 49.44, 45.03, 38.53, 37.94 (2C), 34.96, 25.22, 21.84 (2C), 20.89; HRMS (m/z): calcd for C₂₁H₂₇N₃O₆ [M + H]⁺ 418.1978, found 418.1970.

4.6.26. 10-[4′-(1-Hydroxycyclopentyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-26

99% yield as a white oil; IR (film) 3418, 2951, 1737, 1706, 1634, 1436, 1217, 1179, 1081 cm^–1; ¹H NMR (400 MHz, CDCl₃): 7.45 (1H, s, H-5′), 7.42 (1H, s, H-3), 5.89 (1H, brs, H-7), 5.82 (1H, d, J = 7.6 Hz, H-1), 5.01 (2H, brs, H-10), 3.71 (3H, s, OCH₃), 3.25 (1H, q, J = 7.6 Hz, H-5), 2.91 (1H, dd, J = 16.4, 8.0 Hz, H-6a), 2.69 (1H, t, J = 6.8 Hz, H-9), 2.26–2.13 (4H, m, H-6b, CH₃–Ac), 2.11–1.88 (8H, m, 4× CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 169.15, 166.95, 151.51, 134.78, 134.33, 127.74, 119.19, 110.94, 91.57, 78.94, 51.31, 49.43, 44.82, 41.10, 38.51, 34.96, 33.02, 23.47, 22.96, 20.89; HRMS (m/z): calcd for C₂₀H₂₅N₃O₆ [M + Na]⁺ 426.1641, found 426.1644.

4.6.27. 10-[4′-Phenyl-1H-1,2,3-triazole-1-yl]genipin 8b-1

67% yield as a yellow oil; IR (film) 2921, 1697, 1637, 1437, 1179, 1079, 766 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.82 (1H, s, H-Ar), 7.80 (2H, d, J = 7.2 Hz, H-Ar), 7.50 (1H, s, H-3), 7.46–7.31 (3H, m, H-Ar, H-5′), 5.86 (1H, brs, H-7), 5.32 (1H, d, J = 15.2 Hz H-10a), 5.24 (1H, d, J = 15.6 Hz H-10b), 5.15 (1H, d, J = 8.0 Hz, H-1), 4.88 (1H, t, J = 8.0 Hz, OH), 3.71 (3H, s, OCH₃), 3.15 (1H, q, J = 8.4 Hz, H-5), 2.92 (1H, dd, J = 16.8, 7.6 Hz, H-6a), 2.43 (1H, t, J = 8.0 Hz, H-9), 2.15–2.05 (1H, m, H-6b); ¹³C NMR (100 MHz, CDCl₃): δ 167.75, 152.74, 147.76, 137.82, 132.35, 130.07, 128.84 (2C), 128.33, 125.71 (2C), 120.41, 110.31, 96.37, 51.24, 50.51, 47.22, 39.07, 36.11; HRMS (m/z): calcd for C₁₉H₁₉N₃O₄ [M + Na]⁺ 376.1273, found 376.1276.

4.6.28. 10-[4′-(4-Methoxypheny)l-1H-1,2,3-triazole-1-yl]genipin 8b-2

45% yield as a yellow solid, mp: 148.6–150.6 °C; IR (film) 2923, 1699, 1629, 1499, 1106, 733 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.77–7.70 (3H, m, H-Ar, H- H-5′), 7.51 (1H, brs, H-3), 6.95 (2H, d, J = 8.8 Hz, H-Ar), 5.87 (1H, brs, H-7), 5.32 (1H, d, J = 15.6, Hz, H-10a), 5.21 (1H, d, J = 15.6 Hz, H-10b), 4.98 (1H, d, J = 6.8 Hz, H-1), 4.87 (1H, t, J = 8.0 Hz, OH), 3.84 (3H, s, OCH₃), 3.71 (3H, s, OCH₃), 3.15 (1H, q, J = 8.8 Hz, H-5), 2.92 (1H, dd, J = 16.8, 8.8 Hz, H-6a), 2.42 (1H, t, J = 8.0 Hz, H-9), 2.15–2.06 (1H, m, H-6b); ¹³C NMR (100 MHz, CDCl₃): δ 167.78, 159.69, 152.79, 147.59, 137.93, 132.23, 127.04 (2C), 122.74, 119.66, 114.24 (2C), 110.26, 96.39, 55.27, 51.23, 50.47, 47.21, 39.06, 36.12; HRMS (m/z): calcd for C₂₀H₂₁N₃O₅ [M + H]⁺ 384.1559, found 384.1568.

4.6.29. 10-[4′-(4-Fluorophenyl)-1H-1,2,3-triazole-1-yl]genipin 8b-3

78% yield as a yellow solid, mp: 156.6–159.6 °C; IR (film) 2923, 1705, 1628, 1497, 1226, 1105, 768 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.81–7.74 (3H, s, H-Ar), 7.50 (1H, s, H-3), 7.11 (2H, t, J = 8.8 Hz, H-Ar, H-5′), 5.88 (1H, brs, H-7), 5.33 (1H, d, J = 15.6 Hz, H-10a), 5.23 (1H, d, J = 16.0 Hz, H-10b), 4.88 (1H, d, J = 6.4 Hz, H-1), 4.80 (1H, brs, OH), 3.71 (3H, s, OCH₃), 3.16 (1H, q, J = 8.4 Hz, H-5), 2.94 (1H, dd, J = 16.8, 8.0 Hz, H-6a), 2.42 (1H, t, J = 8.4 Hz, H-9), 2.16–2.05 (1H, m, H-6b); ¹³C NMR (100 MHz, CDCl₃): δ 167.69, 162.72 (d, J_C–F = 247 Hz, C–F), 152.64, 146.97, 137.71, 132.59, 127.47 (d, J_C–F = 8.0 Hz, 2C–F), 126.32 120.09, 115.96, 115.74, 110.38, 96.35, 51.28, 50.52, 47.17, 39.08, 36.12; HRMS (m/z): calcd for C₁₉H₁₈FN₃O₄; [M + Na]⁺ 394.1179, found 394.1184.

