Sugars (saccharides) are useful antigens for the production of vaccines. Examples for this are Vi polysaccharides (ViPS) from Salmolla typhi, which is the cause of typhoid fever in humans. Unfortunately, low yields as well as regio- and stereoselectivity during the chemical synthesis of saccharides hinder the fast development of pertinent vaccines.

Xin-Shan Ye, Peking University, Beijing, China, and colleagues have synthesized di-, tri- and tetrasaccharide ViPS mimics (examples pictured) in good yields and with good stereoselectivities. The team used 2,3-N,O-oxazolidinone-protected glycoside monomers. By adding linker groups at the termini of these oligosaccharides, the researchers were able to extend the size to tetra-, hexa- and octasaccharides using olefin cross metathesis or click chemistry.

The team tested these ViPS mimics in a competitive enzyme-linked immunosorbent assay (ELISA) against ViPS antibodies. The mimics did not outperform ViPS, indicating that further optimization is required to enhance their antigenicity. The results could help other researchers in the future design and synthesis of the oligosaccharide mimics.

• Synthesis and Antigenic Evaluation of Oligosaccharide Mimics of Vi Antigen from Salmonella typhi,
  Gao-Lan Zhang, Lin Yang, Jingjing Zhu, Mengman Wei, Wanjun Yan, De-Cai Xiong, Xin-Shan Ye,
  Chem. Eur. J. 2017, 23, 10670–10677.
  DOI: 10.1002/chem.201702114