title: Syntheses of three interglycosidic isomers of N-acetyl-beta-D-mannosaminyl-L-rhamnoses associated with O-antigens of several gram-negative opportunistic pathogens.
abstract: We achieved practical, highly stereoselective syntheses of three interglycosidic isomers of N-acetyl-beta-D-mannosaminyl-L-rhamnoses, among which a beta(1-->4)-isomer corresponds to the repeating unit of the O-antigen of lipopolysaccharide (LPS) from the opportunistic pathogens Pseudomonas cepacia O5 and Pseudomonas aeruginosa X (Meitert). The other isomers are a beta(1-->2)-disaccharide, a constituent of LPS from Escherichia coli O1A, and an artificial beta(1-->3)-isomer. The disaccharides were obtained by simple three-step reaction sequences from 2-(benzoyloxyimino)-2-deoxyglycosyl halides (mannosamine progenitor). beta-Selective glycosylations of appropriately protected L-rhamnosyl acceptors were performed. Subsequent reduction of the 2-acyloxyimino function to an amino group, N-acetylation, and removal of the protecting groups provided the target disaccharides. 13C-NMR and nuclear Overhauser effect spectra proved to be useful for structural determination of the positional isomers of the disaccharides.
authors.affiliation: School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Kaji
authors.forename: N
authors.initials: N
authors.lastname: Anabuki
authors.forename: S
authors.initials: S
authors.lastname: Zen
mesh_terms: D016905:Gram-Negative Bacterial Infections / Q000276:immunology*; D006801:Humans; D007536:Isomerism; D008070:Lipopolysaccharides / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D019081:O Antigens / Q000138:chemical synthesis*; D009894:Opportunistic Infections / Q000276:immunology*; D012210:Rhamnose / Q000031:analogs & derivatives / Q000138:chemical synthesis*
chemical_list: D008070:Lipopolysaccharides; D019081:O Antigens; D012210:Rhamnose