Structural studies of the O-specific polysaccharide of Vibrio cholerae O8 using solvolysis with triflic acid Original Research Article

The O-specific polysaccharide (OPS) of Vibrio cholerae O8 was isolated by mild acid degradation of the lipopolysaccharide and studied by two-dimensional NMR spectroscopy, including NOESY and heteronuclear multiple-bond correlation (HMBC) experiments. The OPS was found to have a tetrasaccharide repeating unit with the following structure:→4)-β-d-GlcpNAc3NAcylAN-(1→4)-β-d-ManpNAc3NAcAN-(1→4)-α-l-GulpNAc3NAcA-(1→3)-β-d-QuipNAc4NAc-(1→where QuiNAc4NAc is 2,4-diacetamido-2,4,6-trideoxyglucose, GlcNAc3NAcylAN is 2-acetamido-3-(N-formyl-l-alanyl)amino-2,3-dideoxyglucuronamide, ManNAc3NAcAN is 2,3-diacetamido-2,3-dideoxymannuronamide, and GulNAc3NAcA is 2,3-diacetamido-2,3-dideoxyguluronic acid. The OPS was stable towards acid hydrolysis and solvolysis with anhydrous hydrogen fluoride, but could be cleaved selectively with trifluoromethanesulfonic (triflic) acid by the glycosidic linkages of β-QuiNAc4NAc and α-GulNAc3NAcA. The structures of the oligosaccharides obtained that were elucidated by electrospray ionization (ESI) MS and NMR spectroscopy, confirmed the OPS structure.