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. 2024 Mar 5;15(6):1206–1218. doi: 10.1021/acschemneuro.3c00800

4-Oxypiperidine Ethers as Multiple Targeting Ligands at Histamine H3 Receptors and Cholinesterases

Beata Michalska †,*, Marek Dzięgielewski †, Justyna Godyń ‡, Tobias Werner §, Marek Bajda ‡, Tadeusz Karcz ∥, Katarzyna Szczepańska ∥,⊥, Holger Stark §, Anna Więckowska ‡, Krzysztof Walczyński †, Marek Staszewski †,*
PMCID: PMC10958501  PMID: 38440987

Abstract

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This study examines the properties of a novel series of 4-oxypiperidines designed and synthesized as histamine H3R antagonists/inverse agonists based on the structural modification of two lead compounds, viz., ADS003 and ADS009. The products are intended to maintain a high affinity for H3R while simultaneously inhibiting AChE or/and BuChE enzymes. Selected compounds were subjected to hH3R radioligand displacement and gpH3R functional assays. Some of the compounds showed nanomolar affinity. The most promising compound in the naphthalene series was ADS031, which contained a benzyl moiety at position 1 of the piperidine ring and displayed 12.5 nM affinity at the hH3R and the highest inhibitory activity against AChE (IC50 = 1.537 μM). Eight compounds showed over 60% eqBuChE inhibition and hence were qualified for the determination of the IC50 value at eqBuChE; their values ranged from 0.559 to 2.655 μM. Therapy based on a multitarget-directed ligand combining H3R antagonism with additional AChE/BuChE inhibitory properties might improve cognitive functions in multifactorial Alzheimer’s disease.

Keywords: histamine H3 receptor, acetylcholinestrase inhibitor, butyrylcholinesterase inhibitor, multiple targeting, polypharmacology, neurodegenerative disease

1. Introduction

It has been more than 40 years since the seminal study by Arrang and co-workers, which demonstrated that histamine inhibits its own synthesis and release from cortical slices of the rat brain via a new histamine receptor that is pharmacologically distinct from both the histamine H1 and H2 receptors.1 The histamine H3 receptor (H3R) was described as a presynaptic autoreceptor involved in the inhibition of histamine secretion in the brain and proved the neurotransmitter function of histamine.2

It was later discovered that H3Rs do not only control histamine release but also, functioning as heteroreceptors, modulate the other neurotransmitter systems,3 e.g., the cholinergic,4,5 dopaminergic,6 noradrenergic,7,8 and serotoninergic9 systems, in both the central and peripheral nervous systems. H3R antagonists/inverse agonists demonstrated diverse pharmacological effects in preclinical and clinical studies, highlighting the importance of various central nervous system (CNS)-related therapeutic applications, including Parkinson’s disease and Alzheimer’s disease (AD),10 narcolepsy,11 obesity,12 dementia, epilepsy, schizophrenia,13 and attention deficit hyperactivity disorder (ADHD).14 Recently, many other CNS-related disorders have also been suggested as candidates for treatment by H3R antagonist/inverse agonist ligands: Tourette syndrome,15 Prader–Willi syndrome,16 depression,17 or autism.18

The most commonly prescribed drugs for the treatment of AD are cholinesterase inhibitors, which improve memory function and delay cognitive decline without altering the underlying pathology.19 However, these drugs show clear limitations concerning both efficacy and tolerability. Their efficacy on cognition enhancement is limited, with the preferred target patient population suffering mild to moderate cognitive impairment.19 From a neurochemical point of view, the decline in cognitive function associated with normal aging, mild cognitive impairment, AD, and related conditions is thought to be caused by a decrease in cortical cholinergic neurotransmission. Such neurotransmission can be improved and enhanced by both AChE/BuChE inhibitors and H3R antagonists, mediated by different neuronal mechanisms. For instance, the learning and memory-facilitating potential of plentiful H3R antagonists have been shown. The etiology stems from their wake-promoting properties in preclinical and clinical studies.20−22 The arousal effect is cumulated with enhanced cortical fast rhythms that correspond to higher brain functions, including alertness, attention, and cognition.21,22 Moreover, H3R antagonists increase the synthesis and release of histamine and its associated memory enhancement. Furthermore, they can increase the release of other neurotransmitters involved in cognition: the prefrontal cortex (acetylcholine, dopamine), anterior cingulate (acetylcholine, dopamine, norepinephrine), and hippocampus (acetylcholine).23−25 This suggests that it may be possible to enhance cholinergic neurotransmission by combining the two activities in a single molecule as a multitargeting approach.26,27 Histamine can control the signaling effects induced by the activation of the cholinergic receptor through the H3R-controlled mechanism, regulating the excitatory effects of acetylcholine.28 H3Rs, modulating the cholinergic system, increase the level of acetylcholine in the synaptic cleft. Two main enzymes hydrolyze acetylcholine: AChE and butyrylcholinesterase (BuChE). AChE is a neuronal enzyme predominantly found in the neuronal cleft of a healthy brain, and its activity decreases when AD occur.29,30 When AChE activity in AD is reduced, AChE and BuChE progression is inverted, denoting the importance of both enzymes in cognitive dysfunction. Dual-acting compounds, inhibiting additionally AChE or BuChE, prolong the survival time of acetylcholine in the neuronal cleft.31,32 Co-administration of a H3R antagonist (MK-3134) and an AChE inhibitor (donepezil) showed a more pronounced, pro-cognitive outcome than the effects of each compound separately.33,34 Dual-acting drugs can be important for the treatment of Alzheimer’s disease due to their lower toxicity, less drug–drug interactions, unified pharmacokinetic profile, and higher efficacy. By acting through H3R in the CNS, they lower peripheral AChE levels and may result in fewer side effects.35 By inhibiting AChE, these compounds may slow the β-amyloid peptide aggregation process promoted by AChE.36

In recent years, there has been the development of a novel class of procognitive dual-acting drugs, that exhibit both H3R antagonism/inverse agonism and inhibition of AChE and/or BuChE. Three such nonimidazole H3R antagonists with additional cholinesterase inhibition are shown in Figure 1.

Figure 1.

Figure 1

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Representative structures of nonimidazole H3R antagonists with an AChE/BuChE inhibitory effect. (a) Data from ref (37). (b) Data from ref (38). (c) Data from ref (39).

Previously, our laboratory has described piperazine,40 guanidine,41 and 4-hydroxpiperidine-based H3R antagonists.42,43 The structure–activity relationship (SAR) of the 4-hydroxpiperidine series found the most potent compounds to be 5-((1-(benzofuran-2-ylmethyl)piperidin-4-yl)oxy)-N-methyl-N-propylpentan-1-amine (ADS003) (pA2 = 8.47, for reference: thioperamide pA2 = 8.67) and 5-((1-benzylpiperidin-4-yl)oxy)-N-methyl-N-propylpentan-1-amine (ADS009) (pA2 = 7.79) (Figure 2).42,43 Further in vivo evaluation of the impact of ADS003 on brain neurotransmitter systems showed its ability to cross the blood–brain barrier and potency at H3R similar to the reference compound, ciproxifan.42

Figure 2.

Figure 2

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Target molecules for this study.

2. Results and Discussion

2.1. Design

In previous studies on 4-hydroxypiperidines, the two ligands ADS003 and ADS009 (Figure 2) were shown to be highly potent antagonists/inverse agonists at the H3R. They were used as lead compounds for the following structural modification: replacement of the flexible five-methylene group chain with a benzene, biphenyl, or naphthalene linker (Figure 2). The idea to replace the flexible alkyl linker with semirigid groups of the lead compounds is consistent with studies that have demonstrated that replacement of the alkyl chain with more rigid moieties results in the formation of higher affinity H3R ligands.42 A moiety with a more restricted conformation may be better fitted to the receptor-binding site due to reduced flexibility (i.e., degrees of freedom).44

In the first step, two compounds were synthesized (ADS021, ADS023; Scheme 1) in which the aliphatic linker was replaced by a benzene ring carrying an N-methyl-N-propylamine group in the para position. Following this, a series of derivatives were synthesized; these contained a methylene linker connected to the oxygen in position 4 of piperidine and a benzene ring carrying an N-methyl-N-propylaminomethyl substituent in the ortho-, meta-, or para-position (ADS027, ADS028, ADS025, ADS026, ADS022, and ADS024, respectively; Scheme 2). Finally, a series containing a biphenyl ring (ADS029, ADS030; Scheme 3) and a naphthalene ring (ADS031, ADS032; Scheme 4) in place of the aliphatic linker was prepared.

Scheme 1. Synthesis of 4-((1-benzylpiperidin-4-yl)oxy)-N-methyl-N-propylaniline (ADS021) and 4-((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)-N-methyl-N-propylaniline (ADS023).

Scheme 1

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Reagents and conditions: (a) 4-(methylamino)phenol hemisulfate salt (1 equiv), di-tert-butyl dicarbonate (1.5 equiv), Et3N (2 equiv), CH3OH, 4 h, rt; (b) 1 (1 equiv), 1-benzyl-4-hydroxypiperidine/1-(benzofuran-2-ylmethyl)piperidin-4-ol (1.3 equiv), diethyl azodicarboxylate (1.3 equiv), triphenylphosphine (1.3 equiv), dry THF, 10 h, 0 °C; (c) 3.1/3.2 (1 equiv), trifluoroacetic acid (25 equiv), CH2Cl2, 12 h, rt; (d) 4.1/4.2 (1 equiv), propionic anhydride (2 equiv), 2 h, 0–10 °C; (e) 5.1/5.2 (1 equiv), LiAlH4 (2 equiv), Et2O, 2 h, reflux.

Scheme 2. Synthesis of ADS022, ADS024, ADS025, ADS026, ADS027, and ADS028.

Scheme 2

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Reagents and conditions: (a) 1-benzyl-4-hydroxypiperidine/1-(benzofuran-2-ylmethyl)piperidin-4-ol (1 equiv), sodium hydride (2 equiv), 15-crown-5 ether (0.1 equiv), 4-(bromomethyl)benzonitrile (1.2 equiv), toluene, 48 h, rt; (b) 8a.1/8b.1/8c.1/8a.2/8b.2/8c.2 (1 equiv), LiAlH4 (2 equiv), Et2O, 3 h, reflux; (c) 9a.1/9b.1/9c.1/9a.2/9b.2/9c.2 (1 equiv), methyl formate (10 equiv), 10 h, rt; (d) 10a.1/10b.1/10c.1/10a.2/10b.2/10c.2 (1 equiv), LiAlH4 (2 equiv), Et2O, 3 h, reflux; (e) 11a.1/11b.1/11c.1/11a.2/11b.2/11c.2 (1 equiv), propionic anhydride (2 equiv), CH2Cl2, 10 h, 0–10 °C; (f) 12a.1/12b.1/12c.1/12a.2/12b.2/12c.2 (1 equiv), LiAlH4 (2 equiv), Et2O, 3 h, reflux.

