Synthesis and pharmacological evaluation of novel fused thiophene derivatives as 5-HT2A receptor antagonists: Molecular modeling study

Novel derivatives of cyclopentathienopyrimidinediones 6, pyridothienopyrimidinediones 7, ethyl cycloheptathiophene-3-carboxylates 10, ethyl tetrahydrothienopyridine-3-carboxylates 11, tetrahydrocycloheptathienopyrimidin-4(3H)-ones 12, tetrahydrotriazolobenzothienopyrimidin-5(4H)-ones 17 and tetrahydro-5H-cycloheptathienopyrimidin-4(3H)-ones 21 have been synthesized and tested for their 5-HT2A antagonist activity. Preliminary pharmacological studies showed that compounds 3-[2-[4-phenylpiperazin-1-yl]ethyl]-6,7-dihydro-5H-cyclopenta[b]thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione 6a and ethyl 2-[[4-(2-methoxyphenyl)piperazin-1-yl]acetylamino]-4,5,6,7-tetrahydro-6-methylthieno[2,3-c]pyridine-3-carboxylate 11d were found to be the most active molecules as 5-HT2A antagonists. Molecular modeling and pharmacophore prediction methodology are used to study the structural features required for 5-HT2A antagonist properties of the active compounds compared with nonactive species by means of the molecular mechanic method. The 2-methoxy substituent in the structure of 11d seems to be necessary for its full antagonistic properties. Optimal placement of basic nitrogen relative to the plane of thiophene core was found to have a profound effect on affinity and biological activity.

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