Synthesis of the Vibrio cholerae O1 Ogawa and Inaba terminal disaccharides with dioxolane-type spacers and their coupling to proteins

The disaccharide, which corresponds to the terminal fragment of the Vibrio cholerae O1 LPS, was prepared starting from the corresponding trichloroacetimidate derivative of the monosaccharide in the presence of trimethylsilyl triflate. After selective reduction of the azido group, the reaction with 2,4-di-O-acetyl-3-deoxy-L-glycero-tetronic acid in the presence of EEDQ afforded the corresponding amides. The cleavage of dioxolane protecting group followed by careful deacetylation and coupling with Bovine Serum Albumin or Meningococcal Outer Membrane Protein in the presence of sodium cyanoborohydride gave the corresponding neoglycoconjugates.