4.6.30. 10-[4′-(6′,6′-Diphenyl-6′-hydroxymethyl)-1H-1,2,3-triazole-1-yl]genipin 8b-4

64% yield as a white solid, mp: 76.6–80.6 °C; IR (film) 3384, 2924, 1700, 1626, 1446, 1103, 697 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.44 (1H, s, H-3), 7.35–7.22 (10H, m, H-Ar), 7.15 (1H, s, H-5′), 5.77 (1H, s, H-7), 5.23 (1H, d, J = 16.0 Hz, H-10a), 5.09 (1H, d, J = 15.6 Hz, H-10b), 4.99 (1H, t, J = 6.4 Hz, OH), 4.81–4.73 (1H, m, H-1), 3.92–3.85 (1H, m, OH), 3.72 (3H, s, OCH₃), 3.10 (1H, q, J = 8.4 Hz, H-5), 2.89 (1H, dd, J = 16.4, 8.0 Hz, H-6a), 2.34 (1H, t, J = 8.4 Hz, H-9), 2.11–1.98 (1H, m, H-6b); ¹³C NMR (100 MHz, CDCl₃): δ 167.71, 153.85, 152.59, 145.47, 145.41, 137.72, 132.05, 127.96 (4C), 127.48, 127.45 (2C), 127.08 (3C) 123.50, 110.14, 96.17, 76.53, 51.19, 50.34, 47.09, 38.84, 35.98; HRMS (m/z): calcd for C₂₆H₂₅N₃O₅ [M + H]⁺ 460.1872, found 460.1871.

4.6.31. 10-[4′-(tert-Butyldiphenylsilyoxylpropyl)-1H-1,2,3-triazole-1-yl]genipin 8b-5

76% yield as a yellow oil; IR (film) 2928, 2854, 1702, 1632, 1440, 1107, 703, 504 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.70–7.65 (4H, m, H-Ar), 7.55 (1H, s, H-3), 7.50- 7.35 (6H, m, H-Ar), 7.31 (1H, s, H-5′), 5.79 (1H, brs, H-7), 5.52 (1H, brs, OH), 5.25 (1H, d, J = 15.6 Hz, H-10a), 5.16 (1H, d, J = 15.6 Hz, H-10b), 4.88 (1H, d, J = 8.8 Hz, H-1), 3.80–3.70 (5H, m, OCH₃, CH₂), 3.17 (1H, q, J = 8.4 Hz, H-5), 2.95 (1H, dd, J = 16.8, 8.8 Hz, H-6a), 2.88 (2H, t, J = 7.6 Hz, CH₂), 2.40 (1H, t, J = 7.2 Hz, H-9), 2.17–2.05 (1H, m, H-6b), 2.05–1.93 (2H, m, CH₂), 1.20–1.00 (9H, m, CH₃ × 3); ¹³C NMR (100 MHz, CDCl₃): δ 167.73, 152.78, 147.85, 138.15, 135.50 (4C), 133.80, 131.69, 129.42 (3C), 127.60 (4C), 121.55, 110.27, 96.31, 62.88, 51.18, 50.21, 47.23, 39.03, 36.10, 31.90, 26.83 (3C), 21.91, 19.18; HRMS (m/z): calcd for C₃₂H₃₉N₃O₅Si [M + Na]⁺ 596.2557, found 596.2554.

4.6.32. 10-[4′-(tert-Butyldiphenylsilyoxylpropyl)-1H-1,2,3-triazole-1-yl]genipin 8b-6

78% yield as a colorless oil; IR (film) 2931, 1698, 1628, 1428, 1103, 701, 503 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.66 (4H, d, J = 6.8 Hz, H-Ar), 7.49 (1H, s, H-5′), 7.45–7.31 (7H, m, H-Ar, H-3), 5.74 (1H, brs, H-7), 5.32–5.08 (3H, m, H-10, OH), 4.88 (2H, s, CH₂), 4.85–4.78 (1H, m, H-1), 3.72 (3H, s, OCH₃), 3.11 (1H, q, J = 8.4 Hz, H-5), 2.91 (1H, dd, J = 16.0, 8.0 Hz, H-6a), 2.31 (1H, t, J = 7.6 Hz, H-9), 2.12–2.00 (1H, m, H-6b), 1.20–1.00 (9H, m, CH₃ × 3), ¹³C NMR (100 MHz, CDCl₃): ¹³C NMR (100 MHz, CDCl₃): δ 167.74, 152.76, 148.07, 137.99, 135.48 (4C), 133.05, 131.83, 129.81 (3C), 127.73 (4C), 122.40, 110.24, 96.29, 58.40, 51.19, 50.34, 47.16, 39.03, 36.08, 26.74 (3C), 19.14. HRMS (m/z): calcd for C₃₀H₃₅N₃O₅Si [M + Na]⁺ 568.2244, found 568.2245.

4.6.33. 10-[4′-(Octyloxymethyl)-1H-1,2,3-triazole-1-yl]genipin 8b-7

55% yield as a yellow oil; IR (film) 2926, 1708, 1628, 1436, 1083, 793 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.62 (1H, s, H-5′), 7.50 (1H, brs, H-3), 5.80 (1H, brs, H-7), 5.27–5.18 (3H, m, H-10, OH), 4.88–4.80 (1H, m, H-1), 4.62 (2H, s, CH₂), 3.71 (3H, s, OCH₃), 3.51 (2H, t, J = 6.8 Hz, CH₂), 3.14 (1H, q, J = 8.8 Hz, H-5), 2.91 (1H, dd, J = 16.8, 8.0 Hz, H-6a), 2.38 (1H, t, J = 7.6 Hz, H-9), 2.13–2.05 (1H, m, H-6b), 1.63–1.54 (2H, m, CH₂), 1.35–1.20 (10H, m, 5× CH₂), 0.87 (3H, t, J = 6.8 Hz, CH₃); ¹³C NMR (100 MHz, CDCl₃): δ 167.85, 152.84, 145.26, 138.08, 132.05, 123.43, 110.24, 96.35, 71.08, 64.02, 51.17, 50.29, 47.13, 39.13, 36.10, 31.76, 29.54, 29.37, 29.18, 26.04, 22.59, 14.04; HRMS (m/z): C₂₂H₃₃N₃O₅ [M + H]⁺ 420.2498, found 420.2502.

