Synthesis and structure-activity relationship (SAR) of (5,7-disubstituted 3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methylamines as potent serotonin 5-HT(6) receptor (5-HT(6)R) antagonists.

Syntheses, biological evaluation as 5-HT(6) receptor (5-HT(6)R) antagonists, and structure-activity relationships for a series of novel 5,7-disubstituted (3-arylsulfonyl-pyrazolo[1,5-a]pyrimidins are disclosed. The molecule conformational flexibility in the series is restricted by formation of the intramolecular hydrogen bond between 3-sulfo and 2-methylamino groups, which renders high potency and high selectivity to block serotonin-induced responses in HEK-293 cells stably expressing human 5-HT(6)R. In this work, we tested the hypothesis if addition of a positively ionizable group (PI) to the pyrimidine ring of the scaffold members in positions 5, 6, or 7 could further increase their 5HT(6)R blocking potency. We show that the presence of the PI group with small substituents does not substantially affect either potency or selectivity of the ligands while causing substantial changes in their cLogP values. This provides a possibility for designing of the 5HT(6)R ligands with modified ADME characteristics without grossly affecting efficiency of their interaction with the receptor. In respect to the structure-activity relationship (SAR), among other physiochemical parameters, only the molecule size and shape (described by gyration radii) showed a clear tendency for more compact molecules to be more potent antagonists of this receptor.

Synthesis and biological study of 3-(phenylsulfonyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidines as potent and selective serotonin 5-HT6 receptor antagonists.

A number of 3-(phenylsulfonyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidines were prepared and their 5-HT6 receptor binding affinity and ability to inhibit the functional cellular responses to serotonin were evaluated. 3-[(3-chlorophenyl)sulfonyl]-N-(tetrahydrofuran-2-ylmethyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidin-5-amine 2{5,26} appeared to be the most active in a functional assay (IC50=29.0 nM) and 3-(phenylsulfonyl)-N-(2-thienylmethyl) thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidin-5-amine 2{1,28} demonstrated the greatest affinity in a 5-HT6 receptor radioligand binding assay (Ki=1.7 nM). A screening of 5-HT2A and 5-HT2B receptor affinity revealed that 3-(phenylsulfonyl)thieno[2,3-e][1,2,3]triazolo[1,5-a]pyrimidines are highly selective 5-HT6 receptor ligands.

(3-Phenylsulfonylcycloalkano[e and d]pyrazolo[1,5-a]pyrimidin-2-yl)amines: potent and selective antagonists of the serotonin 5-HT6 receptor.

5-HT(6) receptors are exclusively localized in the CNS and have high affinity with many psychotropic agents. Though the role of this receptor in many CNS diseases is widely anticipated, lack of definite progress in the development of 5-HT(6) receptor-oriented drugs indicates a need for further discoveries of novel chemotypes with high potency and high selectivity to the receptor. Here we present preparations and biological evaluation of a series of (3-phenylsulfonylcycloalkano[e and d]pyrazolo[1,5-a]pyrimidin-2-yl)amines. Phenylsulfonylcyclopentapyrazolopyrimidine 7 was found to be a highly selective 5-HT(6) receptor antagonist with high affinity (low picomolar range) and potency. 7 and a few of its analogues were further tested for biological effect on 5-HT(2B) receptors and hERG potassium channels, potential liability targets. Such liability appears to be minimal, based on the in vitro data.

Solution phase parallel synthesis of substituted 3-phenylsulfonyl-[1,2,3]triazolo[1,5-a]quinazolines: selective serotonin 5-HT(6) receptor antagonists.

Here we present the solution phase parallel synthesis of a combinatorial library consisting of 776 new substituted 3-phenylsulfonyl-[1,2,3]triazolo[1,5-a]quinazolines and a study of the relation of their structure with a 5-HT(6) receptor antagonistic activity in a functional cell (HEK 293) analysis and radioligand competitive binding. We have found highly active and selective 5-HT(6)R antagonists. The most active 5-HT(6)R antagonists have IC(50) <100 nM in a functional assay, and K(i) <10 nM in a binding assay, which is 100 times higher than the activity with respect to other serotonin receptors.

Synthesis of cycloalkane-annelated 3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines and their evaluation as 5-HT6 receptor antagonists.

Synthesis and biological evaluation of 1 ('angular') and 2 ('linear') cycloalkane-annelated 3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines as novel ligands of the 5-HT(6) receptors are disclosed. The new compounds 1 and 2 are highly selective antagonists of the receptor with sub-nanomolar affinities (K(i)<1 nM). In its structure, this new chemotype lacks a basic ionizable side chain, which is considered as the characteristic feature of the 5-HT(6) receptor antagonists pharmacophore model.

