Synthesis and biological assessment of KojoTacrines as new agents for Alzheimer's disease therapy.

In view of the multifactorial nature of Alzheimer's disease (AD), multitarget small molecules (MTSM) represent the most potent and attractive therapeutic strategy to design new drugs for Alzheimer's disease therapy. The new MTSM KojoTacrines (KTs) were designed and synthesized by juxtaposition of selected pharmacophoric motifs from kojic acid and tacrine. Among them, 11-amino-2-(hydroxymethyl)-12-(3-methoxyphenyl)-7,9,10,12-tetrahydropyrano [2',3':5,6] pyrano[2,3-b]quinolin-4(8H)-one (KT2d) was identified as less-hepatotoxic than tacrine, at higher concentration, a moderate, but selective human acetylcholinesterase inhibitor (IC50 = 4.52 ± 0.24 µM), as well as an antioxidant agent (TE = 4.79) showing significant neuroprotection against Aß1-40 at 3 µM and 10 µM concentrations. Consequently, KT2d is a potential new hit-ligand for AD therapy for further biological exploration.

Synthesis and biological assessment of racemic benzochromenopyrimidinetriones as promising agents for Alzheimer's disease therapy.

AIM: Due to the complex nature of Alzheimer's disease, there is a renewed search for multitarget directed drugs. RESULTS: This paper describes the synthesis and in vitro biological evaluation of six racemic 13-aryl-2,3,4,13-tetrahydro-1H,12H-benzo[6,7]chromeno[2,3-d]pyrido[1,2-a]pyrimidine-7,12,14-triones (1a-6a), and six racemic 15-aryl-8,9,10,11,12,15-hexahydro-14H-benzo[6',7']chromeno[2',3:4,5] pyr-imido [1,2-a]azepine-5,14,16-triones (1b-6b), showing antioxidant and cholinesterase inhibitory capacity. Among these compounds, 13-phenyl-2,3,4,13-tetrahydro-1H,12H-benzo[6,7]chromeno[2,3-d]pyrido[1,2-a]pyrimidine-7,12,14-trione (1a) is a nonhepatotoxic at 300 µmol/l dose concentration, and a selective EeAChE inhibitor showing good antioxidant power. CONCLUSION: A new family of racemic benzochromenopyrimidinetriones has been investigated for their potential use in the treatment of Alzheimer's disease.

Synthesis, pharmacological assessment, and molecular modeling of 6-chloro-pyridonepezils: new dual AChE inhibitors as potential drugs for the treatment of Alzheimer's disease.

6-Chloro-pyridonepezils are chloropyridine-donepezil hybrids designed by combining the N-benzylpiperidine moiety present in donepezil with the 2-chloropyridine-3,5-dicarbonitrile heterocyclic ring system, both connected by an appropriate polymethylene linker. 6-Chloro-pyridonepezils1-8 were prepared by reaction of 2,6-dichloro-4-phenylpyridine-3,5-dicarbonitrile (13) [or 2,6-dichloropyridine-3,5-dicarbonitrile (14)] with suitable 2-(1-benzylpiperidin-4-yl)alkylamines (9-12). The biological evaluation showed that these new compounds are cholinesterase inhibitors, in the submicromolar range, one of them (6) being a potent hBuChE inhibitor (IC50 = 0.47 ± 0.08 µM). 6-Chloro-pyridonepezils4, 7 and 8 are potent hAChE inhibitors showing IC50 in the 0.013-0.054 µM range. Particularly, 6-chloro-pyridonepezil8 is 625-fold more selective for hAChE than for hBuChE and compared to donepezil is equipotent for the inhibition of hAChE. Molecular modeling investigation on 6-chloro-pyridonepezils4, 6-8 supports its dual AChE inhibitory profile, by binding simultaneously at the catalytic active and at peripheral anionic sites of the enzyme. The in vitro Blood Brain Barrier (BBB) and theoretical ADME analysis of 6-chloro-pyridonepezils1-8 have been carried out. Overall, compound 8, is a permeable potent and selective dual AChEI that can be considered as a good candidate with potential impact for further pharmacological development in Alzheimer's therapy.

Synthesis, pharmacological assessment, and molecular modeling of acetylcholinesterase/butyrylcholinesterase inhibitors: effect against amyloid-ß-induced neurotoxicity.