4.6.34. 10-[4′-(Dodecyloxymethyl)-1H-1,2,3-triazole-1-yl]genipin 8b-8

53% yield as a brown oil; IR (film) 2922, 2853, 1738, 1712, 1629, 1436, 1102 cm^–1; NMR (400 MHz, CDCl₃): δ 7.61 (1H, s, H-5′), 7.49 (1H, s, H-3), 5.79 (1H, brs, H-7), 5.27 (1H, brs, OH), 5.25 (1H, d, J = 15.6 Hz, H-10a), 5.18 (1H, d, J = 15.6 Hz, H-10b), 4.83 (1H, d, J = 8.4 Hz, H-1), 4.60 (2H, s, CH₂), 3.70 (3H, s, OCH₃), 3.50 (2H, t, J = 6.4 Hz, CH₂), 3.13 (1H, q, J = 8.8 Hz, H-5), 2.90 (1H, dd, J = 16.4, 8.8 Hz, H-6a), 2.39 (1H, t, J = 7.2 Hz, H-9), 2.11–2.04 (1H, m, H-6b), 1.62–1.53 (2H, m, CH₂), 1.37–1.19 (18H, s, 9× CH₂), 0.86 (3H, t, J = 6.4 Hz, CH₃); ¹³C NMR (100 MHz, CDCl₃): δ 167.72, 152.71, 145.30, 137.90, 132.12, 123.23, 110.21, 96.26, 70.99, 64.00, 51.18, 47.07, 38.94, 36.03, 31.80, 29.55, 29.52 (4C), 29.49, 29.38, 29.24, 25.98, 22.57, 14.00; HRMS (m/z): C₂₆H₄₁N₃O₅ [M + H]⁺ 476.3124, found 476.3120.

4.6.35. 10-[4′-((Undec-10-enyloxy)methy)-1H-1,2,3-triazole-1-yl]genipin 8b-9

69% yield as a brown oil; IR (film) 2925, 2854, 1706, 1629, 1437, 1083, 734 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.66 (1H, s, H-5′), 7.48 (1H, brs, H-3), 5.85–5.75 (1H, m, CH-alkene), 5.73 (1H, s, H-7), 5.22–5.14 (2H, m, H-10), 5.01–4.81 (3H, m, H-1, CH × 2), 4.60 (2H, s, CH₂), 3.70 (3H, s, OCH₃), 3.50 (1H, t, J = 8.0 Hz, CH₂), 3.14 (1H, q, J = 8.8 Hz, H-5), 2.88 (1H, dd, J = 16.4 Hz, 8.0 Hz, H-6a), 2.41 (1H, t, J = 8.0 Hz, H-9), 2.10–1.97 (3H, m, CH_2, H-6b), 1.62–1.50 (2H, m, CH₂), 1.40–1.19 (14H, m, 7× CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 167.69, 152.68, 145.17, 139.02, 137.91, 131.92, 123.20, 113.97, 110.13, 96.21, 70.89, 63.92, 51.13, 50.31, 46.98, 38.94, 35.96, 33.63, 29.52, 29.42, 29.35, 29.27, 28.94, 28.74, 25.91; HRMS (m/z): calcd for C₂₅H₃₇N₃O₅ [M + H]⁺ 482.2631, found 482.2630.

4.6.36. 10-[4′-(((Dioxoisoindolin-2-yl)oxy)methyl)-1H-1,2,3-triazole-1-yl] 8b-10

68% yield as a white solid, mp: 57.6–61.6 °C; IR (film) 2923, 2853, 1729, 1627, 1437, 1081, 699 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.92 (1H, s, H-5′), 7.76–7.68 (4H, m, H-Ar), 7.53 (1H, brs, H-3), 5.98 (1H, s, H-7), 5.37 (2H, s, CH₂), 5.30–5.14 (2H, m, H-10), 4.82–4.68 (2H, m, H-1, OH), 3.73 (3H, s, OCH₃), 3.18 (1H, q, J = 8.8 Hz, H-5), 2.96 (1H, dd, J = 15.6, 8.4 Hz, H-6a), 2.28 (1H, t, J = 8.0 Hz, H-9), 2.16–2.06 (1H, m, H-6b); ¹³C NMR (100 MHz, CDCl₃): δ 167.69, 163.47 (2C), 152.59, 141.23, 137.45, 134.47 (2C), 132.82, 128.46, 125.65, 123.44 (2C), 110.18, 96.24, 69.90, 51.16, 50.40, 47.08, 39.01, 35.93, 29.52; HRMS (m/z): calcd for C₂₂H₂₀N₄O₇ [M + H]⁺ 453.1410, found 453.141

4.6.37. 10-[4′-((1,3-Dioxoisoindolin-2-yl)methyl)-1H-1,2,3-triazole-1-yl] 8b-11

80% yield as a white oil; IR (film) 2949, 1711, 1626, 1394, 1084, 712 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.83–7.75 (2H, m, H-Ar), 7.74 (1H, s, H-5′), 7.71–7.64 (2H, m, H-Ar), 7.41 (1H, brs, H-3), 6.26 (1H, brs, OH), 5.69 (1H, brs, H-7), 5.18 (2H, s, CH₂), 5.10–4.94 (2H, m, H-10), 4.84 (1H, d, J = 8.4 Hz, H-1), 3.66 (3H, s, OCH₃), 3.08 (1H, q, J = 8.4 Hz, H-5), 2.83 (1H, dd, J = 16.8, 8.4 Hz, H-6a), 2.38 (1H, t, J = 7.6 Hz, H-9), 2.08–2.01 (1H, m, H-6b); ¹³C NMR (100 MHz, CDCl₃): δ 167.80, 167.73 (2C), 152.74, 142.65, 137.70, 134.17, 132.46 (2C), 131.97, 123.56, 123.51 (2C), 110.31, 96.34, 51.28, 50.45, 47.21, 39.09, 36.07, 32.95, 29.69; HRMS (m/z): calcd for C₂₂H₂₀N₄O₆ [M + H]⁺ 437.1456, found 437.1468.

