ENANTIOSELECTIVE SYNTHESIS OF FULLY PROTECTED ANTI 3-AMINO-2-HYDROXY BUTYRATES

An efficient enantioselective synthesis of fully protected anti 3-amin o-2hydroxybutyrates has been developed. Starting from enantiomerically enriched anti N-diphenylmethyl-3-amino-1,2-butanediol, after a change in the nitrogen protecting group, the primary alcohol was protected b y regioselective reduction of the corresponding p-methoxybenzylidene a cetal. Formation of the oxazolidine and deprotection of the primary al cohol followed by oxidation afforded protected alpha-hydroxy-beta-amin o acids in good yield. Since the source of asymmetry is a catalytic Sh arpless epoxidation, both enantiomeric series are available and the me thodology developed here is expected to be of broad applicability.