Synthesis of oligosaccharides corresponding to Streptococcus pneumoniae type 9 capsular polysaccharide structures

Abstract

Two trisaccharides, α- d-Gal p-(1→3)-β- d-Man pNAc-(1→4)-β- d-Glc p and α- d-Glc p-(1→3)-β- d-Man pNAc-(1→4)-β- d-Glc p, corresponding to structures from Streptococcus pneumoniae capsular polysaccharides type 9A, L, V and type 9N, respectively, have been synthesised as 2-aminoethyl glycosides and as protected TMSE glycosides. Ethyl thioglycosides were used as glycosyl donors and NIS/TfOH (in CH 2Cl 2 for β-linkages) and DMTST (in Et 2O for α-linkages) as promoters in the glycosylations. The β-ManNAc motif was introduced at the disaccharide level by azide displacement of a 2- O-triflate with β- d- gluco configuration. The protecting group patterns allow continued syntheses of larger structures.