Synthesis and pharmacology of 6-substituted benztropines: discovery of novel dopamine uptake inhibitors possessing low binding affinity to the dopamine transporter

A series of 6α- and 6β-substituted benztropines were synthesized. A marked enantioselectivity was observed for the 6β-methoxylated benztropines, the (1R)-isomers being more potent than the corresponding (1S) compounds. The racemic 6α-methoxy-3-(4′,4″- difluorodiphenylmethoxy)-tropane (5g) was the most potent compound. It has been found that modifications at the 6-position of benztropine might reduce the DAT binding affinity, maintaining otherwise a significant dopamine uptake inhibitory activity. A reinvestigation of the absolute configuration of 6β-methoxytropinone proved the 6R configuration for the (+)-enantiomer.