Synthesis of tetra- and pentasaccharides corresponding to the capsular polysaccharide of Streptococcus pneumoniae type 9A&L, 9N and 9A Original Research Article

Two tetrasaccharides, α-d-GlcAp-(1→3)-α-d-Galp-(1→3)-β-d-ManpNAc-(1→4)-β-d-Glcp and α-d-GlcAp-(1→3)-α-d-Glcp-(1→3)-β-d-ManpNAc-(1→4)-β-d-Glcp (protected form), and a pentasaccharide, α-d-Glcp-(1→4)-α-d-GlcAp-(1→3)-α-d-Galp-(1→3)-β-d-ManpNAc-(1→4)-β-d-Glcp have been synthesised from 2-aminoethyl glycoside trisaccharide acceptors in a linear approach via consecutive α-glycosylations. Ethyl thioglycosides were used as glycosyl donors and DMTST in Et2O or NIS/TfOH in CH2Cl2 were employed as promoters.