Synthesis of Glycan Chains of Glycoproteins

Recent aspects of synthetic studies on oligosaccharides of N-glycoproteins are described in three parts ; (1) synthesis of core structure, (2) synthesis of variable region, (3) coupling between core structure and variable region. Synthesis of core structure, the trisaccharides containing one β-D-mannopyranosyl residue and two 2-acetamide-2-deoxy-β-D-glucopyranosyl residues, was designed by employing a protected chitobiosyl derivative and a di-O-allyl-di-O-benzyl-mannopyranosyl donor The β-mannopyranosylations were achieved by use of Paulsen's promotor. Synthesis strategies for variable region of both high-mannose type and complex type were developed mainly by taking advantage of new regioselective protective procedures. Coupling between the core structure and variable regions were successfully achieved by use of oligosaccharide halides as well as trichloroacetoimidates as the glycosyl donors.