Scheme 3. Synthesis of N-((4′-(((1-Benzylpiperidin-4-yl)oxy)methyl)-[1,1′-biphenyl]-4-yl)methyl)-N-methylpropan-1-amine (ADS029) and N-((4′-(((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)methyl)-[1,1′-biphenyl]-4-yl)methyl)-N-methylpropan-1-amine (ADS030).

Scheme 3

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Reagents and conditions: 4,4′-bis(chloromethyl)-1,1′-biphenyl (1.2 equiv), sodium hydride (2 equiv), 15-crown-5 ether (0.1 equiv), 1-benzyl-4-hydroxypiperidine or benzofuran-2-yl(4-hydroxypiperidin-1-yl)methanone (1 equiv), toluene, 48 h, rt; (b) 14/15 (1 equiv), K2CO3 (2 equiv), the N-methyl-N-propylamine was added (2 equiv), CH3CN, 12 h, rt; (c) 16 (1 equiv), LiAlH4 (2 equiv), Et2O, 3 h, reflux.

Scheme 4. Synthesis of N-((6-(((1-Benzylpiperidin-4-yl)oxy)methyl)naphthalen-2-yl)methyl)-N-methylpropan-1-amine (ADS031) and N-((6-(((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)methyl)naphthalen-2-yl)methyl)-N-methylpropan-1-amine (ADS032).

Scheme 4

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Reagents and conditions: (a) 17 (1 equiv), Li2CO3 (6 equiv), CH3I (6 equiv), DMF2, 24 h, rt; (b) 18 (1 equiv), LiAlH4 (2 equiv), THF, 24 h, rt; (c) 19 (1 equiv), phosphorus tribromide (1 equiv), CH2Cl2, DMF, 1 h, rt; (d) 20 (1.2 equiv), tert-butyl 4-hydroxypiperidine-1-carboxylate (1 equiv), sodium hydride (2 equiv), 15-crown-5 ether (0.1 equiv), toluene, 48 h, rt; (e) 21 (1 equiv), K2CO3 (2 equiv), N-methyl-N-propylamine (2 equiv), acetone, 24 h, rt; (f) 22 (1 equiv), 4 N HCl in dioxane (10 equiv), CHCl3, 24 h, rt; (g) 23 (1 equiv) and benzaldehyde (1.3 equiv), 1,2-dichloroethane, NaBH(OAc)3 (5 equiv), 24 h, argon atmosphere, rt; (h) 23 (1 equiv), benzofuran-2-carbaldehyde (1.3 equiv), 1,2-dichloroethane, NaBH(OAc)3 (5 equiv), 12 h, argon atmosphere, rt.

2.2. Chemistry

All synthetic procedures are illustrated in Schemes 1–4. To synthesize the compounds presented in all schemes, the following intermediates were prepared: 1-(benzofuran-2-ylmethyl)piperidin-4-ol, tert-butyl-4-hydroxypiperidine-1-carboxylate, benzofuran-2-yl(4-hydroxypiperidin-1-yl)methanone, and benzofuran-2-carbaldehyde (Supporting Information).

To obtain tert-butyl (4-((1-benzylpiperidin-4-yl)oxy)phenyl)(methyl)carbamate (3.1; Scheme 1), commercially available 4-(methylamino)phenol hemisulfate salt (1) was treated with di-tert-butyl dicarbonate in the presence of triethylamine (Scheme 1). Mitsunobu reactions of compound 2 with appropriate alcohol (1-benzyl-4-hydroxypiperidine or 1-(benzofuran-2-ylmethyl)piperidin-4-ol) in the presence of diethyl azodicarboxylate and triphenylphosphine lead to 3.1 and 3.2, respectively. Acidic deprotection of Boc-groups gives products 4.1 and 4.2. Amines (4.1 and 4.2) were treated with an excess of propionic anhydride to give amides 5.1 and 5.2, which were subsequently reduced with LiAlH4 to the final products ADS021 and ADS023.

Etherification of appropriate alcohol (1-benzyl-4-hydroxypiperidine 6.1 or 1-(benzofuran-2-ylmethyl)piperidin-4-ol 6.2) with commercially available nitriles (7a, 7b, 7c) and sodium hydride as well as a catalytic amount of 15-crown-5 led to 8a.1, 8b.1, 8c.1, 8a.2, 8b.2, and 8c.2 (Scheme 2). The amines 9a.1, 9b.1, 9c.1, 9a.2, 9b.2, and 9c.2 were obtained from the nitriles 8a.1, 8b.1, 8c.1, 8a.2, 8b.2, and 8c.2 by reduction with LiAlH4. Formylation of the amines with excess methyl formate yielded the amide derivatives 10a.1, 10b.1, 10c.1, 10a.2, 10b.2, and 10c.2, which were reduced with LiAlH4 to the secondary amines 11a.1, 11b.1, 11c.1, 11a.2, 11b.2, and 11c.2. The secondary amines were treated with excess propionic anhydride, giving the amide derivatives 12a.1, 12b.1, 12c.1, 12a.2, 12b.2, and 12c.2. The amides were reduced with LiAlH4 in dry ethyl ether to the corresponding products ADS027, ADS028, ADS025, ADS026, ADS022, and ADS024.

As illustrated in Scheme 3, etherification of commercially available 4,4′-bis(chloromethyl)-1,1′-biphenyl (13) with appropriate alcohol (1-benzyl-4-hydroxypiperidine or benzofuran-2-yl(4-hydroxypiperidin-1-yl)methanone) with sodium hydride and a catalytic amount of 15-crown-5 leads to 14 and 15. N-alkylation of N-methyl-N-propylamine with 14 or 15 in the presence of potassium carbonate led to the formation of ADS029 and 16. The final ADS030 was obtained by the reduction of amide (16) with LiAlH4.

To synthesize the final compounds presented in Scheme 4, commercially available naphthalene-2,6-dicarboxylic acid (17) was first treated with excess methyl iodide and lithium carbonate to obtain the diester derivative 18 (according to Benito and Meldal45). Following this, 18 was reduced with LiAlH4 to the relevant diol (19).46 Bromination of compound 19 led to derivative 20,46 which was used as a substrate for the etherification process of tert-butyl 4-hydroxypiperidine-1-carboxylate. The obtained ether 21 was treated with N-methyl-N-propylamine in the presence of potassium carbonate, leading to compound 22. Acidic deprotection of Boc-groups from the piperidine moiety yielded 23. Finally, reductive amination of 23 and the corresponding aldehydes (benzaldehyde or benzofuran-2-carbaldehyde) in the presence of sodium triacetoxyborohydride allowed the final compounds ADS031 and ADS032 to be obtained.

All final ADS compounds were converted into their salts of oxalic or fumaric acid.

2.3. Pharmacology

2.3.1. Ex Vivo gpH3R Screening on Isolated Guinea Pig Ileum and hH3R Radioligand Displacement Assays

All newly synthesized compounds were evaluated ex vivo as H3R antagonists/inverse agonists on guinea pig ileum (gpH3R) stimulated electrically for contraction.47 Two of the most active pairs (containing benzyl and benzofuran groups) of compounds ADS022 and ADS024 as well as ADS031 and ADS032, all exceeded a pA2 of 7, were subjected to a radioligand displacement assay in membrane fractions of HEK-293 cells stably expressing human H3R (hH3R).48 The affinity for all compounds is summarized in Table 1.

Table 1. Results of ex vivo gpH3R Screening on the Isolated Guinea Pig Ileum; hH3R Radioligand Displacement Assays; Inhibition of electric eel AChE and equine serum BuChE.

2.3.1.

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a

pA2, Ki, eeAChE%inh. and eqBuChE%inh. are means from at least three independent experiments.

b

IC50 inhibitory concentration of electric eel AChE, mean value ± sem of triplicate independent experiments.

c

IC50 inhibitory concentration of BuChE from equine serum, mean value ± sem of triplicate independent experiments. sem: standard error of the mean, h: human; gp: guinea pig.

In this series, derivatives ADS021 and ADS023 showed the lowest potency (pA2 < 4). The introduction of an additional methylene group between 4-oxypiperidine and the aromatic ring resulted in a significant increase in activity, viz., ADS022 pA2 = 7.42 and ADS024 pA2 = 7.57, carrying the N-methyl-N-propyl-aminomethyl substituent at position 4 of the benzene ring. Those with N-methyl-N-propyl-aminomethyl substituted at position 3 exhibited lowered activity, viz. ADS025 (pA2 = 6.89) and ADS026 (pA2 = 7.03). In addition, by altering the N-methyl-N-propyl-aminomethyl substituent at position 2 of the aromatic ring, synthesized compounds (ADS027 and ADS028) demonstrated a further decrease in activity. By looking at the drug-likeness properties of all compounds calculated in the SwissADME web tool,49 we have observed that only ADS021 of the benzyl derivatives has two H-bond acceptors, while the rest of the benzyl derivatives contain three H-bond acceptors. A similar observation applies to benzofuranyl derivatives, where ADS023 contains three H-bond acceptors while the other benzofuranyl derivatives have four H-bond acceptors. As we show later in the manuscript, the lack of an additional fragment engaged in hydrogen bond formation could be related to the low affinity of AD021 and ADS023. Moreover, both compounds consist of only seven rotatable bonds, while the others have nine or even ten (ADS029 and ADS030), which in this case may make it difficult to fit into the binding site. Anyway, all compounds do not exceed ten rotatable bonds, which is consistent with the drug-likeness Veber assumptions.50

SAR showed that substitution at position 4 of the aromatic ring enhances H3R antagonistic activity. Following this, derivatives with biphenyl and naphthalene linkers in place of the 1,4-disubstituted aromatic ring were synthesized to increase structural rigidity and lipophilicity (Schemes 3 and 4). ADS029 and ADS030 containing the biphenyl linker showed lower affinity to gpH3R than the parent compounds ADS022 and ADS024. Compounds with a naphthalene linker, viz., ADS029 and ADS030, showed slightly higher activity than those with a biphenyl moiety. Among all derivatives, the most potent compound in the benzene series was ADS024, which contained a benzofuranyl substituent at position 1 of the piperidine ring, while the most potent compound in the naphthalene series was ADS031, which contained a benzyl moiety at position 1 of the piperidine ring.

