ZnI-Mediated -Glycosylations of Various Constrained Glycosyl Donors: Recent Advances in -Selective Glycosylations.

An efficient and versatile glycosylation methodology is crucial for the systematic synthesis of oligosaccharides and glycoconjugates. A direct intermolecular and an indirect intramolecular methodology have been developed, and the former can be applied to the synthesis of medium-to-long-chain glycans like that of nucleotides and peptides. The development of a generally applicable approach for the stereoselective construction of glycosidic bonds remains a major challenge, especially for the synthesis of 1,2- glycosides such as β-mannosides, β-L-rhamnosides, and β-D-arabinofuranosides with equatorial glycosidic bonds as well as α-D-glucosides with axial ones. This review introduces the direct formation of -glycosides using ZnI-mediated -glycosylations of various constrained glycosyl donors, as well as the recent advances in the development of stereoselective -glycosylations.