Synthesis of a Set of Staphylococcus Aureus Capsular Polysaccharide Type 1 Oligosaccharides Carrying Taurine Esters

Staphylococcus aureus is a Gram-positive bacterium that is responsible for severe nosocomial infections. The protective capsular polysaccharides (CPs), which are key elements of the cell wall, have been proposed as promising candidate antigens. Several CP types have been identified including CP1, CP5, and CP8, and serotype 1 has been associated with increased resistance to phagocytosis and virulence. Here, the synthesis of a set of S. aureus CP 1 (strain M and D) trisaccharides, composed of an α-N-acetyl d-fucosamine and two α-N-acetyl d-galactosaminuronic acid residues, carrying taurine esters together with a nontaurinated hexasaccharide, is reported. To be able to tune the taurine substitution pattern, an orthogonal C-6-OH protecting group strategy for the galactosamine building blocks was developed, in conjunction with a postglycosylation oxidation protocol to site selectively introduce the taurine amide substitutions. The stereoselectivity in the glycosylations was secured using a silylene-protected 2-azido galactose synthon.