Lactonization-mediated glycosylations and their application to oligosaccharide synthesis.

ABSTRACT

The concept of lactonization-mediated and related glycosylations led us to develop new methods of glycosylation such as the 2'-carboxybenzyl (CB) glycoside method, the glycosyl pentenoate/phenylselenyl trifluoromethanesulfonate (PhSeOTf) method, and the glycosyl aryl phthalate method. Highly stereoselective beta-mannopyranosylations were achieved by employing the CB glycoside and the glycosyl pentenoate/PhSeOTf methods. The CB glycoside method was also utilized for stereoselective 2-deoxyglycosylation, beta-arabinofuranosylation, and alpha-galactofuranosylation. In addition, these lactonization-mediated methods of glycosylation were employed for the synthesis of complex oligosaccharides. In particular, the CB glycoside method was successfully applied to the synthesis of repeating oligosaccharide subunits of the O-polysaccharide of the lipopolysaccharide from Danish Helicobacter pylori strains and Escherichia coli 077, the synthesis of oligoarabinofuranosides in mycobacterial cell walls, and the total synthesis of antineoplastic agelagalastatin.