Derivatives with the highest potency at gpH3R (ADS022, ADS024, ADS031, and ADS032) were subjected to the hH3R radioligand displacement assay, which demonstrated a nanomolar affinity among all tested compounds (Table 1). The lowest Ki value (12.5 nM; pKi = 7.90) was observed for ADS031. The benzofuranyl derivative ADS032 showed Ki = 44.1 nM (pKi = 7.36). H3R ligands are known to have a distinct affinity profile and species-dependent pharmacology.51 The affinity toward the guinea pig and human H3R differed, which can be explained by the species-dependent isoforms of the receptor.52,53 Replacement of the 1,4-disubstituted aromatic rings of ADS024 and ADS025 by biphenyl rings leads to a decrease of affinity at gpH3R and violations of some log P values (w log P, m log P, x log P) according to drug-like criteria for a drug candidate described by Muegge, Ghose, or Lipinski.54−56 Results with higher affinities were observed for naphthalene derivatives, including Ki values evaluated at hH3R, but only lead compound ADS031 did not exceed a log P of 6 in all predictive methods. All data determined by the SwissADME web tool can be found in the Supporting Information.

2.3.2. Inhibition of electric eel AChE and equine serum BuChE

All compounds were tested for their ability to inhibit acetylcholinesterase (eeAChE from electric eel) and butyrylcholinesterase (eqBuChE from equine serum) using spectroscopic Ellman’s protocol,57 modified for 96-well microplates. Target compounds were tested at a screening concentration of 10 μM. Four compounds (ADS022, ADS025, ADS029, and ADS031) showed over 60% eeAChE inhibition, and hence the IC50 value was determined. The highest inhibitory activity was demonstrated by compound ADS031 (IC50 = 1.537 μM). Moreover, a comparison of the structures of ADS022, ADS025, ADS029, and ADS031 found their AChE inhibitory activity to increase according to the aromatic moiety, i.e., from benzene through biphenyl to naphthalene derivatives. Eight compounds showed over 60% eqBuChE inhibition and were qualified for the determination of the IC50 value (Table 1). Of these, the IC50 values ranged from 0.559 to 2.655 μM, with the lowest IC50 value (IC50 = 0.559 μM) being observed for ADS021, one of the least active compounds at gpH3R. ADS031 showed micromolar inhibitory activity for both AChE and BuChE enzymes and demonstrated higher inhibitory activity against BuChE (IC50 = 1.353 μM) than AChE (IC50 = 1.537 μM). Selectivity is claimed as a therapeutic advantage, but therapy based on a multitarget-directed ligand combining H3R antagonism with additional AChE/BuChE inhibitory properties might improve cognitive functions in multifactorial Alzheimer’s disease. Nanomolar affinity at H3R of ADS031 and micromolar inhibition of both cholinesterases could be more helpful, as BuChE takes over the task if AChE is inhibited.

2.3.3. H3R Intrinsic Activity

For the lead compound ADS031, intrinsic activity at H3R was tested in HEK293 cells expressing recombinant human receptors using a cAMP accumulation assay. The tested compound was able to counteract (R)-(−)-α-methylhistamine-driven inhibition of cAMP production in forskolin-stimulated cells, which was indicative of its H3R antagonist/inverse agonist properties. The IC50 value obtained in the H3R functional assay was 41.7 ± 8.5 [nM] (Kb = 0.75 ± 0.15 [nM]).

2.4. Molecular Docking Studies

The obtained compounds were docked to the recently published crystal structure of H3R to determine their binding modes.58 The induced fit docking procedure revealed similar arrangements in the receptor binding pocket for all derivatives, although they sometimes differed from one another in observed interactions. They were stretched from an orthosteric binding site where the crucial interaction was found with Asp114 from transmembrane domain TM3 toward the extracellular loop ECL2 (Figure 3). Compound ADS031, which showed the highest affinity to H3R (Ki = 12.5 nM) as well as other compounds with high pA2 values, demonstrated significant interactions within the receptor. The aromatic benzyl or benzofuranyl moiety provided π–π stacking interactions with Trp402. The protonated nitrogen atom from the piperidine ring created a salt bridge with Asp114 and cation–π interactions with Tyr115 and Phe398. The ether oxygen atom could form a hydrogen bond with the hydroxyl group of Tyr115. The second aromatic fragment (benzene, naphthalene, and biphenyl) was engaged in π–π stacking with Phe193 and Tyr189. The terminal protonated amino group formed a salt bridge with Glu395. Contrary to this, compounds with shorter ether linkers, a single-second aromatic ring, and an aromatic nonprotonated amine group, such as ADS021 and ADS023, were characterized by reduced π–π stacking interactions and a lack of a salt bridge, which resulted in low pA2 values (below 4).

Figure 3.

Figure 3

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Predicted binding mode for the compound ADS031 with the highest affinity to the histamine H3 receptor (general view—left panel, 2D interaction diagram—right panel).

3. Conclusions

Among the tested compounds, ADS031 (pA2 = 7.54) and ADS024 (pA2 = 7.57) demonstrated the highest ex vivo potency as antagonist/inverse agonist at the gpH3R. Comparing the obtained pA2 values presented in Table 1, it was found that the ex vivo potency increases when the N-methyl-N-propyl-aminomethyl substituent is present in the para position of the aromatic moiety. In the radioligand displacement binding assay studies at the hH3R, compound ADS031 showed the highest affinity (Ki = 12.5 nM), while the benzofuranyl derivative ADS032 showed a lower nanomolar affinity (Ki = 44.1 nM). The lead compound ADS031 was classified as a potent H3R antagonist/inverse agonist in the cAMP accumulation assay.

Molecular docking studies in the hH3R binding pocket indicate that the lead compound ADS031 creates significant interactions, including π–π stacking interactions between Trp402 for the benzyl moiety, a salt bridge with Asp114, and cation–π interactions with Tyr115 and Phe398 and the protonated nitrogen from the piperidine ring: it also forms a hydrogen bond between the Tyr115 and ether oxygen atoms, and π–π stacking between Phe193 and Tyr189 for the naphthalene fragment.

The inhibitory activity of the novel compounds toward their second target was assessed by an AChE/BuChE spectrophotometric assay. All compounds were tested at a concentration of 10 μM and four of them: ADS022, ADS025, ADS029, and ADS031 demonstrated over 60% inhibition of eeAChE and were hence tested for their IC50 value. Compound ADS031 showed the highest inhibitory activity (IC50 = 1.537 μM).

In contrast, eight compounds were qualified for IC50 testing against eqBuChE. The lowest IC50 value was noticed for ADS021 (IC50 = 0.559 μM), one of the least active compounds against gpH3R, while a lower value was demonstrated by ADS031. The most potent compound in the study toward hH3R (IC50 = 1.353 μM).

Therapy incorporating H3R antagonists with additional AChE/BuChE inhibitory effects may improve cognitive functions in Alzheimer’s disease. Combining two or more pharmacophore motifs in a single molecule is one of the strategies for designing multiple targeting ligands. One of the most popular motifs of AChE inhibitors is tacrine. Analogues of tacrine easily lead to potent AChE inhibitors; however, tarcrine has poor therapeutic efficacy and a high prevalence of detrimental effects. Although our lead compounds do not appear to be more active than the known dual-targeting ligands shown in Figure 1, they represent a good basis for structure optimization and promising pharmacological tools for further biological evaluation. Therefore, the assessment of their pharmacokinetic properties will be the subject of our further studies.

4. Materials and Methods

4.1. Chemistry

The 4-(methylamino)phenol hemisulfate salt, di-tert-butyl dicarbonate, 1-benzyl-4-hydroxypiperidine, triphenylphosphine, trifluoroacetic acid, lithium aluminum hydride, 15-crown-5, methyl formate, 4,4′-bis(chloromethyl)-1,1′-biphenyl, N-methyl-N-propylamine, phosphorus tribromide, NaBH(OAc)3, benzofuran-2-carboxylic acid, thionyl chloride (Sigma-Aldrich, St. Louis, MO, USA), diethyl azodicarboxylate, sodium hydride (60% dispersion in mineral oil) (TCI, Tokyo, Japan), benzaldehyde, piperidin-4-ol, propionic anhydride, 4-(bromomethyl)benzonitrile, 3-(bromomethyl)benzonitrile, 2-(bromomethyl)benzonitrile, naphthalene-2,6-dicarboxylic acid (Alfa Aesar, Ward Hill, Massachusetts, USA), and 4 M HCl in dioxane (Fluorochem, Hadfield, UK) were purchased from commercial suppliers and used without further purification.

Nuclear magnetic resonance spectra, 1H NMR and 13C NMR, were recorded on a Bruker Avance III 600 MHz spectrometer (Bruker, Billerica, MA, USA) in CDCl3 and CD3OD. The 1H NMR spectra were run at 600 MHz, and 13C NMR spectra were run at at 150.95 MHz. The chemical shifts are reported in ppm on scale downfield from tetramethylsilane (TMS) as the internal standard, and the signal patterns are indicated as follows: s = singlet, d = doublet, t = triplet, m = multiplet, and br = broad; the number of protons, and J approximate coupling constant in Hertz. Elemental analyses (C, H, and N) for all compounds were measured in a PerkinElmer Series II CHNS/O Analyzer 2400 (PerkinElmer, Waltham, MA, USA); the results agreed with the theoretical values within ±0.4%. TLC data were obtained with Merck silica gel 60F254 aluminum sheets. Flash column chromatography using silica gel, 60 Å, 50 μm (J. T. Baker B. V.) used the same solvent system as for TLC. All obtained final free bases were treated with a methanolic solution of oxalic acid or fumaric acid, and the salts were precipitated with dry diethyl ether and crystallized twice from ethanol. All oxalic (ADS021, ADS022, ADS023, ADS024, ADS025, ADS026, ADS027, ADS028, ADS029, ADS031, and ADS032) and fumaric (ADS030) acid salts were obtained as white crystalline solids.