4.6.38. 10-[4′-(1-Hydroxycyclohexyl)-1H-1,2,3-triazole-1-yl]genipin 8b-12

97% yield as a white solid, mp: 128.6–132.6 °C; IR (film) 3511, 2929, 2855, 1738, 1697, 1444, 1084 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.55 (1H, s, H-5′), 7.46 (1H, brs, H-3), 6.59 (1H, brs, OH), 5.75 (1H, brs, H-7), 5.40–5.10 (2H, m, H-10), 4.82 (1H, d, J = 8.8 Hz, H-1), 3.69 (3H, s, OCH₃), 3.13 (1H, q, J = 8.0 Hz, H-5), 2.87 (1H, dd, J = 15.6, 8.8 Hz, H-6a), 2.41 (1H, t, J = 8.0 Hz, H-9), 2.09–2.04 (1H, m, H-6b), 2.00–1.30 (10H, m, 5×CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 167.80, 155.23, 152.72, 138.03, 132.11, 120.80, 110.11, 96.26, 69.42, 51.18, 50.24, 47.13, 38.94, 37.72, 37.68, 36.02, 29.54, 25.20, 21.82. HRMS (m/z): calcd for C₁₉H₂₅N₃O₅ [M + H]⁺ 376.1872, found 376.1877.

4.6.39. 10-[4′-(1-Hydroxycyclopentyl)-1H-1,2,3-triazole-1-yl]genipin 8b-13

92% yield as a white solid, mp: 128.6–132.6 °C; IR (film) 3310, 2924, 2854, 1737, 1708, 1628, 1438, 1106 cm^–1; ¹H NMR (400 MHz, CDCl₃): δ 7.54 (1H, s, H-5′), 7.50 (1H, brs, H-3), 5.84 (1H, brs, H-7), 5.70 (1H, brs, OH), 5.24 (1H, d, J = 15.6 Hz, H-10a), 5.14 (1H, d, J = 16.0 Hz, H-10b), 4.88–4.79 (1H, m, H-1), 3.71 (3H, s, OCH₃), 3.16 (1H, q, J = 8.4 Hz, H-5), 2.91 (1H, dd, J = 16.8, 8.4 Hz, H-6a), 2.85–2.69 (1H, m, OH), 2.40 (1H, t, J = 8.0 Hz, H-9), 2.14–1.78 (9H, m, H-6b, 4× CH₂); ¹³C NMR (100 MHz, CDCl₃): δ 167.79, 154.20, 152.72, 137.87, 132.72, 120.67, 110.38, 96.41, 78.91, 51.20, 50.26, 47.27, 41.12(2C), 39.07, 36.17, 23.49(2C); HRMS (m/z): calcd for C₁₈H₂₃N₃O₅ [M + Na]⁺ 384.1535, found 384.1543.

Acknowledgments

This work was supported by the Research Unit in Synthetic Compounds and Synthetic Analogues from Natural Product for Drug Discovery (RSND). R.S. and P.S. are grateful for support through the Postdoctoral Fellowship Award from Burapha University. The authors thank Assistant Prof. Suchaya Pongsai, Faculty of Science, Burapha University, for helpful discussions on docking simulation techniques. Special thanks go to Dr Ron Beckett, Faculty of Science, Burapha University, for his comments and English correction.

Glossary

Abbreviations

AD: Alzheimer’s disease
AChE: acetylcholinesterase
BuChE: butyrylcholinesterase
TBSCl: tert-butyldimethylsilyl chloride
Ac₂O: acetic anhydride
TBDPSCl: tert-butyldiphenylsilyl chloride
DCM: dichloromethane
THF: tetrahydrofuran
MsCl: methanesulfonyl chloride
Et₃N: triethylamine
NaN₃: sodium azide
DMF: dimethylformamide
TBAF: tetra-n-butylammonium fluoride
CuI: copper(I)iodide
CH₃CN: acetonitrile
rt: room temperature
H₂O₂: hydrogen peroxide
NA: not active

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.2c01593.

Experimental details and protocols on protein expression and purification, inhibition and binding studies, and X-ray crystallography (PDF)

Author Contributions

All authors have given approval to the final version of the manuscript.

The authors declare no competing financial interest.

