S-benzoxazolyl (SBox) glycosides in oligosaccharide synthesis:: Novel glycosylation approach to the synthesis of β-D-glucosides, β-D-galactosides, and α-D-mannosides

Per-acetylated and per-benzoylated S-benzoxazolyl (SBox) glycosides have been synthesized and applied to highly efficient 1,2-trans glycosylation. Complete stereoselectivities and remarkably high yields were achieved for the synthesis of beta-D-glucosides, beta-D-galactosides, and alpha-D-mannosides. It was also demonstrated that benzoylated 'disarmed' SBox glycosides could be selectively activated in the presence of both armed and disarmed ethyl thioglycosides. Convergent synthesis of the tetrasaccharide beta-D-Glc-(1-6)-beta-D-Gal-(1-6)-beta-D-GlcNAc-(1-6)-alpha-D-GlcOMe was achieved in three sequential selective glycosylation steps.