4.1.1. General Procedure for the Preparation of Final Compounds

4.1.1.1. General Procedure for the Preparation of Compounds ADS021, ADS022, ADS023, ADS024, ADS025, ADS026, ADS027, ADS028, and ADS030

LiAlH4 (2 equiv) was slowly added to a solution of the corresponding amide (1 equiv) (5.1, 5.2, 12a.1, 12b.1, 12c.1, 12a.2, 12b.2, 12c.2, and 16) in 50 mL of anhydrous diethyl ether. The reaction mixture was stirred at 36 °C for 3 h. After completing the reaction, the mixture was quenched by the dropwise addition of water (8 equiv) and 10% NaOH solution (8 equiv), stirred for 2 h, and then filtered by Celite. The precipitate was discarded. The solvent was removed under vacuum, and the crude product was purified by column chromatography to yield the pure product.

4-((1-Benzylpiperidin-4-yl)oxy)-N-methyl-N-propylaniline (ADS021): (50%): Rf = 0.62 (hexane/EtOAc 1:5); 1H NMR (CDCl3, 600 MHz): δ = 0.90 (t, 3H, J = 7.4, NCH2CH2CH3), 1.53–1.59 (m, 2H, NCH2CH2CH3), 1.75–1.81 (m, 2H, Hpip), 1.92–1.98 (m, 2H, Hpip), 2.22–2.26 (m, 2H, Hpip), 2.72–2.76 (m, 2H, Hpip), 2.85 (s, 3H, NCH3), 3.17 (t, 2H, J = 7.5, NCH2CH2CH3), 3.51 (s, 2H, CH2–C6H5), 4.08–4.13 (m, 1H, Hpip), 6.64 (d, 2H, J = 9.1, HAr), 6.82 (d, 2H, J = 9.1, HAr), 7.22–7.25 (m, 1H, HAr), 7.29–7.33 (m, 4H, HAr); 13C NMR (CDCl3, 150 MHz): δ = 11.78 (NCH2CH2CH3), 20.16 (NCH2CH2CH3), 31.44 (Cpip), 39.07 (NCH3), 51.02 (NCH2CH2CH3), 55.89 (Cpip), 63.28 (CH2C6H5), 74.64 (Cpip), 114.27, 118.40, 127.16, 128.39, 129.31, 138.85, 145.22, 149.10 (CAr).

Anal. Calcd for oxalic salt (C22H30N2O·C2H2O4·H2O): C, 65.88; H, 7.60; N, 6.40. Found: C, 66.51; H, 7.81; N, 6.41; mp 156–157.5 °C.

4-((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)-N-methyl-N-propylaniline (ADS023): (80%): Rf = 0.60 (hexane/EtOAc 1:5); 1H NMR (CDCl3, 600 MHz): δ = 0.90 (t, 3H, J = 7.4, NCH2CH2CH3), 1.52–1.59 (m, 2H, NCH2CH2CH3), 1.80–1.87 (m, 2H, CH2pip), 1.95–2.00 (m, 2H, CH2pip), 2.36–2.41 (m, 2H, CH2pip), 2.79–2.83 (m, 2H, CH2pip), 2.84 (s, 3H, CH3), 3.16 (t, 2H, J = 7.4, NCH2CH2CH3), 3.71 (s, 2H, CH2), 4.10–4.15 (m, 1H, CHpip), 6.58 (s, 1H, CHfuran), 6.64 (d, 2H, J = 9.1, HAr), 6.81 (d, 2H, J = 9.0, HAr), 7.17–7.24 (m, 2H, HAr), 7.47 (d, 1H, J = 8.2, HAr), 7.51 (d, 1H, J = 7.6, HAr); 13C NMR (150 MHz, CDCl3): δ = 11.78 (NCH2CH2CH3), 20.14 (NCH2CH2CH3), 31.18 (Cpip), 39.06 (CH3), 50.84 (Cpip), 55.75 (NCH2CH2CH3), 55.86 (CH2), 74.13 (Cpip), 105.69 (Cfuran), 111.53, 114.23, 118.36, 120.88, 122.83, 124.07, 128.56, 145.22, 148.95, 155.14, 155.31 (CAr).

Anal. Calcd for oxalic salt (C24H30N2O2·2C2H2O4·1.5H2O): C, 57.43; H, 6.37; N, 4.58. Found: C, 57.51; H, 5.86; N, 5.00; mp 121–123 °C.

N-(4-(((1-Benzylpiperidin-4-yl)oxy)methyl)benzyl)-N-methylpropan-1-amine (ADS022): (82%): Rf = 0.43 (CH2Cl2/MeOH/NH3(aq) 8:1:1%); 1H NMR (CDCl3, 600 MHz): δ = 0.89 (t, 3H, J = 7.4, NCH2CH2CH3), 1.49–1.55 (m, 2H, NCH2CH2CH3), 1.65–1.71 (m, 2H, CH2pip), 1.88–1.93 (m, 2H, CH2pip), 2.10–2.16 (m, 2H, CH2pip), 2.17 (s, 3H, CH3), 2.30–2.33 (m, 2H, NCH2CH2CH3), 2.73–2.77 (m, 2H, CH2pip), 3.39–3.43 (m, 1H, CHpip), 3.45 (s, 1H, CH2N), 3.48 (s, 2H, CH2C6H5), 4.52 (s, 2H, OCH2C6H5), 7.22–7.32 (m, 9H, HAr); 13C NMR (150 MHz, CDCl3): δ = 12.06 (NCH2CH2CH3), 20.77 (NCH2CH2CH3), 31.59 (Cpip), 42.44(Cpip), 51.39 (Cpip), 59.72 (NCH2CH2CH3), 62.30 (CH2C6H5), 63.24 (CH2N), 69.77 (O_CH2C6H4), 74.80 (Cpip), 127.13, 127.61, 128.37, 129.24, 129.29, 137.80, 138.78 (CAr).

Anal. Calcd for oxalic salt (C24H34N2O·3C2H2O4·0.5H2O): C, 55.81; H, 6.40; N, 4.34. Found: C, 57.61; H, 6.18; N, 4.29; mp 158–160 °C.

N-(4-(((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)methyl)benzyl)-N-methylpropan-1-amine (ADS024): (80%): Rf = 0.74 (CH2Cl2/MeOH/NH3(aq) 8:1:1%); 1H NMR (CDCl3, 600 MHz): δ = 0.89 (t, 3H, J = 7.3, NCH2CH2CH3), 1.49–1.56 (m, 2H, NCH2CH2CH3), 1.70–1.77 (m, 2H, CH2pip), 1.90–1.95 (m, 2H, CH2pip), 2.18 (s, 3H, CH3), 2.26–2.34 (m, 4H, CH2pip, NCH2CH2CH3), 2.80–2.85 (m, 2H, CH2pip), 3.40–3.45 (m, 1H, CHpip), 3.47 (s, 2H, C6H4CH2N), 3.67 (s, 2H, CH2NC5H9), 4.50 (s, 2H, OCH2C6H4), 6.56 (s, 1H, CHfuran), 7.17–7.20 (m, 2H, CHAr), 7.22–7.25 (m, 2H, CHAr), 7.45–7.52 (m, 2H, CHAr); 13C NMR (150 MHz, CDCl3): δ = 12.03 (NCH2CH2CH3), 20.62 (NCH2CH2CH3), 31.32 (2× CH2pip), 42.31 (CH3), 51.17 (CH2pip), 55.68 (CH2NC5H9), 59.56 (NCH2CH2CH3), 62.13 (C6H4CH2N), 69.75 (OCH2C6H4), 74.18 (CHpip), 105.67 (Cfuran), 111.50, 120.85, 122.81, 124.04, 127.61, 128.54, 129.32, 137.81, 138.37, 155.12 (CAr).

Anal. Calcd for oxalic salt (C26H34N2O2·2C2H2O4·0.5H2O): C, 60.49; H, 6.60; N, 4.70. Found: C, 60.63; H, 6.44; N, 4.63; mp 179.4–181.1 °C.

N-(3-(((1-Benzylpiperidin-4-yl)oxy)methyl)benzyl)-N-methylpropan-1-amine (ADS025): (45%): Rf = 0.71 (CH2Cl2/MeOH/NH3(aq) 8:1:1%); 1H NMR (CDCl3, 600 MHz): δ = 0.89 (t, 3H, J = 7.38, CH3CH2CH2N), 1.49–1.56 (m, 2H, CH3CH2CH2N), 1.64–1.71 (m, 2H, CH2pip), 1.87–1.93 (m, 2H, CH2pip), 2.09–2.15 (m, 2H, CH2pip), 2.17 (s, 3H, CH3), 2.31 (t, 3H, J = 7.44, CH3CH2CH2N), 2.72–2.77 (m, 2H, CH2pip), 3.38–3.43 (m, 1H, CHpip), 3.46 (s, 2H, C6H5CH2), 3.48 (s, 2H, CH2N), 4.52 (s, 2H, OCH2C6H4), 7.20–7.32 (m, 9H, CHAr); 13C NMR (150 MHz, CDCl3): δ = 12.08 (CH3CH2CH2N), 20.73 (CH3CH2CH2N), 31.55 (2× Cpip), 42.49 (CH3), 51.38 (2× Cpip), 59.71 (CH3CH2CH2N), 62.43 (C6H5CH2), 63.20 (CH2N), 69.90 (OCH2C6H4), 74.80 (Cpip), 126.27, 127.10, 128.34, 128.39, 129.26, 138.79 (CAr).

Anal. Calcd for oxalic salt (C24H34N2O·3C2H2O4): C, 56.60; H, 6.33; N, 4.40. Found: C, 56.61; H, 6.42; N, 4.44; mp 176.6–178.2 °C.

N-(3-(((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)methyl)benzyl)-N-methylpropan-1-amine (ADS026): (65%): Rf = 0.59 (CH2Cl2/MeOH/NH3(aq) 8:1:1%); 1H NMR (CDCl3, 600 MHz): δ = 0.89 (t, 3H, J = 7.4, CH3CH2CH2N), 1.49–1.56 (m, 2H, CH3CH2CH2N), 1.71–1.78 (m, 2H, CH2pip), 1.90–1.96 (m, 2H, CH2pip), 2.18 (s, 3H, CH3), 2.24–2.34 (m, 4H, CH2pip, CH3CH2CH2N), 2.79–2.86 (m, 2H, CH2pip), 3.39–3.44 (m, 1H, CHpip), 3.46 (s, 2H, C8H5CH2), 3.68 (s, 2H, CH2N), 4.52 (s, 2H, OCH2C6H4), 6.57 (s, 1H, CHfuran), 7.17–7.29 (m, 6H, CHAr), 7.45–7.54 (m, 2H, CHAr); 13C NMR (CDCl3, 150 MHz): δ = 12.08 (CH3CH2CH2N), 20.69 (CH3CH2CH2N), 31.32 (2× Cpip), 42.46 (CH3), 51.21 (2× Cpip), 55.66 (CH3CH2CH2N), 59.69 (C8H5CH2), 62.40 (CH2N), 69.93 (OCH2C6H4), 74.27 (Cpip), 105.68 (Cfuran), 111.50, 120.84, 122.80, 124.04, 126.33, 128.39, 139.00, 139.46, 155.25 (CAr).

