New potent 5-HT2A receptor ligands containing an N′-cyanopicolinamidine nucleus: Synthesis and in vitro pharmacological evaluation

Abstract N′-cyanopicolinamidine derivatives, linked to an arylpiperazine moiety, were prepared and their affinity to serotonin 5-HT 1A , 5-HT 2A and 5-HT 2C receptors were evaluated. The combination of structural elements (heterocyclic nucleus, alkyl chain and 4-substituted piperazine) known to be critical for affinity to 5-HT 1A receptors and the proper selection of substituents led to compounds with high specificity and affinity towards serotoninergic receptors. In binding studies, several molecules showed affinity in nanomolar and subnanomolar range at 5-HT 2A and moderate to no affinity for other relevant receptors (5-HT 1A , 5-HT 2C , D 1 , D 2 , α 1 and α 2 ). N′-cyano-N-(3-(4-(3-chlorophenyl)piperazin-1-yl)propyl)-picolinamidine ( 4l ) with K i  = 0.000185 nM, was the most active and selective derivative for the 5-HT 2A receptor compared to other serotoninergic, dopaminergic and adrenergic receptors.