title: Lipo-oligosaccharidic antigen from Mycobacterium gastri. Complete structure of a novel C4-branched 3,6-dideoxy-alpha-xylo-hexopyranose.
abstract: The following incomplete structure, alpha-X-(1-->3)-[beta-L-Xylp-(1-->4)]6-3-O-Me-alpha-Rhap-(1- ->3)- beta-D-Galp-(1-->3)-beta-D-Glcp-(1-->4)-2-O-acyl-alpha-D-Glcp-(1<-->1)-4 ,6-di-O-acyl-alpha-D-Glcp, was previously established for the antigenic lipo-oligosaccharide typifying Mycobacterium gastri, namely, LOS-III. The partial structure of the distal monosaccharide (X) was assigned as 3,6-dideoxy-4-C-(1,3-di-O-methylpropyl)-alpha-hexopyranose, which corresponds to a new-found monosaccharide in nature [Gilleron M., Vercauteren J., & Puzo G. (1993) J. Biol. Chem. 268, 3168-3179]. This article reports the complete structure of X, which was determined from the FAB-MS and 2D NMR analysis of the peracetylated LOS-III. The comparative analyses of the native and per-O-acetylated LOS-III FAB-MS spectra revealed, for the monosaccharide X, a molecular mass of 370 Da and five hydroxyl groups that could be acetylated. Additionally, the 1D 1H NMR spectrum of the per-O-acetylated LOS-III showed a dramatically increased dispersion of the protons, which resonated between 3 and 4 ppm in the spectrum of the underivatized LOS-III. Thus, thanks to 2D NMR sequences (COSY, HOHAHA, HMQC, HMQC-HOHAHA, and HMBC), the complete assignment of the 1H and 13C signals was achieved. Starting from the quaternary C4 resonance, the spin system of the C-alkyl chain was assigned, allowing us to propose the following structure, 3,6-dideoxy-4-C-(1,3-dimethoxy-4,5,6,7-tetrahydroxyheptyl)-alpha-x ylo- hexopyranose. The xylo configuration was established from the ROESY spectrum.
authors.affiliation: Laboratoire de Pharmacologie et de Toxicologie Fondamentales du Centre National de la Recherche Scientifique, Département III, Toulouse, France.
authors.forename: M
authors.initials: M
authors.lastname: Gilleron
authors.forename: J
authors.initials: J
authors.lastname: Vercauteren
authors.forename: G
authors.initials: G
authors.lastname: Puzo
mesh_terms: D000107:Acetylation; D000942:Antigens, Bacterial / Q000737:chemistry*; D002240:Carbohydrate Sequence; D006601:Hexoses / Q000737:chemistry*; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000276:immunology; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009161:Mycobacterium / Q000276:immunology*; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D000942:Antigens, Bacterial; D006601:Hexoses; D008070:Lipopolysaccharides; C023708:abequose