Anal. Calcd for oxalic salt (C26H34N2O2·2C2H2O4·1H2O): C, 59.59; H, 6.67; N, 4.63. Found: C, 59.69; H, 6.52; N, 4.29; mp 187–189 °C.

N-(2-(((1-Benzylpiperidin-4-yl)oxy)methyl)benzyl)-N-methylpropan-1-amine (ADS027): (77%): Rf = 0.34 (CH2Cl2/MeOH/NH3(aq) 8:1:1%); 1H NMR (CDCl3, 600 MHz): δ = 0.87 (t, 3H, J = 7.32, NCH2CH2CH3), 1.46–1.53 (m, 2H, NCH2CH2CH3), 1.66–1.71 (m, 2H, CH2pip), 1.89–1.95 (m, 2H, CH2pip), 2.11–2.17 (m, 5H, CH2pip, CH3), 2.30 (t, 2H, J = 7.26, NCH2CH2CH3), 2.73–2.79 (m, 2H, CH2pip), 3.39–3.44 (m, 1H, CHpip), 3.47 (s, 2H, CH2C6H5), 3.49 (s, 1H, CH2N), 4.65 (s, 2H, OCH2C6H4), 7.20–7.41 (m, 9H, HAr); 13C NMR (CDCl3, 150 MHz): δ = 12.10 (CH3CH2CH2N), 20.27 (CH3CH2CH2N), 31.59 (Cpip 2×), 42.22 (CH3), 51.42 (Cpip 2×), 60.06 and 60.19 (CH2C6H5, CH3CH2CH2N), 63.25 (CH2N), 67.49 (OCH2C6H5), 75.10 (Cpip), 127.12, 128.35, 128.55, 129.30, 130.11, 137.59, 137.96, 138.75 (CAr).

Anal. Calcd for oxalic salt (C24H34N2O·2.5C2H2O4·H2O): C, 57.13; H, 6.78; N, 4.60. Found: C, 57.15; H, 6.45; N, 4.38; mp 176–178 °C.

N-(2-(((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)methyl)benzyl)-N-methylpropan-1-amine (ADS028): (43%): Rf = 0.52 (CH2Cl2/MeOH/NH3(aq) 8:1:1%); 1H NMR (CDCl3, 600 MHz): δ = 0.84–0.90 (m, 3H, NCH2CH2CH3), 1.42–1.53 (m, 2H, NCH2CH2CH3), 1.71–1.79 (m, 2H, CH2pip), 1.92–1.97 (m, 2H, CH2pip), 2.10 (s, 3H, CH3), 2.27–2.32 (m 2H, NCH2CH2CH3), 2.79–2.85 (m, 2H, CH2pip), 3.39–3.44 (m, 1H, CHpip), 3.47 (s, 2H, CH2C8H5O), 3.66 (s, 2H, OCH2C6H4), 4.63 (s, 2H, CH2N), 6.55 (s, 1H, Hfuran), 7.15–7.42 (m, 6H, HAr), 7.45–7.51 (m, 2H, HAr); 13C NMR (CDCl3, 150 MHz): δ = 12.07 (CH3CH2CH2N), 20.70 (CH3CH2CH2N), 31.32 (Cpip 2×), 42.16 (CH3), 51.22 (Cpip 2×), 55.64 (CH2C8H5O), 60.06 (CH3CH2CH2N), 67.46 (CH2N), 70.33 (OCH2C6H4), 74.26 (Cpip), 105.64 (Cfuran), 111.45, 120.79, 122.75, 127.06, 127.32, 128.51, 130.15, 137.57, 155.00.

Anal. Calcd for oxalic salt (C26H34N2O2·2C2H2O4·H2O): C, 59.69; H, 6.52; N, 4.29. Found: C, 59.59; H, 6.67; N, 4.63; mp 156–158 °C.

N-((4′-(((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)methyl)-[1,1′-biphenyl]-4-yl)methyl)-N-methylpropan-1-amine (ADS030): (99%): Rf = 0.56 (CH2Cl2/MeOH/NH3(aq) 8:1:1%); 1H NMR (600 MHz, CDCl3): δ = 0.91 (t, 3H, J = 7.8, CH3CH2CH2N), 1.53–1.58 (m, 2H, CH3CH2CH2N), 1.73–1.78 (m, 2H, CH2pip), 1.92–1.97 (m, 2H, CH2pip), 2.21 (s, 3H, CH3), 2.25–2.33 (m, 2H, CH2pip), 2.35 (t, 2H, J = 7.2, CH3CH2CH2N), 2.79–2.86 (m, 2H, CH2pip), 3.42–3.48 (m, 1H, CHpip), 3.51 (s, 2H, CH2C12H8), 3.67 (s, 2H, CH2C8H5), 4.55 (s, 2H, OCH2), 6,57 (s, 1H, Hfuran), 7.17–7.58 (m, 12H, HAr); 13C NMR (150 MHz, CDCl3): δ = 12.06 (CH3CH2CH2N), 20.71 (CH3CH2CH2N), 31.28 (CH2pip), 42.41 (CH3), 51.12 (CH2pip), 55.63 (CH2C8H5), 59.69 (CH3CH2CH2N), 62.11 (CH2N(CH3)C3H7), 69.57 (OCH2), 74.13(CHpip), 105.65 (CHfuran), 111.47, 120.82, 122.77, 124.01, 127.00, 127.03, 128.08, 128.47, 137.97, 139.67, 140.39, 155.22 (CAr).

Anal. Calcd for fumarate salt (C32H38N2O2·2C4H4O4): C, 67.21; H, 6.49; N, 3.92. Found: C, 67.12; H, 6.19; N, 3.93; mp 167–169 °C.

4.1.1.2. General Procedure for the Preparation of Compound ADS029

To a solution of corresponding chloride (14) (1 equiv) and K2CO3 (2 equiv) in 20.0 mL of acetonitrile, N-methyl-N-propylamine was added (2 equiv). The mixture was stirred at room temperature for 12 h. Water (20 mL) was then added, and the mixture was extracted with dichloromethane (3× 20 mL). The organic layer was dried over Na2SO4, the solvent was removed under vacuum, and the crude product was purified by column chromatography to yield the pure product to give compounds ADS029 as a sticky oil.

N-((4′-(((1-Benzylpiperidin-4-yl)oxy)methyl)-[1,1′-biphenyl]-4-yl)methyl)-N-methylpropan-1-amine (ADS029): (51%): Rf = 0.56 (CHCl3/MeOH 9:1); 1H NMR (CDCl3, 600 MHz): δ = 0.91 (t, 3H, J = 7.32, CH3CH2CH2N), 1.52–1.59 (m, 2H, CH3CH2CH2N), 1.67–1.74 (m, 2H, CH2pip), 1.91–1.97 (m, 2H, CH2pip), 2.13–2.21 (m, 2H, CH2pip), 2.22 (s, 3H, CH3), 2.36 (t, 2H, J = 7.44, CH3CH2CH2N), 2.72–2.80 (m, 2H, CH2pip), 3.43–3.47 (m, 1H, CHpip), 3.51 (s, 2H, CH2C6H5), 3.52 (s, 2H, CH2C12H8), 4.56 (s, 2H, OCH2), 7.20–7.66 (m, 13H, HAr); 13C NMR (150 MHz, CDCl3): δ = 12.10 (CH3CH2CH2N), 20.78 (CH3CH2CH2N), 31.55 (CH2pip), 42.48 (CH3), 51.25 (CH2pip), 59.76 (CH3CH2CH2N), 62.17 (CH2C6H5), 63.23 (CH2N(CH3)C3H7), 69.61 (OCH2), 74.86 (CHpip), 127.05, 127.14, 127.23, 128.14, 128.38, 129.32, 129.64, 138.09, 138.60, 138.76, 139.72, 140.43 (CAr).

Anal. Calcd for oxalic salt (C30H38N2O·3C2H2O4): C, 60.67; H, 6.22; N, 3.93. Found: C, 60.71; H, 6.51; N, 4.18; mp 164–165 °C.

4.1.1.3. General Procedure for the Preparation of Compounds ADS031 and ADS032

To the suspension of N-methyl-N-((6-((piperidin-4-yloxy)methyl)naphthalen-2-yl)methyl)propan-1-amine hydrochloride 23 (1 equiv) and benzofuran-2-carbaldehyde (1.3 equiv) or benzaldehyde (1.3 equiv) in 1,2-dichloroethane (2 mL), NaBH(OAc)3 (5 equiv) was added. The reaction mixture was stirred under an argon atmosphere overnight. After completion of the reaction, DCM (5 mL) and a 5% aq solution of NaHCO3 (10 mL) were added, and the biphasic mixture was stirred for 30 min. The layers were separated, and the aqueous layer was additionally extracted with DCM. The combined organic extracts were then dried over MgSO4, and the solvent was removed in vacuo. The crude products were purified by silica gel-flash column chromatography (eluent CH2Cl2/MeOH, gradient 40:1 to 10:1) to give sticky oils.

N-((6-(((1-Benzylpiperidin-4-yl)oxy)methyl)naphthalen-2-yl)methyl)-N-methylpropan-1-amine (ADS031): (61%): Rf = 0.20 (CH2Cl2/MeOH 8:1); 1H NMR (600 MHz, CDCl3): δ = 0.91 (t, 3H, J = 7.8 Hz, CH3CH2CH2N), 1.52–1.59 (m, 2H, CH3CH2CH2N), 1.67–1.75 (m, 2H, CH2pip), 1.90–1.96 (m, 2H, CH2pip), 2.08–2.16 (m, 2H, CH2pip), 2.21 (s, 3H, CH3), 2.36 (t, 2H, J = 7.8 Hz, CH3CH2CH2N), 2.73–2.79 (m, 2H, CH2pip), 3.42–3.47 (m, 1H, CHpip), 3.48 (s, 2H, C6H5CH2), 3.61 (s, 2H, NCH2), 4.68 (s, 2H, OCH2), 7.21–7.26 (m, 1H, HAr), 7.28–7.32 (m, 4H, HAr), 7.43–7.49 (m, 2H, HAr), 7.69–7.71 (m, 1H, HAr), 7.73–7.79 (m, 3H, HAr); 13C NMR (CDCl3, 150 MHz): δ = 12.10 (CH3CH2CH2N), 20.77 (CH3CH2CH2N), 31.58 (CH2pip), 42.57 (CH3), 51.35 (CH2pip), 59.83 (CH3CH2CH2N), 62.68 (C6H5CH2), 63.21 (NCH2), 69.97 (OCH2), 74.68 (CHpip), 125.96, 126.09, 127.12, 127.49, 127.82, 127.95, 128.10, 128.36, 129.29, 132.75, 133.03, 136.32, 137.15, 138.77 (CAr).

