Practical Asymmetric Synthesis of (+)-erythro Mefloquine Hydrochloride

A highly enantioselective and cost efficient process for the synthesis of (+)-erythro mefloquine has been developed. The key step is an enantioselective reduction of pyridyl ketone KI using transfer hydrogenation with formic acid as the hydrogen source. The ratio of formic acid to NEt3 was found to be very important to achieving a highly efficient process.