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

Two trisaccharides, α-d-Galp-(1→3)-β-d-ManpNAc-(1→4)-β-d-Glcp and α-d-Glcp-(1→3)-β-d-ManpNAc-(1→4)-β-d-Glcp, 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 CH2Cl2 for β-linkages) and DMTST (in Et2O 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.