Novel autoxidation and Michael addition of a butenolide-containing sugar leading to a C-branched-chain glucopyranosidulose, and X-ray structure of intermediates.

A butenolide-containing sugar available from the aldol condensation of methyl 4,6-O-benzylidene-alpha-D-glucopyranosid-2-ulose with diethyl malonate is autoxidized at the C-3 position into the corresponding alpha,beta-unsaturated gamma-lactone sugar by air, which subsequently undergoes 1,4-conjugate (Michael) addition of hydroxide ion (or water) leading to a C-branched-chain glucopyranosidulose. The autoxidations are also performed in weakly basic, neutral and weakly acidic medium, respectively.