Antagonists of 5-HT₆ receptors. Substituted 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[3,4-e]pyrimidines and 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[4,3-d]pyrimidines-Synthesis and 'structure-activity' relationship.

Synthesis and biological evaluation of a new series of structurally unrestricted and intramolecular hydrogen bond restricted derivatives of 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[3,4-e]pyrimidines (angular tricyclics) and 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[4,3-d]pyrimidines (linear tricyclics) are described. Structurally restricted derivatives are highly potent and selective blockers of 5-HT(6) receptors with little difference between angular or linear shape of the tricyclic core, the angular species being only slightly more potent. The angular representative of 3-(phenylsulfonyl)pyrazolo[1,5-a]pyrido[3,4-e]pyrimidines, 5, can be considered as more favorable candidate for further development as it shows only weak 5-HT(2B) blocking activity (IC(50)=6.

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.

2-Substituted 5,6-dimethyl-3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines: new series of highly potent and specific serotonin 5-HT6 receptor antagonists.

Syntheses, biological evaluation, and structure-activity relationships for a series of novel 2-substituted 3-benzenesulfonyl-5,6-dimethyl-pyrazolo[1,5-a]pyrimidines are disclosed. In spite of a wide, four orders of magnitude, SAR range (K(i) varied from 260 pM to 2.96 μM), no significant correlation of 5-HT(6)R antagonistic potency was observed with major physiochemical characteristics, such as molecular weight, surface polar area, cLogP, or number of rotatable bonds.

Synthesis and SAR of 3-arylsulfonyl-pyrazolo[1,5-a]pyrimidines as potent serotonin 5-HT6 receptor antagonists.

Syntheses of a series of novel 3-sulfonyl-pyrazolo[1,5-a]pyrimidines and their 5-HT(6) receptor antagonistic structure-activity relationship are disclosed. The nature and position of substituents, which affect their receptor antagonistic activity, are analyzed. Among all synthesized derivatives, {3-(3-chlorophenylsulfonyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-2-yl}-methyl-amine 33 (K(i)=190 pM), (3-phenylsulfonyl-7-methyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methyl-amine 44 (K(i)=240 pM), (3-phenylsulfonyl-5-metoxymethyl-7-methyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methyl-amine 50 (K(i)=270 pM), and (3-phenylsulfonyl-5-methyl-7-metoxymethyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methyl-amine 52 (K(i)=280 pM) are the most potent antagonists of the 5-HT(6) receptors.

(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.

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.

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.