A novel approach to the stereocontrolled synthesis of C-vinyl beta-D-galactopyranosides.

Reaction of a lithiated dithiinyl reagent with a O-perbenzylated D-glycono-delta-lactone readily generates the corresponding masked C-vinyl galactosides in high yields and full beta-selectivity. Removal of the sulfur mask renders the free vinyl aglycone with the vinyl group in either the Z or E configuration, depending on the desulfurization conditions chosen.