Stereospecific uncatalyzed α-O-glycosylation and α-C-glycosidation by means of a new D-gulal-derived α vinyl oxirane

The reaction of alpha vinyl oxirane 5, prepared through a new route to the D-gulal system, with O-nucleophiles (alcohols and di-O-isopropylidene-alpha-D-monosaccharides) and C-nucleophiles (lithium alkyls) affords, in a completely stereoselective way, the corresponding 2-unsaturated alpha O- and C-glycosides having the same configuration as the starting epoxide.