A Convenient Entry to C2- and C3-Substituted Gulono-gamma-lactone Derivatives from L-Ascorbic Acid

摘要

A convenient method to obtain unknown chiral C2- and C3-functionalized aldono-l,4-lactone derivatives starting from L-ascorbic acid,which would be valuable in the synthesis of derivatives of various pharmacologically active agents for structure-activity studies,is described.The practicality of this approach is demonstrated by the synthesis of a series of 5,6-O-isopropylidene-2-allyl-3-keto-L-galactono-gamma-lactone and 5,6-O-isopropylidene-3-allyl-2-keto-L-galactono-gamma-lactone derivatives using the thermal Claisen rearrangement of the corresponding 3-O- and 2-O-allyl derivatives of 5,6-O-isopropylidene-L-ascorbic acid,respectively,followed by stereospecific reduction to the corresponding alcohols.The synthetic steps are shown to be efficient,and enantiospecific,and they proceed with high yields.