Chemo-enzymatic synthesis of tetra-, penta-, and hexasaccharide fragments of the capsular polysaccharide of Streptococcus pneumoniae type 14 Original Research Article

The chemo-enzymatic synthesis is described of β-d-Glcp-(1→6)-[β-d-Galp-(1→4)]-β-d-GlcpNAc-(1→3)-β-d-Galp-(1→O(CH2)6NH2 (1), β-d-Glcp-(1→6)-[β-d-Galp-(1→4)]-β-d-GlcpNAc-(1→3)-β-d-Galp-(1→4)-β-d-Glcp-(1→O(CH2)6NH2 (2), β-d-Galp-(1→4)-β-d-GlcpNAc-(1→3)-β-d-Galp-(1→4)-β-d-Glcp-(1→O(CH2)6NH2 (3), and 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 (4), representing fragments of the repeating unit of the Streptococcus pneumoniae serotype 14 capsular polysaccharide. Linear intermediate oligosaccharides 5–8 were synthesized via chemical synthesis, followed by enzymatic galactosylation using bovine milk β-1,4-galactosyltransferase as a catalyst. The title oligosaccharides form suitable compounds for conjugation with carrier proteins, to be tested as potential vaccines in animal models.