Stereospecific synthesis of α-C-glycosyl derivatives ("α-C-glycosides") of N-acetylneuraminic acid by samarium-mediated reductive desulfonylation of a glycosyl phenylsulfone

A samarium-mediated Barbier reaction was performed to afford N-acetylneuraminic acid alpha-C-glycosyl compounds ("alpha-C-glycosides") in excellent yield. The neuraminic acid phenyl sulfone or 2-pyridyl sulfone derivatives reacted with ketones or aldehydes resulting in the instantaneous and stereospecific formation of Neu5Ac alpha-C-glycosides. The phenyl and the 2-pyridyl sulfone derivatives were equally effective in this reaction. Finally, this procedure was successfully applied to the preparation of C-disaccharide, alpha-Neu5Ac-(2-->6) Gal. (C) 1998 Elsevier Science Ltd. All rights reserved.