Synthesis of Oligosaccharides Resembling the Serotype 18 Capsular Polysaccharide as a Basis for Glycoconjugate Vaccine Development.

Here we report the first total synthesis of several oligosaccharides resembling the capsular polysaccharide of swine pathogen serotype 18 repeating unit [→3)-d-GalNAc(α1-3)[d-Glc(β1-2)]-d-GalA4OAc(β1-3)-d-GalNAc(α1-3)-d-BacNAc4NAc(α1→]. Access to the pentasaccharide repeating unit antigen proved to be very challenging due to the poor reactivity in the context of the trisaccharide. The challenge was overcome by the creation of a galacturonic acid in a late stage of the synthesis.