Metal-catalyzed Stereoselective and Protecting-group-free Synthesis of 1,2-cis-Glycosides Using 4,6-Dimethoxy-1,3,5-triazin-2-yl Glycosides as Glycosyl Donors

4,6-Dimethoxy-1,3,5-triazin-2-yl glycosides, glycosyl donors prepared in one step from free saccharides without protection of the hydroxy groups, were stereoselectively and equivalently converted to the corresponding 1,2-cis-glycosides by using a catalytic amount of metal catalyst. This reaction was successfully applied not only to monosaccharides, but also to di- and oligosaccharides.