Synthesis, molecular modeling, and biological studies of novel piperidine-based analogues of cocaine: Evidence of unfavorable interactions proximal to the 3α-position of the piperidine ring

A qualitative model for the binding pocket proximal to the 3α-substituent of the piperidine-based monoamine transporter ligands was proposed and tested. Based on this model, a new series of druglike 3α-modified piperidine-based analogues of cocaine were designed, synthesized, and studied for their ability to inhibit reuptake of DA, 5-HT, and NE by the DA, 5-HT, and NE transporters. We found that the insertion of at least one additional methylene group between the piperidine ring and the polar group in the 3α-substituent dramatically improves the activity of the compounds that are generally inactive without this additional linker. Molecular modeling analysis showed that the more flexible 3α-substituents can avoid unfavorable interactions with the binding sites of DAT, SERT, and NET. The present results may have important implications for the elucidation of the structural differences between DA, 5-HT, and NE transporters and for the further design of new leads for development of cocaine abuse medication as well as certain neurological disorders such as ADHD and depression.