Stereoselective synthesis of 2,2-bis(C-branched-chain)glucopyranosid-3-ulose via an autoxidation–Michael addition reaction

2,2-Bis(C-branched-chain)glucopyranosid-3-uloses, designed for the preparation of biologically active natural product iridoid derivatives, are synthesized selectively by the new reaction of butenolide-containing sugar with active methylene compounds, and the new reaction is clarified as autoxidation followed by Michael addition of carbanion.