Supplementary Material

ao2c01593_si_001.pdf^{(2.7MB, pdf)}

References

Ulrich J. D.; Holtzman D. M. TREM2 Function in Alzheimer’s Disease and Neurodegeneration. ACS Chem. Neurosci. 2016, 7, 420–427. 10.1021/acschemneuro.5b00313. [DOI] [PubMed] [Google Scholar]
WHO, Dementia, 2018. http://www.who.int/news-room/fact-sheets/detail/Dementia, https://www.alz.co.uk/research/WorldAlzheimerReport2016.pdf.
Romero A.; Cacabelos R.; Oset-Gasque M. J.; Samadi A.; Marco-Contelles J. Novel tacrine-related drugs as potential candidates for the treatment of Alzheimer’s disease. Bioorg. Med. Chem. Lett. 2013, 23, 1916–1922. 10.1016/j.bmcl.2013.02.017. [DOI] [PubMed] [Google Scholar]
Guo J.; Wang Z.; Liu R.; Huang Y.; Zhang N.; Zhang R. Memantine, Donepezil, or Combination Therapy-What is the best therapy for Alzheimer’s Disease? A Network Meta-Analysis. Brain Behav. 2020, 10, e01831 10.1002/brb3.1831. [DOI] [PMC free article] [PubMed] [Google Scholar]
Marques L. A.; Maada I.; de Kanter F. J.; Lingeman H.; Irth H.; Niessen W. M.; Giera M. Stability-indicating study of the anti-Alzheimer’s drug galantamine hydrobromide. J. Pharm. Biomed. Anal. 2011, 55, 85–92. 10.1016/j.jpba.2011.01.022. [DOI] [PubMed] [Google Scholar]
Akinyemi A. J.; Oboh G.; Oyeleye S. I.; Ogunsuyi O. Anti-amnestic Effect of Curcumin in Combination with Donepezil, an Anticholinesterase Drug: Involvement of Cholinergic System. Neurotoxic. Res. 2017, 31, 560–569. 10.1007/s12640-017-9701-5. [DOI] [PubMed] [Google Scholar]
Gorman A. M. Neuronal cell death in neurodegenerative diseases: recurring themes around protein handling. J. Cell. Mol. Med. 2008, 12, 2263–2280. 10.1111/j.1582-4934.2008.00402.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
Bartorelli L.; Giraldi C.; Saccardo M.; Cammarata S.; Bottini G.; Fasanaro A. M.; Trequattrini A. Effects of switching from an AChE inhibitor to a dual AChE-BuChE inhibitor in patients with Alzheimer’s disease. Curr. Med. Res. Opin. 2005, 21, 1809–1817. 10.1185/030079905X65655. [DOI] [PubMed] [Google Scholar]
Załuski D.; Kuzniewski R. In Vitro Anti-AChE, Anti-BuChE, and Antioxidant Activity of 12 Extracts of Eleutherococcus Species. Oxid. Med. Cell. Longevity 2016, 2016, 4135135 10.1155/2016/4135135. [DOI] [PMC free article] [PubMed] [Google Scholar]
Contestabile A. The history of the cholinergic hypothesis. Behav. Brain Res. 2011, 221, 334–340. 10.1016/j.bbr.2009.12.044. [DOI] [PubMed] [Google Scholar]
Kamal M. A.; Klein P.; Luo W.; Li Y.; Holloway H. W.; Tweedie D.; Greig N. H. Kinetics of human serum butyrylcholinesterase inhibition by a novel experimental Alzheimer therapeutic, dihydrobenzodioxepine cymserine. Neurochem. Res. 2008, 33, 745–753. 10.1007/s11064-007-9490-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
Marucci G.; Buccioni M.; Ben D. D.; Lambertucci C.; Volpini R.; Amenta F. Efficacy of acetylcholinesterase inhibitors in Alzheimer’s disease. Neuropharmacology 2021, 190, 108352 10.1016/j.neuropharm.2020.108352. [DOI] [PubMed] [Google Scholar]
Darras F. H.; Kling B.; Heilmann J.; Decker M. Neuroprotective Tri- and Tetracyclic BChE Inhibitors Releasing Reversible Inhibitors upon Carbamate Transfer. ACS Med. Chem. Lett. 2012, 3, 914–919. 10.1021/ml3001825. [DOI] [PMC free article] [PubMed] [Google Scholar]
Greig N. H.; Lahiri D. K.; Sambamurti K. Butyrylcholinesterase: an important new target in Alzheimer’s disease therapy. Int. Psychogeriatr. 2002, 14, 77–91. 10.1017/s1041610203008676. [DOI] [PubMed] [Google Scholar]
Yang L.; Peng K.; Zhao S.; Chen L.; Qiu F. Monoterpenoids from the fruit of Gardenia jasminoides Ellis (Rubiaceae). Biochem. Syst. Ecol. 2013, 50, 435–437. 10.1016/j.bse.2013.06.012. [DOI] [Google Scholar]
Lelono R.A.A.; Tachibana S.; Itoh K. Isolation of antifungal compounds from Gardenia jasminoides. Pak. J. Biol. Sci. 2009, 12, 949–956. 10.3923/pjbs.2009.949.956. [DOI] [PubMed] [Google Scholar]
Peng S.-x. M. J.-h.The Role of Genipin and Geniposide in Liver Diseases: A Review Altern. Integr. Med. 201302 10.4172/2327-5162.1000117. [DOI] [Google Scholar]
Yamazaki M.; Sakura N.; Chiba K.; Mohri T. Prevention of the Neurotoxicity of the Amyloid β Protein by Genipin. Biol. Pharm. Bull. 2001, 24, 1454–1455. 10.1248/bpb.24.1454. [DOI] [PubMed] [Google Scholar]
Huang W.; Wang Y.; Li J.; Zhang Y.; Ma X.; Zhu P.; Zhang Y. Design, synthesis, and evaluation of genipin derivatives for the treatment of Alzheimer’s Disease. Chem. Biol. Drug Des. 2019, 93, 110–122. 10.1111/cbdd.13194. [DOI] [PubMed] [Google Scholar]
Kumar S.; Khokra S. L.; Yadav A. Triazole analogues as potential pharmacological agents: a brief review. Future J. Pharm. Sci. 2021, 7, 106 10.1186/s43094-021-00241-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
Baraniak D.; Boryski J. Triazole-Modified Nucleic Acids for the Application in Bioorganic and Medicinal Chemistry. Biomedicines 2021, 9, 628 10.3390/biomedicines9060628. [DOI] [PMC free article] [PubMed] [Google Scholar]
Wang Z. X.; Qin H. L. Regioselective synthesis of 1,2,3-triazole derivatives via 1,3-dipolar cycloaddition reactions in water. Chem. Commun. 2003, 19, 2450–2451. 10.1039/b307084k. [DOI] [PubMed] [Google Scholar]
Moorman R. M.; Collier M. B.; Frohock B. H.; Womble M. D.; Chalker J. M. Halide inhibition of the copper-catalysed azide-alkyne cycloaddition. Org. Biomol. Chem. 2015, 13, 1974–1978. 10.1039/c4ob02479f. [DOI] [PubMed] [Google Scholar]
Silalai P.; Sirion U.; Piyachaturawat P.; Chairoungdua A.; Suksen K.; Saeeng R. Design, Synthesis and Evaluations of New 10-Triazolyl-1-methoxygenipin Analogues for Their Cytotoxicity to Cancer Cells. ChemistrySelect 2020, 5, 9540–9546. 10.1002/slct.202001908. [DOI] [Google Scholar]
Takasu K.; Azuma T.; Enkhtaivan I.; Takemoto Y. Synthesis and properties of chiral thioureas bearing an additional function at a remote position tethered by a 1,5-disubstituted triazole. Molecules 2010, 15, 8327–8348. 10.3390/molecules15118327. [DOI] [PMC free article] [PubMed] [Google Scholar]
Camberlein V.; Kraupner N.; Bou Karroum N.; Lipka E.; Deprez-Poulain R.; Deprez B.; Bosc D. Multi-component reaction for the preparation of 1,5-disubstituted 1,2,3-triazoles by in-situ generation of azides and nickel-catalyzed azide-alkyne cycloaddition. Tetrahedron Lett. 2021, 73, 153131 10.1016/j.tetlet.2021.153131. [DOI] [Google Scholar]
Sooknual P.; Pingaew R.; Phopin K.; Ruankham W.; Prachayasittikul S.; Ruchirawat S.; Prachayasittikul V. Synthesis and neuroprotective effects of novel chalcone-triazole hybrids. Bioorg. Chem. 2020, 105, 104384 10.1016/j.bioorg.2020.104384. [DOI] [PubMed] [Google Scholar]
Li J. C.; Zhang J.; Rodrigues M. C.; Ding D. J.; Longo J. P.; Azevedo R. B.; Muehlmann L. A.; Jiang C. S. Synthesis and evaluation of novel 1,2,3-triazole-based acetylcholinesterase inhibitors with neuroprotective activity. Bioorg. Med. Chem. Lett. 2016, 26, 3881–3885. 10.1016/j.bmcl.2016.07.017. [DOI] [PubMed] [Google Scholar]
Najafi Z.; Mahdavi M.; Saeedi M.; Karimpour-Razkenari E.; Asatouri R.; Vafadarnejad F.; Moghadam F. H.; Khanavi M.; Sharifzadeh M.; Akbarzadeh T. Novel tacrine-1,2,3-triazole hybrids: In vitro, in vivo biological evaluation and docking study of cholinesterase inhibitors. Eur. J. Med. Chem. 2017, 125, 1200–1212. 10.1016/j.ejmech.2016.11.008. [DOI] [PubMed] [Google Scholar]
Chekir S.; Debbabi M.; Regazzetti A.; Dargere D.; Laprevote O.; Ben Jannet H.; Gharbi R. Design, synthesis and biological evaluation of novel 1,2,3-triazole linked coumarinopyrazole conjugates as potent anticholinesterase, anti-5-lipoxygenase, anti-tyrosinase and anti-cancer agents. Bioorg. Chem. 2018, 80, 189–194. 10.1016/j.bioorg.2018.06.005. [DOI] [PubMed] [Google Scholar]
Rayatzadeh A.; Saeedi M.; Mahdavi M.; Rezaei Z.; Sabourian R.; Mosslemin M. H.; Akbarzadeh T.; Foroumadi A.; Shafiee A. Synthesis and evaluation of novel oxoisoindoline derivatives as acetylcholinesterase inhibitors. Monatsh. Chem.—Chem. Mon. 2015, 146, 637–643. 10.1007/s00706-014-1334-2. [DOI] [Google Scholar]

