Convergent synthesis of an elusive hexasaccharide corresponding to the cell-wall polysaccharide of the β-hemolytic Streptococcus Group A

Abstract A convergent synthesis of a hexasaccharide corresponding to the cell-wall polysaccharide of the β-hemolytic Streptococcus Group A is described. The strategy relies on the preparation of a key linear trisaccharide unit β- d -Glc p Nac-(1 → 3)-α- l -Rha p (1 → 2)-α- l -Rha p which has previously resisted our efforts. The trisaccharide functions both as a glycosyl acceptor and donor to give an elusive hexaccharide. This fully functionalized unit can serve, in turn, as a glycosyl acceptor or donor for the synthesis of higher-order structures. Deprotection gives a hitherto unknown hexasaccharide for use as a hapten in immunochemical studies. The characterization of all compounds by high-resolution 1 H and 13 C NMR spectroscopy is also described.