Design, synthesis and binding properties of novel and selective 5-HT3 and 5-HT4 receptor ligands

This work reports the synthesis and the binding tests on the 5-HT3 and 5-HT4 receptors of new thienopyrimidopiperazine and piperazinylacylaminodimethylthiophene derivatives, in order to identify potent and selective ligands for each receptor. The compound with higher affinity and selectivity for the 5-HT3 over the 5-HT4 receptor was the 3-amino-2-(4-benzyl-1-piperazinyl)-5,6-dimethyl-thieno[2.3-d]pyrimidin-4(3H)-one 28 (5-HT3 K-i = 3.92 nM, 5-HT4 not active), the compound with higher affinity and selectivity for the 5-HT4 over the 5-HT3 receptor was the 2-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butanoylamino]-4,5-dimethyl-3-thio-phenecarboxylic acid ethyl ester 41 (5-HT4, K-i=81.3 nM. 5-HT3 not active). Conformational analyses were carried out on the compounds of the piperazinylacylaminodimethylthiophene series (39-42) taking compound 41 as the template. (C) 2000 Editions scientifiques et medicales Elsevier SAS.