Associated Data

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Supplementary Materials

ao2c01593_si_001.pdf^{(2.7MB, pdf)}

[ref1] Ulrich J. D.; Holtzman D. M. TREM2 Function in Alzheimer’s Disease and Neurodegeneration. ACS Chem. Neurosci. 2016, 7, 420–427. 10.1021/acschemneuro.5b00313. [DOI] [PubMed] [Google Scholar]

[ref2] WHO, Dementia, 2018. http://www.who.int/news-room/fact-sheets/detail/Dementia, https://www.alz.co.uk/research/WorldAlzheimerReport2016.pdf.

[ref3] Romero A.; Cacabelos R.; Oset-Gasque M. J.; Samadi A.; Marco-Contelles J. Novel tacrine-related drugs as potential candidates for the treatment of Alzheimer’s disease. Bioorg. Med. Chem. Lett. 2013, 23, 1916–1922. 10.1016/j.bmcl.2013.02.017. [DOI] [PubMed] [Google Scholar]

[ref4] Guo J.; Wang Z.; Liu R.; Huang Y.; Zhang N.; Zhang R. Memantine, Donepezil, or Combination Therapy-What is the best therapy for Alzheimer’s Disease? A Network Meta-Analysis. Brain Behav. 2020, 10, e01831 10.1002/brb3.1831. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref5] Marques L. A.; Maada I.; de Kanter F. J.; Lingeman H.; Irth H.; Niessen W. M.; Giera M. Stability-indicating study of the anti-Alzheimer’s drug galantamine hydrobromide. J. Pharm. Biomed. Anal. 2011, 55, 85–92. 10.1016/j.jpba.2011.01.022. [DOI] [PubMed] [Google Scholar]

[ref6] Akinyemi A. J.; Oboh G.; Oyeleye S. I.; Ogunsuyi O. Anti-amnestic Effect of Curcumin in Combination with Donepezil, an Anticholinesterase Drug: Involvement of Cholinergic System. Neurotoxic. Res. 2017, 31, 560–569. 10.1007/s12640-017-9701-5. [DOI] [PubMed] [Google Scholar]

[ref7] Gorman A. M. Neuronal cell death in neurodegenerative diseases: recurring themes around protein handling. J. Cell. Mol. Med. 2008, 12, 2263–2280. 10.1111/j.1582-4934.2008.00402.x. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref8] Bartorelli L.; Giraldi C.; Saccardo M.; Cammarata S.; Bottini G.; Fasanaro A. M.; Trequattrini A. Effects of switching from an AChE inhibitor to a dual AChE-BuChE inhibitor in patients with Alzheimer’s disease. Curr. Med. Res. Opin. 2005, 21, 1809–1817. 10.1185/030079905X65655. [DOI] [PubMed] [Google Scholar]

[ref9] Załuski D.; Kuzniewski R. In Vitro Anti-AChE, Anti-BuChE, and Antioxidant Activity of 12 Extracts of Eleutherococcus Species. Oxid. Med. Cell. Longevity 2016, 2016, 4135135 10.1155/2016/4135135. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref10] Contestabile A. The history of the cholinergic hypothesis. Behav. Brain Res. 2011, 221, 334–340. 10.1016/j.bbr.2009.12.044. [DOI] [PubMed] [Google Scholar]

[ref11] Kamal M. A.; Klein P.; Luo W.; Li Y.; Holloway H. W.; Tweedie D.; Greig N. H. Kinetics of human serum butyrylcholinesterase inhibition by a novel experimental Alzheimer therapeutic, dihydrobenzodioxepine cymserine. Neurochem. Res. 2008, 33, 745–753. 10.1007/s11064-007-9490-y. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref12] Marucci G.; Buccioni M.; Ben D. D.; Lambertucci C.; Volpini R.; Amenta F. Efficacy of acetylcholinesterase inhibitors in Alzheimer’s disease. Neuropharmacology 2021, 190, 108352 10.1016/j.neuropharm.2020.108352. [DOI] [PubMed] [Google Scholar]

[ref13] Darras F. H.; Kling B.; Heilmann J.; Decker M. Neuroprotective Tri- and Tetracyclic BChE Inhibitors Releasing Reversible Inhibitors upon Carbamate Transfer. ACS Med. Chem. Lett. 2012, 3, 914–919. 10.1021/ml3001825. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref14] Greig N. H.; Lahiri D. K.; Sambamurti K. Butyrylcholinesterase: an important new target in Alzheimer’s disease therapy. Int. Psychogeriatr. 2002, 14, 77–91. 10.1017/s1041610203008676. [DOI] [PubMed] [Google Scholar]

