Synthesis and structure-activity relationships of 1-aralkyl-4- benzylpiperidine and 1-aralkyl-4-benzylpiperazine derivatives as potent σ ligands

In the attempt to define more accurately structure-affinity relationships for ó1 and ó2 ligands,we synthesized and tested on ó subtype receptors a series of aralkyl derivatives of 4-benzylpiperidine,in which the effect of modifications on the aralkyl moiety was studied in a systematicway. The affinity of the compounds here described varied to a great extent, with a ó2/ó1selectivity ranging from 0.1 to 9. Thus, to confirm the ability of the piperazine derivative tobind to ó1 receptors in a different way than piperidines, we synthesized and tested a series ofpiperazine compounds; the comparison of their affinity with that of the correspondingpiperidines strongly supports the possibility of a different binding mode. While the compoundshere described are on the whole selective for ó vs serotonin 5-HT1A and dopamine D2 receptors,9aa, 9ba and 9ab possess a remarkable affinity for both ó and 5-HT1A receptors, with Ki inthe nanomolar range, and are selective with respect to D2 receptors. They displayed also apartial agonist profile in a human 5-HT1A [35S]GTPçS binding assay, suggesting their potentialuse as atypical antipsychotic agents.