Chemoenzymatic Synthesis of Ramosetron Hydrochloride

A new method for the synthesis of ramosetron hydrochloride,the most wildly used 5-HT3 receptor antagonist,was reported.The intermediate 8 was obtained in a high e.e.value via lipase catalyzed hydrolytic kinetic resolution.Then enantiomerically pure ramosetron hydrochloride was synthesized in two steps with excellent yield (the total yield is 24.6％).The method provides a new environment friendly and atom economy way to synthesize enantiomerically pure ramosetron.