Anal. Calcd for oxalic salt (C28H36N2O·2C2H2O4·0.5H2O): C, 63.46; H, 6.82; N, 4.63. Found: C, 63.51; H, 6.83; N, 4.49; mp 154–156 °C.

N-((6-(((1-(Benzofuran-2-ylmethyl)piperidin-4-yl)oxy)methyl)naphthalen-2-yl)methyl)-N-methylpropan-1-amine (ADS032): (47%): Rf = 0.33 (CH2Cl2/MeOH 8:1); 1H NMR (600 MHz, CDCl3): δ = 0.90 (t, 3H, J = 7.8 Hz, CH3CH2CH2N), 1.52–1.60 (m, 2H, CH3CH2CH2N), 1.74–1.81 (m, 2H, CH2pip), 1.92–1.99 (m, 2H, CH2pip), 2.21 (s, 3H, CH3), 2.24–2.30 (m, 2H, CH2pip), 2.36 (t, 2H, J = 7.8 Hz, CH3CH2CH2N), 2.80–2.87 (m, 2H, CH2pip), 3.43–3.50 (m, 1H, CHpip), 3.61 (s, 2H, C8H5CH2), 3.67 (s, 2H, NCH2), 4.67 (s, 2H, OCH2), 6.57 (s, 1H, CHfuran), 7.17–7.26 (m, 2H, HAr), 7.42–7.53 (m, 4H, HAr), 7.69–7.78 (m, 4H, HAr); 13C NMR (CDCl3, 150 MHz): δ = 12.10 (CH3CH2CH2N), 20.77 (CH3CH2CH2N), 31.34 (CH2pip), 42.58 (CH3), 51.19 (CH2pip), 55.67 (C8H5CH2), 59.83 (CH3CH2CH2N), 62.68 (NCH2), 69.97 (OCH2), 74.08 (CHpip), 105.68 (CHfuran), 111.51, 120.84, 122.81, 124.04, 126.11, 127.83, 127.94, 128.10, 128.12, 128.50, 133.04, 136.22, 137.19, 155.06 (CAr).

Anal. Calcd for oxalic salt (C30H36N2O2·2.5C2H2O4): C, 61.67; H, 6.06; N, 4.11. Found: C, 61.72; H, 6.14; N, 4.08; mp 145–148 °C.

Details of the synthesis of all semiproducts, including NMR spectra, are presented in Supporting Information.

4.2. Biological Activity

The compounds were tested against H3R by an ex vivo assay using isolated guinea pig ileum electrically stimulated to contraction, according to Vollinga et al.47 The pA2-values were calculated according to Arunlakshana and Schild.59 The radioligand-displacement assay was performed in membrane fractions of HEK-293 cells stably expressing hH3R. Cell cultivation and membrane preparation were performed according to Kottke et al.48 The Ki values were calculated from the IC50 values using the Cheng–Prusoff equation.60 The statistical calculations were performed on −log(Ki). The mean values and 95% confidence intervals were transformed to nanomolar concentrations. The inhibitory activities toward AChE and BuChE of novel ADS compounds were assessed in a spectrophotometric Ellman’s assay using electric eel AChE (eeAChE) and equine BuChE (eqBuChE).57 Intracellular cAMP accumulation was measured with a homogeneous TR-FRET immunoassay using the LANCE Ultra cAMP kit (PerkinElmer) and HEK293 cells stably expressing the human histamine H3 receptor.61 A more detailed description of the biological methods is presented in the Supporting Information.

4.3. Molecular Docking Studies

Ligand structures were prepared with LigPrep (Schrodinger Suite) from SMILES strings. Protonation states were predicted with Epik at pH 7.4 ± 0.2. The recently obtained crystal structure of H3R was used for the studies (PDB code: 7F61).58 The binding modes of the analyzed compounds were predicted by the Induced Fit Docking procedure (Schrodinger Suite) based on the standard protocol and the OPLS_2005 force field. The binding site was defined as a box with the center at Asp3.32 and size adjusted to allow docking of ligands with length ≤25 Å. The obtained ligand poses were assessed by IFDScore and GlideScore. The interaction networks were visualized with Maestro (Schrodinger Suite) and PyMOL 0.99rc6 (DeLano Scientific LLC).

Acknowledgments

This study was supported by departmental sources of the Medical University of Lodz grant nos. 503/3-016-01/503-31-001-19-00 (to B.M. and M.S.) and the National Science Center, Poland, granted based on decision 2020/36/C/NZ7/00284 (to K.S.).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acschemneuro.3c00800.

  • Chemical synthesis and NMR spectra; description of the biological methods, including an ex vivo assay for histamine H3R receptor antagonists on guinea pig ileum, an hH3R radioligand displacement binding assay, inhibition of electric eel AChE and equine serum BuChE, and H3R intrinsic activity, and physiochemical parameters determined at the SwissADME web tool (PDF)

Author Contributions

Beata Michalska: conceptualization, synthesis of chemical compounds, ex vivo pharmacological studies on guinea pig ileum (H3R), data analysis, interpretation, elaboration, description of the results, and writing the manuscript. Marek Dzięgielewski: synthesis of the compounds ADS031 and ADS032, commenting of manuscript. Justyna Godyń: inhibition of electric eel AChE and equine serum BuChE assay, data analysis, interpretation, elaboration, and description of the obtained results. Tobias Werner: determination of human histamine H3R affinity of a radioligand binding experiment, data analysis, interpretation, elaboration, and description of the obtained results, commenting on the manuscript. Marek Bajda: molecular docking studies, data analysis, interpretation of the obtained results, visualization, elaboration and description of the results, discussing, and extensive commenting on the manuscript. Tadeusz Karcz: H3R intrinsic activity experiment, data analysis, interpretation, elaboration, and description of the obtained results, discussing and extensive commenting on the manuscript. Katarzyna Szczepańska: H3R intrinsic activity experiment, data analysis, interpretation, elaboration, and description of the obtained results. Holger Stark: coordination of the human histamine H3R affinity at the radioligand binding experiment, interpretation of the obtained results, discussing, and extensive commenting on the manuscript. Anna Więckowska: coordination of the inhibition of electric eel AChE and equine serum BuChE assay, data analysis, interpretation, elaboration, and description of the obtained results. Krzysztof Walczyński: supervision, discussed, and extensively commented on the manuscript. Marek Staszewski: supervision, discussed, extensively commented on the manuscript, and data analysis.

The authors declare no competing financial interest.

Supplementary Material

cn3c00800_si_001.pdf (4.5MB, pdf)

