Synthesis of both enantiomers of baclofen using ( R)- and ( S)- N-phenylpantolactam as chiral auxiliaries

Abstract

Esterification of racemic 4-nitro-3-(4-chlorophenyl)butanoic acid with ( R)- or ( S)- N-phenylpantolactam as the chiral auxiliary allowed us to obtain the (3 R,3′ R)- or (3 S,3′ S)-nitro esters with >98:2 dr after column chromatography. Hydrolysis of the resulting diastereopure nitro esters gave the corresponding enantiopure nitro acids, which were readily converted in high yields into either ( R)- or ( S)-baclofen hydrochloride.