Syntheses of 3-carbomethoxy-4-(aryl)piperidines and in vitro and in vivo pharmacological evaluation: Identification of inhibitors of the human dopamine transporter

A series of 3-carbomethoxy-4-(aryl-substituted)piperidines with various aryl groups were synthesized and examined for binding and reuptake inhibition at the human dopamine transporter, the human serotonin transporter, and the human norepinephrine transporter. The binding potency and reuptake inhibition efficacy was compared with that of (-)-cocaine to determine the significance of removing the two-carbon bridge of the cocaine nucleus on the inhibition of transporter binding and reuptake. Of the transporters examined, the substituted piperidines were relatively selective for the human dopamine transporter. In all cases examined, the cis-diastereomer of the 3-carbomethoxy-4-(aryl-substituted)piperidine was observed to be a more potent inhibitor of the human dopamine transporter than the trans diastereomer. Based on the K_i (binding) and IC₅₀ (reuptake inhibition) values obtained, the most potent inhibitor of the series was cis-3-carbomethoxy-4-(4′-chlorophenyl)piperidine, and this compound suppressed spontaneous- and cocaine-induced stimulation in non-habituated male Swiss-Webster mice. The conclusion is that substantial portions of the cocaine structure can be dissected away to provide compounds with significant binding and reuptake inhibition of the human dopamine transporter.