References

  1. Arrang J. M.; Garbarg M.; Schwartz J. C. Auto-Inhibition of Brain Histamine Release Mediated by a Novel Class (H3) of Histamine Receptor. Nature 1983, 302 (5911), 832–837. 10.1038/302832a0. [DOI] [PubMed] [Google Scholar]
  2. Panula P.; Chazot P. L.; Cowart M.; Gutzmer R.; Leurs R.; Liu W. L. S.; Stark H.; Thurmond R. L.; Haas H. L. International Union of Basic and Clinical Pharmacology. XCVIII. Histamine Receptors. Pharmacol. Rev. 2015, 67 (3), 601–655. 10.1124/pr.114.010249. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Schlicker E.; Malinowska B.; Kathmann M.; Göthert M. Modulation of Neurotransmitter Release via Histamine H3 Heteroreceptors. Fundam. Clin. Pharmacol. 1994, 8 (2), 128–137. 10.1111/j.1472-8206.1994.tb00789.x. [DOI] [PubMed] [Google Scholar]
  4. Clapham J.; Kilpatrick G. J. Histamine H3 Receptors Modulate the Release of [3H]-acetylcholine from Slices of Rat Entorhinal Cortex: Evidence for the Possible Existence of H3 Receptor Subtypes. Br. J. Pharmacol. 1992, 107 (4), 919–923. 10.1111/j.1476-5381.1992.tb13386.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Yokotani K.; Murakami Y.; Okada S.; Wang M.; Nakamura K. Histamine H3 Receptor-Mediated Inhibition of Endogenous Acetylcholine Release from the Isolated, Vascularly Perfused Rat Stomach. Eur. J. Pharmacol. 2000, 392 (1–2), 23–29. 10.1016/S0014-2999(00)00085-6. [DOI] [PubMed] [Google Scholar]
  6. Schlicker E.; Fink K.; Detzner M.; Göthert M. Histamine Inhibits Dopamine Release in the Mouse Striatum via Presynaptic H3 Receptors. J. Neural. Transm. 1993, 93 (1), 1–10. 10.1007/BF01244933. [DOI] [PubMed] [Google Scholar]
  7. Schlicker E.; Fink K.; Hinterthaner M.; Göthert M. Inhibition of Noradrenaline Release in the Rat Brain Cortex via Presynaptic H3 Receptors. Naunyn-Schmiedebergs Arch. Pharmakol. 1989, 340 (6), 633–638. 10.1007/BF00717738. [DOI] [PubMed] [Google Scholar]
  8. Blandizzi C.; Tognetti M.; Colucci R.; Tacca M. D. Histamine H3 Receptors Mediate Inhibition of Noradrenaline Release from Intestinal Sympathetic Nerves. Br. J. Pharmacol. 2000, 129 (7), 1387–1396. 10.1038/SJ.BJP.0703194. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Schlicker E.; Betz R.; Göthert M. Histamine H3 Receptor-Mediated Inhibition of Serotonin Release in the Rat Brain Cortex. Naunyn-Schmiedebergs Arch. Pharmakol. 1988, 337 (5), 588–590. 10.1007/BF00182737. [DOI] [PubMed] [Google Scholar]
  10. Witkin J. M.; Nelson D. L. Selective Histamine H3 Receptor Antagonists for Treatment of Cognitive Deficiencies and Other Disorders of the Central Nervous System. Pharmacol. Ther. 2004, 103 (1), 1–20. 10.1016/j.pharmthera.2004.05.001. [DOI] [PubMed] [Google Scholar]
  11. Robin Ganellin C.; Schwartz J. C.; Stark H. Discovery of Pitolisant, the First Marketed Histamine H3-Receptor Inverse Agonist/Antagonist for Treating Narcolepsy. Success. Drug Discovery 2018, 3, 359–381. 10.1002/9783527808694.CH13. [DOI] [Google Scholar]
  12. Takahashi K.; Suwa H.; Ishikawa T.; Kotani H. Targeted Disruption of H3 Receptors Results in Changes in Brain Histamine Tone Leading to an Obese Phenotype. J. Clin. Invest. 2002, 110 (12), 1791–1799. 10.1172/JCI200215784. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Pillot C.; Ortiz J.; Héron A.; Ridray S.; Schwartz J. C.; Arrang J. M. Ciproxifan, a Histamine H3-Receptor Antagonist/Inverse Agonist, Potentiates Neurochemical and Behavioral Effects of Haloperidol in the Rat. J. Neurosci. 2002, 22 (16), 7272–7280. 10.1523/JNEUROSCI.22-16-07272.2002. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Glase S. A.; Robertson D. W.; Wise L. D. Chapter 2. Attention Deficit Hyperactivity Disorder: Pathophysiology and Design of New Treatments. Annu. Rep. Med. Chem. 2002, 37, 11–20. 10.1016/S0065-7743(02)37003-9. [DOI] [Google Scholar]
  15. Rapanelli M.; Pittenger C. Histamine and Histamine Receptors in Tourette Syndrome and Other Neuropsychiatric Conditions. Neuropharmacology 2016, 106, 85–90. 10.1016/j.neuropharm.2015.08.019. [DOI] [PubMed] [Google Scholar]
  16. Pullen L. C.; Picone M.; Tan L.; Johnston C.; Stark H. Cognitive Improvements in Children with Prader-Willi Syndrome Following Pitolisant Treatment-Patient Reports. J. Pediatr. Pharmacol. Therapeut. 2019, 24 (2), 166–171. 10.5863/1551-6776-24.2.166. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Iida T.; Yoshikawa T.; Kárpáti A.; Matsuzawa T.; Kitano H.; Mogi A.; Harada R.; Naganuma F.; Nakamura T.; Yanai K. JNJ10181457, a Histamine H3 Receptor Inverse Agonist, Regulates in Vivo Microglial Functions and Improves Depression-like Behaviours in Mice. Biochem. Biophys. Res. Commun. 2017, 488 (3), 534–540. 10.1016/j.bbrc.2017.05.081. [DOI] [PubMed] [Google Scholar]
  18. Baronio D.; Castro K.; Gonchoroski T.; de Melo G. M.; Nunes G. D. F.; Bambini-Junior V.; Gottfried C.; Riesgo R. Effects of an H3R Antagonist on the Animal Model of Autism Induced by Prenatal Exposure to Valproic Acid. PLoS One 2015, 10 (1), e0116363 10.1371/JOURNAL.PONE.0116363. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Johannsen P. Long-Term Cholinesterase Inhibitor Treatment of Alzheimer’s Disease. CNS Drugs 2004, 18 (12), 757–768. 10.2165/00023210-200418120-00001. [DOI] [PubMed] [Google Scholar]
  20. Dauvilliers Y.; Bassetti C.; Lammers G. J.; Arnulf I.; Mayer G.; Rodenbeck A.; Lehert P.; Ding C. L.; Lecomte J. M.; Schwartz J. C. Pitolisant versus Placebo or Modafinil in Patients with Narcolepsy: A Double-Blind, Randomised Trial. Lancet Neurol. 2013, 12 (11), 1068–1075. 10.1016/S1474-4422(13)70225-4. [DOI] [PubMed] [Google Scholar]
  21. Lin J. S.; Sergeeva O. A.; Haas H. L. Histamine H3 Receptors and Sleep-Wake Regulation. J. Pharmacol. Exp. Ther. 2011, 336 (1), 17–23. 10.1124/jpet.110.170134. [DOI] [PubMed] [Google Scholar]
  22. Passani M. B.; Lin J. S.; Hancock A.; Crochet S.; Blandina P. The Histamine H3 Receptor as a Novel Therapeutic Target for Cognitive and Sleep Disorders. Trends Pharmacol. Sci. 2004, 25 (12), 618–625. 10.1016/j.tips.2004.10.003. [DOI] [PubMed] [Google Scholar]
  23. Mochizuki T.; Okakura-Mochizuki K.; Horii A.; Yamamoto Y.; Yamatodani A. Histaminergic Modulation of Hippocampal Acetylcholine Release in Vivo. J. Neurochem. 1994, 62 (6), 2275–2282. 10.1046/j.1471-4159.1994.62062275.x. [DOI] [PubMed] [Google Scholar]
  24. Fox G. B.; Esbenshade T. A.; Pan J. B.; Radek R. J.; Krueger K. M.; Yao B. B.; Browman K. E.; Buckley M. J.; Ballard M. E.; Komater V. A.; Miner H.; Zhang M.; Faghih R.; Rueter L. E.; Bitner R. S.; Drescher K. U.; Wetter J.; Marsh K.; Lemaire M.; Porsolt R. D.; Bennani Y. L.; Sullivan J. P.; Cowart M. D.; Decker M. W.; Hancock A. A. Pharmacological Properties of ABT-239 [4-(2-{2-[(2R)-2-Methylpyrrolidinyl]Ethyl}-Benzofuran-5-Yl)Benzonitrile]: II. Neurophysiological Characterization and Broad Preclinical Efficacy in Cognition and Schizophrenia of a Potent and Selective Histamine H3 Receptor Antagonist. J. Pharmacol. Exp. Ther. 2005, 313 (1), 176–190. 10.1124/jpet.104.078402. [DOI] [PubMed] [Google Scholar]
  25. Medhurst A. D.; Atkins A. R.; Beresford I. J.; Brackenborough K.; Briggs M. A.; Calver A. R.; Cilia J.; Cluderay J. E.; Crook B.; Davis J. B.; Davis R. K.; Davis R. P.; Dawson L. A.; Foley A. G.; Gartlon J.; Gonzalez M. I.; Heslop T.; Hirst W. D.; Jennings C.; Jones D. N. C.; Lacroix L. P.; Martyn A.; Ociepka S.; Ray A.; Regan C. M.; Roberts J. C.; Schogger J.; Southam E.; Stean T. O.; Trail B. K.; Upton N.; Wadsworth G.; Wald J. A.; White T.; Witherington J.; Woolley M. L.; Worby A.; Wilson D. M. GSK189254, a Novel H3 Receptor Antagonist That Binds to Histamine H3 Receptors in Alzheimer’s Disease Brain and Improves Cognitive Performance in Preclinical Models. J. Pharmacol. Exp. Ther. 2007, 321 (3), 1032–1045. 10.1124/jpet.107.120311. [DOI] [PubMed] [Google Scholar]
  26. Proschak E.; Stark H.; Merk D. Polypharmacology by Design: A Medicinal Chemist’s Perspective on Multitargeting Compounds. J. Med. Chem. 2019, 62 (2), 420–444. 10.1021/acs.jmedchem.8b00760. [DOI] [PubMed] [Google Scholar]
  27. Khanfar M. A.; Affini A.; Lutsenko K.; Nikolic K.; Butini S.; Stark H. Multiple Targeting Approaches on Histamine H3 Receptor Antagonists. Front. Neurosci. 2016, 10 (MAY), 201. 10.3389/fnins.2016.00201. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Lopes F. B.; Aranha C. M. S. Q.; Fernandes J. P. S. Histamine H3 Receptor and Cholinesterases as Synergistic Targets for Cognitive Decline: Strategies to the Rational Design of Multitarget Ligands. Chem. Biol. Drug Des. 2021, 98 (2), 212–225. 10.1111/cbdd.13866. [DOI] [PubMed] [Google Scholar]
  29. Kilic B.; Gulcan H. O.; Aksakal F.; Ercetin T.; Oruklu N.; Umit Bagriacik E.; Dogruer D. S. Design and Synthesis of Some New Carboxamide and Propanamide Derivatives Bearing Phenylpyridazine as a Core Ring and the Investigation of Their Inhibitory Potential on In-Vitro Acetylcholinesterase and Butyrylcholinesterase. Bioorg. Chem. 2018, 79, 235–249. 10.1016/j.bioorg.2018.05.006. [DOI] [PubMed] [Google Scholar]
  30. Brus B.; Košak U.; Turk S.; Pišlar A.; Coquelle N.; Kos J.; Stojan J.; Colletier J. P.; Gobec S. Discovery, Biological Evaluation, and Crystal Structure of a Novel Nanomolar Selective Butyrylcholinesterase Inhibitor. J. Med. Chem. 2014, 57 (19), 8167–8179. 10.1021/jm501195e. [DOI] [PubMed] [Google Scholar]
