The impact of spacer structure on 5-HT7 and 5-HT1A receptor affinity in the group of long-chain arylpiperazine ligands

New cis-, trans-2-butene and 1,2-bismethylbenzene analogues of MM77 and NAN-190 (1-{4-[4-(2-methoxyphenyl)-piperazin-1-yl]-butyl}-pyrrolidine-2,5-dione and isoindole-1,3-dione, respectively) were synthesized. The differences in their in vitro affinity for serotonin 5-HT7 and 5-HT1A receptors were explained using a conformational analysis. A bioactive conformation of those compounds for the 5-HT7 receptor, different from that established for 5-HT1A, was proposed.