[ref15] Yang L.; Peng K.; Zhao S.; Chen L.; Qiu F. Monoterpenoids from the fruit of Gardenia jasminoides Ellis (Rubiaceae). Biochem. Syst. Ecol. 2013, 50, 435–437. 10.1016/j.bse.2013.06.012. [DOI] [Google Scholar]

[ref16] Lelono R.A.A.; Tachibana S.; Itoh K. Isolation of antifungal compounds from Gardenia jasminoides. Pak. J. Biol. Sci. 2009, 12, 949–956. 10.3923/pjbs.2009.949.956. [DOI] [PubMed] [Google Scholar]

[ref17] Peng S.-x. M. J.-h.The Role of Genipin and Geniposide in Liver Diseases: A Review Altern. Integr. Med. 201302 10.4172/2327-5162.1000117. [DOI] [Google Scholar]

[ref18] Yamazaki M.; Sakura N.; Chiba K.; Mohri T. Prevention of the Neurotoxicity of the Amyloid β Protein by Genipin. Biol. Pharm. Bull. 2001, 24, 1454–1455. 10.1248/bpb.24.1454. [DOI] [PubMed] [Google Scholar]

[ref19] Huang W.; Wang Y.; Li J.; Zhang Y.; Ma X.; Zhu P.; Zhang Y. Design, synthesis, and evaluation of genipin derivatives for the treatment of Alzheimer’s Disease. Chem. Biol. Drug Des. 2019, 93, 110–122. 10.1111/cbdd.13194. [DOI] [PubMed] [Google Scholar]

[ref20] Kumar S.; Khokra S. L.; Yadav A. Triazole analogues as potential pharmacological agents: a brief review. Future J. Pharm. Sci. 2021, 7, 106 10.1186/s43094-021-00241-3. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref21] Baraniak D.; Boryski J. Triazole-Modified Nucleic Acids for the Application in Bioorganic and Medicinal Chemistry. Biomedicines 2021, 9, 628 10.3390/biomedicines9060628. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref22] Wang Z. X.; Qin H. L. Regioselective synthesis of 1,2,3-triazole derivatives via 1,3-dipolar cycloaddition reactions in water. Chem. Commun. 2003, 19, 2450–2451. 10.1039/b307084k. [DOI] [PubMed] [Google Scholar]

[ref23] Moorman R. M.; Collier M. B.; Frohock B. H.; Womble M. D.; Chalker J. M. Halide inhibition of the copper-catalysed azide-alkyne cycloaddition. Org. Biomol. Chem. 2015, 13, 1974–1978. 10.1039/c4ob02479f. [DOI] [PubMed] [Google Scholar]

[ref24] Silalai P.; Sirion U.; Piyachaturawat P.; Chairoungdua A.; Suksen K.; Saeeng R. Design, Synthesis and Evaluations of New 10-Triazolyl-1-methoxygenipin Analogues for Their Cytotoxicity to Cancer Cells. ChemistrySelect 2020, 5, 9540–9546. 10.1002/slct.202001908. [DOI] [Google Scholar]

[ref25] Takasu K.; Azuma T.; Enkhtaivan I.; Takemoto Y. Synthesis and properties of chiral thioureas bearing an additional function at a remote position tethered by a 1,5-disubstituted triazole. Molecules 2010, 15, 8327–8348. 10.3390/molecules15118327. [DOI] [PMC free article] [PubMed] [Google Scholar]

[ref26] Camberlein V.; Kraupner N.; Bou Karroum N.; Lipka E.; Deprez-Poulain R.; Deprez B.; Bosc D. Multi-component reaction for the preparation of 1,5-disubstituted 1,2,3-triazoles by in-situ generation of azides and nickel-catalyzed azide-alkyne cycloaddition. Tetrahedron Lett. 2021, 73, 153131 10.1016/j.tetlet.2021.153131. [DOI] [Google Scholar]

[ref27] Sooknual P.; Pingaew R.; Phopin K.; Ruankham W.; Prachayasittikul S.; Ruchirawat S.; Prachayasittikul V. Synthesis and neuroprotective effects of novel chalcone-triazole hybrids. Bioorg. Chem. 2020, 105, 104384 10.1016/j.bioorg.2020.104384. [DOI] [PubMed] [Google Scholar]

[ref28] Li J. C.; Zhang J.; Rodrigues M. C.; Ding D. J.; Longo J. P.; Azevedo R. B.; Muehlmann L. A.; Jiang C. S. Synthesis and evaluation of novel 1,2,3-triazole-based acetylcholinesterase inhibitors with neuroprotective activity. Bioorg. Med. Chem. Lett. 2016, 26, 3881–3885. 10.1016/j.bmcl.2016.07.017. [DOI] [PubMed] [Google Scholar]

[ref29] Najafi Z.; Mahdavi M.; Saeedi M.; Karimpour-Razkenari E.; Asatouri R.; Vafadarnejad F.; Moghadam F. H.; Khanavi M.; Sharifzadeh M.; Akbarzadeh T. Novel tacrine-1,2,3-triazole hybrids: In vitro, in vivo biological evaluation and docking study of cholinesterase inhibitors. Eur. J. Med. Chem. 2017, 125, 1200–1212. 10.1016/j.ejmech.2016.11.008. [DOI] [PubMed] [Google Scholar]

[ref30] Chekir S.; Debbabi M.; Regazzetti A.; Dargere D.; Laprevote O.; Ben Jannet H.; Gharbi R. Design, synthesis and biological evaluation of novel 1,2,3-triazole linked coumarinopyrazole conjugates as potent anticholinesterase, anti-5-lipoxygenase, anti-tyrosinase and anti-cancer agents. Bioorg. Chem. 2018, 80, 189–194. 10.1016/j.bioorg.2018.06.005. [DOI] [PubMed] [Google Scholar]

[ref31] Rayatzadeh A.; Saeedi M.; Mahdavi M.; Rezaei Z.; Sabourian R.; Mosslemin M. H.; Akbarzadeh T.; Foroumadi A.; Shafiee A. Synthesis and evaluation of novel oxoisoindoline derivatives as acetylcholinesterase inhibitors. Monatsh. Chem.—Chem. Mon. 2015, 146, 637–643. 10.1007/s00706-014-1334-2. [DOI] [Google Scholar]

PERMALINK

New 1,2,3-Triazole-genipin Analogues and Their Anti-Alzheimer’s Activity

Patamawadee Silalai

Suwichada Jaipea

Jiraporn Tocharus

Anan Athipornchai

Apichart Suksamrarn

Rungnapha Saeeng

Abstract

1. Introduction

Figure 1.

