Development of 3-phenyltropane analogues with high affinity for the dopamine and serotonin transporters and low affinity for the norepinephrine transporter.

Previous studies showed that the mixed monoamine transporter inhibitor (6, RTI-112) reduced cocaine self-administration at a high level of serotonin transporter (5-HTT) occupancy with no detectable dopamine transporter (DAT) occupancy. In this study, a series of 3beta-(substituted phenyl)tropane-2beta-carboxylic acid methyl esters (7a-g), 3beta-(4-methoxyphenyl)tropane-2beta-carboxylic acid esters (8a-j), and 3beta-(4-methoxyphenyl)-2beta-[3-(4'-methylphenyl)isoxazol-5-yl]tropane (9) were synthesized and evaluated for their monoamine transporter binding affinities to identify potent and selective compounds for both the DAT and 5-HTT relative to the norepinephrine transporter (NET). A number of compounds showed high binding affinities for both the DAT and 5-HTT and low affinity for the NET. 3Beta-(4-methoxyphenyl)tropane-2beta-carboxylic acid 2-(3-iodo-4-aminophenyl)ethyl ester (8i) with an IC(50) value of 2.5 nM for the DAT and K(i) values of 3.5 and 2040 nM for the 5-HTT and NET, respectively, is the most potent and selective compound for the DAT and 5-HTT relative to the NET in this study.