  31. Li B.; Duysen E. G.; Carlson M.; Lockridge O. The Butyrylcholinesterase Knockout Mouse as a Model for Human Butyrylcholinesterase Deficiency. J. Pharmacol. Exp. Ther. 2008, 324 (3), 1146–1154. 10.1124/jpet.107.133330. [DOI] [PubMed] [Google Scholar]
  32. Holmes C.; Ballard C.; Lehmann D.; Smith A. D.; Beaumont H.; Day I. N.; Khan M. N.; Lovestone S.; McCulley M.; Morris C. M.; Munoz D. G.; O’Brien K.; Russ C.; Del Ser T.; Warden D. Rate of Progression of Cognitive Decline in Alzheimer’s Disease: Effect of Butyrylcholinesterase K Gene Variation. J. Neurol. Neurosurg. Psychiatr. 2005, 76 (5), 640–643. 10.1136/jnnp.2004.039321. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Cho W.; Maruff P.; Connell J.; Gargano C.; Calder N.; Doran S.; Fox-Bosetti S.; Hassan A.; Renger J.; Herman G.; Lines C.; Verma A. Additive Effects of a Cholinesterase Inhibitor and a Histamine Inverse Agonist on Scopolamine Deficits in Humans. Psychopharmacology 2011, 218 (3), 513–524. 10.1007/s00213-011-2344-y. [DOI] [PubMed] [Google Scholar]
  34. Łażewska D.; Jończyk J.; Bajda M.; Szałaj N.; Więckowska A.; Panek D.; Moore C.; Kuder K.; Malawska B.; Kieć-Kononowicz K. Cholinesterase Inhibitory Activity of Chlorophenoxy Derivatives—Histamine H3 Receptor Ligands. Bioorg. Med. Chem. Lett. 2016, 26 (16), 4140–4145. 10.1016/j.bmcl.2016.04.054. [DOI] [PubMed] [Google Scholar]
  35. Bembenek S. D.; Keith J. M.; Letavic M. A.; Apodaca R.; Barbier A. J.; Dvorak L.; Aluisio L.; Miller K. L.; Lovenberg T. W.; Carruthers N. I. Lead Identification of Acetylcholinesterase Inhibitors-Histamine H3 Receptor Antagonists from Molecular Modeling. Bioorg. Med. Chem. 2008, 16 (6), 2968–2973. 10.1016/j.bmc.2007.12.048. [DOI] [PubMed] [Google Scholar]
  36. Dorronsoro I.; Castro A.; Martinez A. Peripheral and Dual Binding Site Inhibitors of Acetylcholinesterase as Neurodegenerative Disease Modifying Agents. Expert Opin. Ther. Pat. 2003, 13 (11), 1725–1732. 10.1517/13543776.13.11.1725. [DOI] [Google Scholar]
  37. Morini G.; Comini M.; Rivara M.; Rivara S.; Bordi F.; Plazzi P. V.; Flammini L.; Saccani F.; Bertoni S.; Ballabeni V.; Barocelli E.; Mor M. Synthesis and Structure-Activity Relationships for Biphenyl H3 Receptor Antagonists with Moderate Anti-Cholinesterase Activity. Bioorg. Med. Chem. 2008, 16 (23), 9911–9924. 10.1016/j.bmc.2008.10.029. [DOI] [PubMed] [Google Scholar]
  38. Darras F. H.; Pockes S.; Huang G.; Wehle S.; Strasser A.; Wittmann H. J.; Nimczick M.; Sotriffer C. A.; Decker M. Synthesis, Biological Evaluation, and Computational Studies of Tri- and Tetracyclic Nitrogen-Bridgehead Compounds as Potent Dual-Acting AChE Inhibitors and HH3 Receptor Antagonists. ACS Chem. Neurosci. 2014, 5 (3), 225–242. 10.1021/cn4002126. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Petroianu G.; Arafat K.; Sasse B. C.; Stark H. Multiple Enzyme Inhibitions by Histamine H3 Receptor Antagonists as Potential Procognitive Agents. Pharmazie 2006, 61, 179. [PubMed] [Google Scholar]
  40. Staszewski M.; Walczyński K. 1-Phenoxyalkyl-4-[(N,N-Disubstitutedamino)Alkyl]Piperazine Derivatives as Non-Imidazole Histamine H3-Antagonists. Med. Chem. Res. 2013, 22 (3), 1287–1304. 10.1007/s00044-012-0090-2. [DOI] [Google Scholar]
  41. Staszewski M.; Iwan M.; Werner T.; Bajda M.; Godyń J.; Latacz G.; Korga-Plewko A.; Kubik J.; Szałaj N.; Stark H.; Malawska B.; Więckowska A.; Walczyński K. Guanidines: Synthesis of Novel Histamine H3R Antagonists with Additional Breast Anticancer Activity and Cholinesterases Inhibitory Effect. Pharmaceuticals 2023, 16 (5), 675. 10.3390/ph16050675. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Olszewska B.; Stasiak A.; McNaught Flores D.; Fogel W. A.; Leurs R.; Walczyński K. 4-Hydroxypiperidines and Their Flexible 3-(Amino)Propyloxy Analogues as Non-Imidazole Histamine H3 Receptor Antagonist: Further Structure-Activity Relationship Exploration and in Vitro and in Vivo Pharmacological Evaluation. Int. J. Mol. Sci. 2018, 19 (4), 1243–1261. 10.3390/ijms19041243. [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. Masłowska-Lipowicz I.; Walczyński K. Structure-Activity Relationships of New 1-Substitutedmethyl-4-[5-(N-Methyl-N-Propylamino)Pentyloxy]Piperidines and Selected 1-[(N-Substituted-N-Methyl)-3-Propyloxy]-5-(N-Methy-l-N-Propyl)-Pentanediamines as H3-Antagonists. Chem. Biol. Drug Des. 2014, 83 (1), 106–118. 10.1111/cbdd.12206. [DOI] [PubMed] [Google Scholar]
  44. Jończyk J.; Malawska B.; Bajda M. Hybrid Approach to Structure Modeling of the Histamine H3 Receptor: Multi-Level Assessment as a Tool for Model Verification. PLoS One 2017, 12 (10), e0186108 10.1371/journal.pone.0186108. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Benito J. M.; Meldal M. Bicyclic Organo-Peptides as Selective Carbohydrate Receptors: Design, Solid-Phase Synthesis, and on-Bead Binding Capability. QSAR Comb. Sci. 2004, 23 (2–3), 117–129. 10.1002/qsar.200320011. [DOI] [Google Scholar]
  46. Łukasik B.; Milczarek J.; Pawlowska R.; Żurawiński R.; Chworos A. Facile Synthesis of Fluorescent Distyrylnaphthalene Derivatives for Bioapplications. New J. Chem. 2017, 41 (15), 6977–6980. 10.1039/C7NJ00004A. [DOI] [Google Scholar]
  47. Vollinga R. C.; Zuiderveld O. P.; Scheerens H.; Bast A.; Timmerman H. A Simple and Rapid in Vitro Test System for the Screening of Histamine H3 Ligands. Methods Find Exp. Clin. Pharmacol. 1992, 14, 747–751. [PubMed] [Google Scholar]
  48. Kottke T.; Sander K.; Weizel L.; Schneider E. H.; Seifert R.; Stark H. Receptor-Specific Functional Efficacies of Alkyl Imidazoles as Dual Histamine H3/H4 Receptor Ligands. Eur. J. Pharmacol. 2011, 654 (3), 200–208. 10.1016/j.ejphar.2010.12.033. [DOI] [PubMed] [Google Scholar]
  49. Daina A.; Michielin O.; Zoete V. SwissADME: A Free Web Tool to Evaluate Pharmacokinetics, Drug-Likeness and Medicinal Chemistry Friendliness of Small Molecules. Sci. Rep. 2017, 7 (1), 42717–42813. 10.1038/srep42717. [DOI] [PMC free article] [PubMed] [Google Scholar]
  50. Veber D. F.; Johnson S. R.; Cheng H. Y.; Smith B. R.; Ward K. W.; Kopple K. D. Molecular Properties That Influence the Oral Bioavailability of Drug Candidates. J. Med. Chem. 2002, 45 (12), 2615–2623. 10.1021/jm020017n. [DOI] [PubMed] [Google Scholar]
  51. Stark H.; Sippl W.; Ligneau X.; Arrang J. M.; Ganellin C. R.; Schwartz J. C.; Schunack W. Different Antagonist Binding Properties of Human and Rat Histamine H3 Receptors. Bioorg. Med. Chem. Lett. 2001, 11 (7), 951–954. 10.1016/S0960-894X(01)00090-7. [DOI] [PubMed] [Google Scholar]
  52. Nieto-Alamilla G.; Márquez-Gómez R.; García-Gálvez A. M.; Morales-Figueroa G. E.; Arias-Montaño J. A. The Histamine H3 Receptor: Structure, Pharmacology, and Function. Mol. Pharmacol. 2016, 90, 649–673. 10.1124/mol.116.104752. [DOI] [PubMed] [Google Scholar]
  53. Hancock A. A.; Esbenshade T. A.; Krueger K. M.; Yao B. B. Genetic and Pharmacological Aspects of Histamine H3 Receptor Heterogeneity. Life Sci. 2003, 73 (24), 3043–3072. 10.1016/j.lfs.2003.06.003. [DOI] [PubMed] [Google Scholar]
  54. Muegge I.; Heald S. L.; Brittelli D. Simple Selection Criteria for Drug-like Chemical Matter. J. Med. Chem. 2001, 44 (12), 1841–1846. 10.1021/jm015507e. [DOI] [PubMed] [Google Scholar]
  55. Ghose A. K.; Viswanadhan V. N.; Wendoloski J. J. A Knowledge-Based Approach in Designing Combinatorial or Medicinal Chemistry Libraries for Drug Discovery. 1. A Qualitative and Quantitative Characterization of Known Drug Databases. J. Comb. Chem. 1999, 1 (1), 55–68. 10.1021/cc9800071. [DOI] [PubMed] [Google Scholar]
  56. Lipinski C. A.; Lombardo F.; Dominy B. W.; Feeney P. J. Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings 1PII of original article: S0169-409X(96)00423-1. The article was originally published in Advanced Drug Delivery Reviews 23 (1997) 3–25. 1. Adv. Drug Deliv. Rev. 2001, 46 (1–3), 3–26. 10.1016/S0169-409X(00)00129-0. [DOI] [PubMed] [Google Scholar]
  57. Ellman G. L.; Courtney K. D.; Andres V.; Featherstone R. M. A New and Rapid Colorimetric Determination of Acetylcholinesterase Activity. Biochem. Pharmacol. 1961, 7 (2), 88–95. 10.1016/0006-2952(61)90145-9. [DOI] [PubMed] [Google Scholar]
  58. Peng X.; Yang L.; Liu Z.; Lou S.; Mei S.; Li M.; Chen Z.; Zhang H. Structural Basis for Recognition of Antihistamine Drug by Human Histamine Receptor. Nat. Commun. 2022, 13 (1), 6105–6109. 10.1038/s41467-022-33880-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Arunlakshana O.; Schild H. O. Some Quantitative Uses Of Drug Antagonists. Br. J. Pharmacol. Chemother. 1959, 14 (1), 48–58. 10.1111/j.1476-5381.1959.tb00928.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  60. Yung-Chi C.; Prusoff W. H. Relationship between the Inhibition Constant (KI) and the Concentration of Inhibitor Which Causes 50 per Cent Inhibition (I50) of an Enzymatic Reaction. Biochem. Pharmacol. 1973, 22 (23), 3099–3108. 10.1016/0006-2952(73)90196-2. [DOI] [PubMed] [Google Scholar]
  61. Leff P.; Dougall I. G. Further Concerns over Cheng-Prusoff Analysis. Trends Pharmacol. Sci. 1993, 14 (4), 110–112. 10.1016/0165-6147(93)90080-4. [DOI] [PubMed] [Google Scholar]

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