The synthesis, molecular modeling, and pharmacological analysis of phenoxyalkylamino-4-phenylnicotinates (2-7), phenoxyalkoxybenzylidenemalononitriles (12, 13), pyridonepezils (14-18), and quinolinodonepezils (19-21) are described. Pyridonepezils 15-18 were found to be selective and moderately potent regarding the inhibition of hAChE, whereas quinolinodonepezils 19-21 were found to be poor inhibitors of hAChE. The most potent and selective hAChE inhibitor was ethyl 6-(4-(1-benzylpiperidin-4-yl)butylamino)-5-cyano-2-methyl-4-phenylnicotinate (18) [IC(50) (hAChE) = 0.25 ± 0.02 µM]. Pyridonepezils 15-18 and quinolinodonepezils 20-21 are more potent selective inhibitors of EeAChE than hAChE. The most potent and selective EeAChE inhibitor was ethyl 6-(2-(1-benzylpiperidin-4-yl)ethylamino)-5-cyano-2-methyl-4-phenylnicotinate (16) [IC(50) (EeAChE) = 0.0167 ± 0.0002 µM], which exhibits the same inhibitory potency as donepezil against hAChE. Compounds 2, 7, 13, 17, 18, 35, and 36 significantly prevented the decrease in cell viability caused by Aß(1-42). All compounds were effective in preventing the enhancement of AChE activity induced by Aß(1-42). Compounds 2-7 caused a significant reduction whereas pyridonepezils 17 and 18, and compound 16 also showed some activity. The pyrazolo[3,4-b]quinolines 36 and 38 also prevented the upregulation of AChE induced by Aß(1-42). Compounds 2, 7, 12, 13, 17, 18, and 36 may act as antagonists of voltage sensitive calcium channels, since they significantly prevented the Ca(2+) influx evoked by KCl depolarization. Docking studies show that compounds 16 and 18 adopted different orientations and conformations inside the active-site gorges of hAChE and hBuChE. The structural and energetic features of the 16-AChE and 18-AChE complexes compared to the 16-BuChE and 18-BuChE complexes account for a higher affinity of the ligand toward AChE. The present data indicate that compounds 2, 7, 17, 18, and 36 may represent attractive multipotent molecules for the potential treatment of Alzheimer's disease.

Pyridonepezils, new dual AChE inhibitors as potential drugs for the treatment of Alzheimer's disease: synthesis, biological assessment, and molecular modeling.

The synthesis, biological assessment and molecular modeling of new pyridonepezils1-8, able to inhibit human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBuChE), are described. The new compounds have been designed as hybrids resulting from a conjunctive approach that combines the N-benzylpiperidine moiety, present in donepezil, and the 2-amino-6-chloropyridine heterocyclic ring system, connected by an appropriate polymethylene linker. Compounds 1-8 were prepared by reaction of 2-amino-6-chloro-4-phenylpyridine-3,5-dicarbonitrile (13) [or 2-amino-6-chloropyridine-3,5-dicarbonitrile (14)] with 2-(1-benzylpiperidin-4-yl)alkylamines (9-12). The biological evaluation of molecules 1-8 showed that compounds 1-6 are potent AChE inhibitors, in the submicromolar, while compounds 7 and 8 are on the nanomolar range, the most potent, 2-amino-6-((3-(1-benzylpiperidin-4-yl)propyl)amino)pyridine-3,5-dicarbonitrile (7), showing a IC(50) (hAChE) = 9.4 ± 0.4 nM. Inhibitors 2-8 are permeable as determined in the PAMPA assay. Compared to donepezil, compound 7 is in the same range of inhibitory activity for hAChE, and 703-fold more selective for hAChE than for hBuChE. Molecular modeling investigation on pyridonepezil7 supports its dual AChE inhibitory profile, binding simultaneously at the catalytic active and at peripheral anionic sites of the enzyme. The theoretical ADME analysis of pyridonepezils1-8 has been carried out. Overall, compound 7, a potent and selective dual AChEI, can be considered as a candidate with potential impact for further pharmacological development in Alzheimer's therapy.

Synthesis, biological assessment, and molecular modeling of racemic 7-aryl-9,10,11,12-tetrahydro-7H-benzo[7,8]chromeno[2,3-b]quinolin-8-amines as potential drugs for the treatment of Alzheimer's disease.

