In-vitro and in-silico studies of annelated 1,4,7,8-tetrahydroazocine ester derivatives as nanomolar selective inhibitors of human butyrylcholinesterase.

Based on previous finding showing 2,3,6,11-tetrahydro-1H-azocino[4,5-b]indole as suitable scaffold of novel inhibitors of acetylcholinesterase (AChE), a main target of drugs for the treatment of Alzheimer's disease and related dementias, herein we investigated diverse newly and previously synthesized ß-enamino esters (and ketones) derivatives of 1,4,7,8-tetrahydroazocines (and some azonines) fused with benzene, 1H-indole, 4H-chromen-4-one and pyrimidin-4(3H)-one. Twenty derivatives of diversely annelated eight-to-nine-membered azaheterocyclic ring, prepared through domino reaction of the respective tetrahydropyridine and azepine with activated alkynes, were assayed for the inhibitory activity against AChE and butyrylcholinesterase (BChE). As a major outcome, compound 7c, an alkylamino derivative of tetrahydropyrimido[4,5-d]azocine, was found to be a highly potent BChE-selective inhibitor, which showed a noncompetitive/mixed-type inhibition mechanism against human BChE with single digit nanomolar inhibition constant (Ki = 7.8 ± 0.2 nM). The four-order magnitude BChE-selectivity of 7c clearly reflects the effect of lipophilicity upon binding to the BChE binding cavity. The ChEs' inhibition data, interpreted by chemoinformatic tools and an in-depth in-silico study (molecular docking combined with molecular dynamics calculations), not only highlighted key structural factors enhancing inhibition potency and selectivity toward BChE, but also shed light on subtle differences distinguishing the binding sites of equine BChE from the recombinant human BChE. Compound 7c inhibited P-glycoprotein with IC50 of 0.27 µM, which may support its ability to permeate blood-brain barrier, and proved to be no cytotoxic in human liver cancer cell line (HepG2) at the BChE bioactive concentrations. Overall, the biological profile allows us to envision 7c as a promising template to improve design and development of BChE-selective ligands of pharmaceutical interest, including inhibitors and fluorogenic probes.

Chemical and Biological Evaluation of Novel 1H-Chromeno[3,2-c]pyridine Derivatives as MAO Inhibitors Endowed with Potential Anticancer Activity.

About twenty molecules sharing 1H-chromeno[3,2-c]pyridine as the scaffold and differing in the degree of saturation of the pyridine ring, oxidation at C10, 1-phenylethynyl at C1 and 1H-indol-3-yl fragments at C10, as well as a few small substituents at C6 and C8, were synthesized starting from 1,2,3,4-tetrahydro-2-methylchromeno[3,2-c]pyridin-10-ones (1,2,3,4-THCP-10-ones, 1) or 2,3-dihydro-2-methyl-1H-chromeno[3,2-c]pyridines (2,3-DHPCs, 2). The newly synthesized compounds were tested as inhibitors of the human isoforms of monoamine oxidase (MAO A and B) and cholinesterase (AChE and BChE), and the following main SARs were inferred: (i) The 2,3-DHCP derivatives 2 inhibit MAO A (IC50 about 1 µM) preferentially; (ii) the 1,2,3,4-THCP-10-one 3a, bearing the phenylethynyl fragment at C1, returned as a potent MAO B inhibitor (IC50 0.51 µM) and moderate inhibitor of both ChEs (IC50s 7-8 µM); (iii) the 1H-indol-3-yl fragment at C10 slightly increases the MAO B inhibition potency, with the analog 6c achieving MAO B IC50 of 3.51 µM. The MAO B inhibitor 3a deserves further pharmacological studies as a remedy in the symptomatic treatment of Parkinson's disease and neuroprotectant for Alzheimer's disease. Besides the established neuroprotective effects of MAO inhibitors, the role of MAOs in tumor insurgence and progression has been recently reported. Herein, antiproliferative assays with breast (MCF-7), colon (HCT116) and cisplatin-resistant ovarian (SK-OV-3) tumor cells revealed that the 10-indolyl-bearing 2,3,4,10-THCP analog 6c exerts anti-tumor activity with IC50s in the range 4.83-11.3 µM.

Synthesis of Novel Benzo[b][1,6]naphthyridine Derivatives and Investigation of Their Potential as Scaffolds of MAO Inhibitors.

In this work, 2-alkyl-10-chloro-1,2,3,4-tetrahydrobenzo[b][1,6]naphthyridines were obtained and their reactivity was studied. Novel derivatives of the tricyclic scaffold, including 1-phenylethynyl (5), 1-indol-3-yl (8), and azocino[4,5-b]quinoline (10) derivatives, were synthesized and characterized herein for the first time. Among the newly synthesized derivatives, 5c-h proved to be MAO B inhibitors with potency in the low micromolar range. In particular, the 1-(2-(4-fluorophenyl)ethynyl) analog 5g achieved an IC50 of 1.35 µM, a value close to that of the well-known MAO B inhibitor pargyline.

