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

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)-beta -D-GlcpNAc3NAcylAN-(1 --> 4)-beta -D-ManpNAc3NAcAN-(1 --> 4)-alpha- L-GulpNAc3NAcA-(1 --> 3) -beta -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 beta -QuiNAc4NAc and alpha -GulNAc3NAcA. The structures of the oligosaccharides obtained that were elucidated by electrospray ionization (ESI) MS and NMR spectroscopy, confirmed the OPS structure. (C) 2001 Elsevier Science Ltd. All rights reserved.