Chemo-enzymatic synthesis of a tetra- and octasaccharide fragment of the capsular polysaccharide of Streptococcus pneumoniae type 14 Original Research Article

The chemo-enzymatic synthesis is described of tetrasaccharide β-d-Galp-(1→4)-β-d-Glcp-(1→6)-[β-d-Galp-(1→4)]-β-d-GlcpNAc-(1→O(CH2)6NH2 (1) and octasaccharide β-d-Galp-(1→4)-β-d-Glcp-(1→6)-[β-d-Galp-(1→4)]-β-d-GlcpNAc-(1→3)-β-d-Galp-(1→4)-β-d-Glcp-(1→6)-[β-d-Galp-(1→4)]-β-d-GlcpNAc-(1→O(CH2)6NH2 (2), representing one and two tetrasaccharide repeating units of Streptococcus pneumoniae serotype 14 capsular polysaccharide. In a chemical approach, the intermediate linear trisaccharide 3 and hexasaccharide 4 were synthesized. Galactose residues were β-(1→4)-connected to the internal N-acetyl-β-d-glucosamine residues by using bovine milk β-1,4-galactosyltransferase. Both title oligosaccharides will be conjugated to carrier proteins to be tested as potential vaccines in animal models.