Figure 2.

Figure 3.

Figure 4.

2. Results and Discussion

2.1. Chemistry

Scheme 1. Synthesis of the 10-Triazolylgenipin Analogues 8a and 8b.

Scheme 2. Scope of Alkyne for Synthesis of the 1,2,3-Triazole-genipin Analogues 8a and 8b.

2.2. Biological Evaluations

2.2.1. Neuroprotective Effects of 1,2,3-Triazole-genipin Analogues on the H2O2 Induced Decrease in Cell Viability

Table 1. Neuroprotective Effects of 1,2,3-Triazole-genipin Analogues.

Figure 5.

2.2.2. Cholinesterase Inhibition Assay

Table 2. ChE Inhibitory Activity of 1,2,3-Triazole-genipin Analoguesa.

2.2.3. Kinetic Study for the Inhibition of BuChE

Figure 6.

2.2.4. Docking Study of BuChE

Table 3. Molecular Docking Analysis of BuChE with 1,2,3-Triazole-genipin Analogues 8a-10 and 8b-4a.

Figure 7.

Figure 8.

3. Conclusions

4. Experimental Section

4.1. Synthesis of Compound 2

4.2. Synthesis of Compound 3

4.3. Synthesis of Compound 4

4.4. Synthesis of Compounds 5 and 6

4.5. Synthesis of Compound 7b

4.6. General Procedure for the Preparation of 1,2,3-Triazole-genipin Analogues (8a), (8b)

4.6.1. 10-[4′-Phenyl-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-1

4.6.2. 10-[4′-(4-Methoxypheny)l-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-2

4.6.3. 10-[4′-(4-Fluorophenyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-3

4.6.4. 10-[4′-(6′,6′-Diphenyl-6′-hydroxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-4

4.6.5. 10-[4′-(Benzyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-5

4.6.6. 10-[4′-(4-Methoxybenzyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-6

4.6.7. 10-[4′-(3,4-Dimethoxybenzyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-7

4.6.8. 10-[4′-(N-Methyl-N-benzylamine)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-8

4.6.9. 10-[4′-(7′-Bromoethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-9

4.6.10. 10-[4′-(7′-Hydroxyethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-10

4.6.11. 10-[4′-(7′-Hydroxypropyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-11

4.6.12. 10-[4′-(tert-Butyldiphenylsilyoxylpropyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-12

4.6.13. 10-[4′-(Triisopropysilyoxylpropyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-13

4.6.14. 10-[4′-(tert-Butyldiphenylsilyoxylethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-14

4.6.15. 10-[4′-(tert-Butylsilyoxylethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-15

4.6.16. 10-[4′-(Triphenyloxylmethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-16

4.6.17. 10-[4′-(Octyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-17

4.6.18. 10-[4′-(Dodecyloxymethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-18

4.6.19. 10-[4′-((Undec-10-enyloxy)methy)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-19

4.6.20. 10-[4′-(((Dioxoisoindolin-2-yl)oxy)methyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-20

4.6.21. 10-[4′-((1,3-Dioxoisoindolin-2-yl)methyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-21

4.6.22. 10-[4′-((1,3-Dioxoisoindolin-2-yl)ethyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-22

4.6.23. 10-[4′-((1,3-Dioxoisoindolin-2-yl)propyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-23

4.6.24. 10-[4′-((1,3-Dioxoisoindolin-2-yl)butyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-24

4.6.25. 10-[4′-(1-Hydroxycyclohexyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-25

4.6.26. 10-[4′-(1-Hydroxycyclopentyl)-1H-1,2,3-triazole-1-yl]-1-acetoxygenipin 8a-26

4.6.27. 10-[4′-Phenyl-1H-1,2,3-triazole-1-yl]genipin 8b-1

4.6.28. 10-[4′-(4-Methoxypheny)l-1H-1,2,3-triazole-1-yl]genipin 8b-2

4.6.29. 10-[4′-(4-Fluorophenyl)-1H-1,2,3-triazole-1-yl]genipin 8b-3

4.6.30. 10-[4′-(6′,6′-Diphenyl-6′-hydroxymethyl)-1H-1,2,3-triazole-1-yl]genipin 8b-4

4.6.31. 10-[4′-(tert-Butyldiphenylsilyoxylpropyl)-1H-1,2,3-triazole-1-yl]genipin 8b-5

4.6.32. 10-[4′-(tert-Butyldiphenylsilyoxylpropyl)-1H-1,2,3-triazole-1-yl]genipin 8b-6

4.6.33. 10-[4′-(Octyloxymethyl)-1H-1,2,3-triazole-1-yl]genipin 8b-7

4.6.34. 10-[4′-(Dodecyloxymethyl)-1H-1,2,3-triazole-1-yl]genipin 8b-8

4.6.35. 10-[4′-((Undec-10-enyloxy)methy)-1H-1,2,3-triazole-1-yl]genipin 8b-9

4.6.36. 10-[4′-(((Dioxoisoindolin-2-yl)oxy)methyl)-1H-1,2,3-triazole-1-yl] 8b-10

4.6.37. 10-[4′-((1,3-Dioxoisoindolin-2-yl)methyl)-1H-1,2,3-triazole-1-yl] 8b-11

4.6.38. 10-[4′-(1-Hydroxycyclohexyl)-1H-1,2,3-triazole-1-yl]genipin 8b-12

4.6.39. 10-[4′-(1-Hydroxycyclopentyl)-1H-1,2,3-triazole-1-yl]genipin 8b-13

Acknowledgments

Glossary

Abbreviations

2.2.1. Neuroprotective Effects of 1,2,3-Triazole-genipin Analogues on the H₂O₂ Induced Decrease in Cell Viability

Table 2. ChE Inhibitory Activity of 1,2,3-Triazole-genipin Analogues^a.

Table 3. Molecular Docking Analysis of BuChE with 1,2,3-Triazole-genipin Analogues 8a-10 and 8b-4^a.