It is now accepted that (-)-cocaine binds to specific recognition sites associated with monoamine transporters in the mammalian brain. In this study, several analogs of 3 beta-phenyltropane-2 beta-carboxylic acid methyl ester were prepared and their potency for inhibiting the binding of [3H]-3 beta-(4-fluorophenyl)tropane-2 beta-carboxylic acid methyl ester to primate caudate-putamen was evaluated. The synthesis and binding affinity of 3 beta-(3,4- dichlorophenyl)tropane-2 beta-carboxylic acid methyl ester, one of the most potent cocaine congeners yet reported, is presented. The feasibility of synthesizing high-affinity ligands for cocaine recognition sites and their suitability as PET imaging ligands for cocaine receptors in vivo is demonstrated.

Cocaine is a stimulant drug with a high abuse liability. Although it inhibits several monamine transporters in the mammalian brain, its primary mechanism of action has been ascribed to its inhibition of the dopamine transporter. The synthesis, characterization, and receptor binding properties of all eight isomers of a unique tropane analog, 2-carbomethoxy-3-[bis(4-fluorophenyl)-methoxy]tropane is described. In addition, we report that the S-enantiomer, (S)-(+)-2 beta- carbomethoxy-3 alpha-[bis(4-fluorophenyl)methoxy]tropane, Difluoropine, is a potent (IC50 10.9 nM) and selective (324 [DA/5HT]) ligand for the dopamine transporter.

Cocaine is a potent stimulant of the mammalian central nervous system. Its reinforcing and stimulant properties have been associated with its propensity to bind to monoamine transporter systems. It has generally been assumed that the amino function on monoamines is a requirement for binding to monoamine transporters. In particular, the 8-amino function on the tropane skeleton of cocaine and cocaine analogs has been assumed to provide an ionic bond to the aspartic acid residue on the dopamine transporter (DAT). We have prepared the first 8-oxa analogs of the 3-aryltropanes (WIN compounds) and have found that the 3 beta-(3,4-dichlorophenyl) (6g) and 3 alpha-(3,4-dichlorophenyl) (7g) analogs are particularly potent (IC50 = 3.27 and 2.34 nM, respectively) inhibitors of the dopamine transporter. We now describe the synthesis and biology of the family of 2-carbomethoxy-3-aryl-8-oxabicyclo[3.2.1]octanes and demonstrate that an amino nitrogen is not required for binding to the DAT.