Palladium-Catalyzed Improved Regio- and Stereoselective O-Glycosylation of D-Glucal-Derived β- and α-Vinyl Oxiranes

A Pd0-catalyzed glycosylation of D-glucal-derived vinyloxiranes as excellent glycosyl donors has been accomplished in a regio- and stereoselective manner. Various glycosyl acceptors upon reaction with vinyl oxiranes 1a and 1b produced the corresponding 2,3-unsaturated O-glycosides in good to excellent yields within five minutes. The above reaction has also been utilized in the synthesis of 2,3-unsaturated trisaccharides, which are potential precursors of fully oxygenated, deoxy and dideoxy sugars.