The synthesis, pharmacological analysis and molecular modeling of the readily available racemic tacrine analogs 21-30, bearing the 7-aryl-9,10,11,12-tetrahydro-7H-benzo[7,8]chromeno[2,3-b]quinolin-8-amine heterocyclic ring system (II), prepared by Friedländer reaction of 2-amino-4-aryl-4H-benzo[h]chromene-3-carbonitriles (11-20) with cyclohexanone, are described in this paper. Molecules 21-30 are potent and selective inhibitors of hAChE, in the low micromolar range, one of the most potent inhibitors, 4-(8-amino-9,10,11,12-tetrahydro-7H-benzo[7,8]chromeno[2,3-b]quinolin-7-yl)-2-methoxyphenol (25), showing a IC(50) (hAChE) = 0.33 ± 0.04 µM. Kinetic studies of compound 25 proved that this compound is a mixed type inhibitor for EeAChE (K(i) = 81 nM). Accordingly, molecular modeling of inhibitor 25 showed that both enantiomers have two major predicted binding modes at the active and at the peripheral anionic sites of AChE. Inhibitor 25 has an excellent antioxidant profile as determined in the ORAC experiment (1.47 ± 0.10 Trolox equiv). Inhibitors 26-28 and 30 are permeable to BBB as determined in the PAMPA assay. Compared to tacrine, selected compounds 26-28 and 30 showed less hepatic toxicity in HepG2 cells. Moreover, cell viability-related studies in cortical neurons in primary cultures show that compounds 26-28 and 30 (0.1-50 µM) have significant neuroprotective effects against mitochondrial chain blockers-induced cell death, and, unlike tacrine, are not neurotoxic at concentrations lower than 50 µM. It is worth highlighting that compound 27 has the best neuroprotective properties out of all assayed compounds and shows no neurotoxicity. To sum up, these tacrine analogs can be considered as attractive multipotent therapeutic molecules on pharmacological receptors playing key roles in the progress of Alzheimer's disease.

Synthesis and biological assessment of diversely substituted furo[2,3-b]quinolin-4-amine and pyrrolo[2,3-b]quinolin-4-amine derivatives, as novel tacrine analogues.

The synthesis and pharmacological analyses of a number of furo[2,3-b]quinolin-4-amine, and pyrrolo[2,3-b]quinolin-4-amine derivatives are reported. Thus, we synthesized diversely substituted tacrine analogues 1-11 and 12-16 by Friedländer-type reaction of readily available o-amino(furano/pyrrolo)nitriles with suitable and selected cycloalkanones. The biological evaluation of furanotacrines1-11 and pyrrolotacrine13 showed that these are good, in the micromolar range, and highly selective inhibitors of BuChE. In the furanotacrine group, the most interesting inhibitor was 2-(p-tolyl)-5,6,7,8-tetrahydrofuro[2,3-b]quinolin-4-amine (3) [IC(50) (eqBuChE)=2.9 ± 0.4 µM; IC(50) (hBuChE)=119 ± 15 µM]. Conversely, pyrrolotacrines 12 and 14 proved moderately equipotent for both cholinesterases, being 1,2-diphenyl-5,6,7,8-tetrahydro-1H-pyrrolo[2,3-b]quinolin-4-amine (12) the most potent for the inhibition of both enzymes [IC(50) (EeAChE)=0.61 ± 0.04 µM; IC(50) (eqBuChE)=0.074 ± 0.009 µM]. Moreover, pyrrolotacrine 12, at concentrations as low as 300 nM can afford significant neuroprotective effects against Aß-induced toxicity. Docking studies show that compounds 3 and 12 bind in the middle of the AChE active site gorge, but are buried deeper inside BuChE active site gorge, as a consequence of larger BuChE gorge void. All these data suggest that these new tacrine analogues could be used for the potential treatment of Alzheimer's disease.

Synthesis, biological assessment and molecular modeling of new multipotent MAO and cholinesterase inhibitors as potential drugs for the treatment of Alzheimer's disease.

The synthesis, biological evaluation and molecular modeling of new multipotent inhibitors of type I and type II, able to simultaneously inhibit monoamine oxidases (MAO) as well as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), is described. Compounds of type I were prepared by sequential reaction of 2,6-dichloro-4-phenylpyridine-3,5-dicarbonitrile (14) [or 2,6-dichloropyridine-3,5-dicarbonitrile (15)] with prop-2-yn-1-amine (or N-methylprop-2-yn-1-amine) and 2-(1-benzyl-piperidin-4-yl)alkylamines 22-25. Compounds of type II were prepared by Friedländer type reaction of 6-amino-5-formyl-2-(methyl(prop-2-yn-1-yl)amino)nicotinonitriles 32 and 33 with 4-(1-benzylpiperidin-4-yl)butan-2-one (31). The biological evaluation of molecules 1-11 showed that most of these compounds are potent, in the nanomolar range, and selective AChEI, with moderate and equipotent selectivity for MAO-A and MAO-B inhibition. Kinetic studies of compound 8 proved that this is a EeAChE mixed type inhibitor (IC(50) = 16 ± 2; Ki = 12 ± 3 nM). Molecular modeling investigation on compound 8 confirmed its dual AChE inhibitory profile, binding simultaneously at the catalytic active site (CAS) and at the peripheric anionic site (PAS). In overall, compound 11, as a potent and selective dual AChEI, showing a moderate and selective MAO-A inhibitory profile, can be considered as an attractive multipotent drug for further development on two key pharmacological targets playing key roles in the therapy of Alzheimer's disease.