Novel 2-substituted cocaine analogs: binding properties at dopamine transport sites in rat striatum

A novel scheme utilizing vinylcarbenoid precursors has been developed for the synthesis of novel tropane analogs of cocaine. Using this method, 15 analogs were prepared and tested for activity in binding to dopamine transporters in rat striatal membranes using [125I]RTI-55. In all the analogs, the aryl group at the 3 position was directly bound to the tropane ring (as in WIN 35,428), and methyl or ethyl ketone moieties were present at the 2 position instead of the typical ester group. The most potent analog was a 2-naphthyl derivative (IC50 value of 0.2 nM, vs. 170 nM for cocaine), while replacement of the aryl with either ethyl or cyclohexyl drastically reduced potency (to > 50 microM and 5 microM, respectively).