Scouting around 1,2,3,4-Tetrahydrochromeno[3,2-c]pyridin-10-ones for Single- and Multitarget Ligands Directed towards Relevant Alzheimer's Targets.

A number of 1,2,3,4-tetrahydrochromeno[3,2-c]pyridin-10-one derivatives have been synthesized and screened against different targets involved in the onset and progression of Alzheimer's disease (AD), such as acetyl- and butyrylcholinesterase (AChE and BChE), monoamine oxidases A and B (MAO A and B), aggregation of ß-amyloid (Aß) and reactive oxygen species (ROS) production. Derivatives 1 c, 3 b, 4 and 5 a showed multifaceted profiles of promising anti-AD features and returned well-balanced multitargeting inhibitory activities. Moreover, compound 1 f, a potent and selective human MAO B inhibitor (IC50 =0.89 µM), proved to be a safe neuroprotectant in a human neuroblastoma cell line (SH-SY5Y) by improving viability impaired by Aß1-42 and pro-oxidant insult. Furthermore, structure-activity relationships (SARs) and docking models were derived in order to assist further hit-to-lead optimization stage.

Synthesis, molecular docking, and biological activity of 2-vinyl chromones: Toward selective butyrylcholinesterase inhibitors for potential Alzheimer's disease therapeutics.

We investigated the biological activity of a series of substituted chromeno[3,2-c]pyridines, including compounds previously synthesized by our group and novel compounds whose syntheses are reported here. Tandem transformation of their tetrahydropyridine ring under the action of activated alkynes yielding 2-vinylsubstituted chromones was used to prepare nitrogen-containing derivatives of a biologically active chromone system. The inhibitory activity of these chromone derivatives against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterase (CaE) was investigated using the methods of enzyme kinetics and molecular docking. Antioxidant (antiradical) activity of the compounds was assessed in the ABTS assay. The results demonstrated that a subset of the studied chromone derivatives selectively inhibit BChE but do not exhibit antiradical activity. In addition, the results of molecular docking effectively explained the observed features in the efficacy, selectivity, and mechanism of BChE inhibition by the chromone derivatives.

8H-Chromeno[2',3':4,5]imidazo[2,1-a]isoquinoline.

The title compound, C(18)H(12)N(2)O, comprises two aromatic fragments, viz., imidazo[2,1-a]isoquinoline and benzene, linked by oxygen and methyl-ene bridges. Despite the absence of a common conjugative system within the mol-ecule, it adopts an essentially planar conformation with an r.m.s. deviation of 0. 036 Å. In the crystal, due to this structure, mol-ecules form stacks along the b axis by π⋯π stacking inter-actions, with shortest C⋯C distances in the range 3.340 (4)-3.510 (4) Å. The mol-ecules are bound by inter-molecular C-H⋯O inter-actions within the stacks and C-H⋯π inter-actions between the stacks.

Investigation on the antiplatelet activity of pyrrolo[3,2-c]pyridine-containing compounds.

A series of 4,5,6,7-tetrahydro-1H-pyrrolo[3,2-c]pyridines (THPPs), mostly C(2)-substituted derivatives, and some 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indoles (THPIs) were synthesized and tested in-vitro for their ability to inhibit aggregation of human platelet-rich plasma (PRP) induced by adenosine 5'-diphosphate (ADP) and adrenaline (epinephrine). 5-Benzyl THPP (3), 2-(benzylamino)methyl THPP (5f) and 2-ethyl THPI (6) moderately and dose-dependently inhibited platelet aggregation induced by adrenaline and, to a lesser extent, by ADP. These compounds inhibited the second phase of the PRP aggregation triggered by adrenaline, which largely depends upon thromboxane A(2) production and ADP release. In the adrenaline stimulated aggregation, the THPI derivative 6 was found to be nearly equipotent with aspirin, their IC50 values (concentration effecting 50% inhibition of aggregation) being 90 and 60 microM, respectively. A relation between activity and calculated octanol-water partition coefficient suggested that a log P value around 2.5 should be the optimal lipophilicity value for the activity of THPP-containing compounds.

Cleavage of some annulated tetrahydropyridines under the action of dimethyl acetylene dicarboxylate in protic solvents. New practical route to substituted pyrroles and indoles.

Tetrahydropyrrolo[3,2-c]pyridines and tetrahydropyrido[4,3-b]indoles undergo piperidine ring opening under the action of dimethyl acetylene dicarboxylate in alcohols or in aqueous dioxane, providing beta-(alk)oxy-substituted pyrroles (indoles) in moderate to high yields.