No abstract

No abstract

No abstract

A series of 6-alkyl-3 beta-benzyl-2-[(methoxycarbonyl)methyl]tropane analogues were synthesized and evaluated as cocaine binding site ligands at the dopamine transporter (DAT). The in vitro affinity (Ki) for the DAT of the 6-alkyl-3 beta-benzyl-2-[(methoxycarbonyl) methyl]tropane analogues was determined by inhibition of [3H]WIN 35,428 in rat caudate putamen tissue. The inhibition of dopamine uptake (IC50) was also measured for selected compounds which demonstrated moderate affinity for the dopamine transporter. The unsubstituted enantiopure analogues (-)-19a (Ki = 33 nM) and surprisingly (+)-20a (Ki = 60 nM) were found to be almost equipotent with the high-affinity binding components of cocaine and WIN 35,065-2 and exhibited slightly more potent dopamine uptake inhibition than both cocaine and WIN 35,065-2. In general, substitution at the 6-position of racemic 19a and 20a with alkyl groups was found to result in decreased activity relative to increased chain length of the substituent. The 3 beta-benzyl-2 beta-[(methoxycarbonyl)methyl]-6 beta-methyltropane (21b; Ki = 57 nM) was the only 6-alkyl derivative to exhibit moderately potent activity. The 6 beta-isomer 21b was 4-fold more potent than the 6 alpha-isomer 19b (Ki = 211 nM) and was nearly equipotent with (-)-19a and (+)-20a as well as with cocaine and WIN 35,065-2. The results of this study further demonstrate the steric constraints associated with the C(6)-C(7) methylene bridge of the tropane ring system for molecular recognition of cocaine analogues at the cocaine binding site(s) on the DAT.

A series of 9-methyl-3 beta-phenyl-2-substituted-9-azabicyclo[3.3.1]nonane derivatives were synthesized and evaluated as cocaine-binding site ligands at the dopamine transporter (DAT). The conformation of the bicyclic structures and the stereochemistry of the substituents were determined by NMR and X-ray crystallography. The in vitro binding affinity (Ki) of the 9-azabicyclo[3.3.1]nonane derivatives was measured in rat caudate-putamen tissue, and they were found to be 100-fold (Ki = 2-14 microM) less potent than cocaine and other tropane analogs. From these results it is evident that the cocaine-binding site at the DAT is very sensitive to structural modifications of the unsubstituted methylene bridge [C(6)-C(7)] of cocaine and cocaine-like compounds.