8-Sulfonyl-substituted tetrahydro-1H-pyrido[4,3-b]indoles as 5-HT6 receptor antagonists.

A series of novel 8-sulfonyl-substituted 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indoles (THPI) has been synthesized and their ability to interact with 5-HT(6) receptors evaluated in cell-based and radioligand binding assays. Amongst evaluated THPIs, compounds 9.HCl and 20.HCl have been identified as the most potent 5-HT(6) receptor antagonists with K(i) values equal to 2.1 nM and 5.7 nM and IC(50) values (functional assay) equal to 15 nM and 78 nM, respectively. Affinities of these two compounds for several serotonin receptors in the competitive radioligand binding assays as well as their specificity profiles against a panel of therapeutic targets have been determined.

Synthesis and biological activity of 5-styryl and 5-phenethyl-substituted 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indoles.

Syntheses, biological evaluation, and structure-activity relationships for a series of novel 5-styryl and 5-phenethyl analogs of dimebolin are disclosed. The novel derivatives and dimebolin share a broad spectrum of activities against therapeutically relevant targets. Among all synthesized derivatives, 2,8-dimethyl-5-[(Z)-2-phenylvinyl]-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole and its 5-phenethyl analog are the most potent blockers of 5-HT(7), 5-HT(6), 5-HT(2C), Adrenergic alpha(2) and H(1) receptors. The general affinity rank order towards the studied receptors was Z-3(2)>4(2)4(3)>>dimebolin, all of them having highest affinities to 5-HT(7) receptors.

Synthesis and biological evaluation of novel gamma-carboline analogues of Dimebon as potent 5-HT6 receptor antagonists.

Synthesis, biological evaluation and structure-activity relationships for a series of novel gamma-carboline analogues of Dimebon are described. Among the studied compounds, gamma-carbolines 3{8} and 3{14} have been identified as potent small molecule antagonists of histamine H(1) (IC(50)=0.1 microM) and serotonin 5-HT(6) (IC(50)=0.37 microM) receptors, respectively.

Synthesis and caspase-3 inhibitory activity of 8-sulfonyl-1,3-dioxo-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines.

A convenient synthesis of novel 8-sulfonyl-1,3-dioxo-4-methyl-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines is described. As key steps to assemble the target molecular scaffold, our method features (a) Pfitzinger reaction of isatin-5-sulfonate 1 with methyl 3-oxo-3-phenylpropanoate, (b) formation of 1-(1H-pyrazol-4-yl)-1H-pyrrole-2,5-dione intermediate 5, and (c) reaction of sulfinic acid 9 with acrylate or methylacrylate leading to the corresponding sulfonyl propionates. Two compounds, ester 11 and morpholide 13, have been identified as potent inhibitors of caspase-3 with IC50 = 6 nM. Our primary data suggest noncompetitive and reversible character of caspase-3 inhibition.

Pyrrolo[3,4-c]quinoline-1,3-diones as potent caspase-3 inhibitors. Synthesis and SAR of 2-substituted 4-methyl-8-(morpholine-4-sulfonyl)-pyrrolo[3,4-c]quinoline-1,3-diones.

Synthesis, biological evaluation and structure-activity relationships for a series of 2-substituted 4-methyl-8-(morpholine-4-sulfonyl)-1,3-dioxo-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines are described. These compounds represent a new chemotype of nonpeptide small molecule inhibitors of caspase-3. Among the studied compounds, several potent inhibitors with IC50 in the range of 3-10 nM have been identified. The most active compound within this series, 7{49} and 7{58}, inhibited caspase-3 with IC50=3 nM.

Synthesis and structure-activity relationship of 4-substituted 2-(2-acetyloxyethyl)-8-(morpholine-4-sulfonyl)pyrrolo[3,4-c]quinoline-1,3-diones as potent caspase-3 inhibitors.

Synthesis, biological evaluation, and SAR dependencies for a series of novel 1,3-dioxo-2,3-dihydro-1H-pyrrolo[3,4-c]quinoline inhibitors of caspase-3 are described. The inhibitory activity of the synthesized compounds is highly dependent on the nature of 4-substituents on the core scaffold. 4-methyl-and 4-phenyl-substituted derivatives, which were the most active compounds within this series, inhibited caspase-3 with IC50 of 23 and 27 nM, respectively.

1,3-Dioxo-4-methyl-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines as potent caspase-3 inhibitors.

Synthesis, biological evaluation and structure-activity relationships for a series of novel nonpeptide small molecule inhibitors of caspase-3 are described. Among the studied compounds, 8-sulfamide derivatives of 1,3-dioxo-4-methyl-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines have been identified as potent inhibitors of caspases-3. The most active compound within this series (8f) inhibited caspase-3 with IC(50)=4 nM.