For the first time, the complete structure of a lipopolysaccharide (LPS) core region from Salmonella enterica has been identified that is different from the Ra core type generally thought to be present in all Salmonella LPS. The LPSs from two rough mutants and the smooth form of S. enterica sv. Arizonae IIIa O62, which all failed to react with an Ra core type-specific monoclonal antibody and were resistant to phage FO1, were analyzed after chemical modification using monosaccharide analysis, mass spectrometry, and NMR spectroscopy. In the novel core type, the terminal D-GlcNAc residue present in the Ra core type, is replaced by a D-Glc residue. The O-specific polysaccharide is alpha1-->4-linked to the second distal Glc residue of the core. Furthermore, phosphoryl substituents attached to O-4 of L-glycero-D-manno-heptose (Hep) I and II were identified as 2-aminoethyl diphosphate (on Hep I) and phosphate (Hep II). [structure: see text] Abbreviations in Structure I are as follows: Hepp, L-glycero-D-manno-heptopyranose; Kdo, 3-deoxy-D-manno-oct-2-ulopyranosonic acid; PPEA, 2-aminoethyl diphosphate; R, O-specific polysaccharide. The presence of this novel core type in LPS of S. enterica should be taken into account in the development of a general antibody-based diagnostic system for Salmonella.
Lipopolysaccharide from Vibrio cholerae strain H11 (non‐O1) was de‐ O ‐acylated, dephosphorylated, reduced, de‐ N ‐acylated, N ‐acetylated, and the products were separated by high‐performance anion‐exchange chromatography (HPAE). A decasaccharide, 1, was isolated as the major product, representing the core oligosaccharide attached to the reduced GlcN‐disaccharide lipid A backbone. Its structure was established by compositional and methylation analyses, and extensive NMR investigations including 1 H, 1 H correlation spectroscopy (COSY), total correlation spectroscopy (TOCSY), and nuclear Overhauser enhancement spectroscopy (NOESY), as well as heteronuclear 13 C, 1 H COSY. In another reaction sequence the lipopolysaccharide was hydrolysed with dilute acetic acid and reduced with NaBH 4 . The resulting core fractions were separated by HPAE giving seven individual octasaccharides differing at the reducing 3‐deoxy‐D‐ manno ‐octulosonic acid (Kdo) residue. A major product, 2, was isolated and investigated by the same methods as described for the decasaccharide 1. The following structures are proposed for compounds 1 and 2: image where R is α‐Kdo p ‐(2–6)‐β‐D‐GlcNAc p ‐(1–6)‐D‐GlcNAcol in 1 and 4,8‐anhydro‐Kdool in 2, and Hep is L‐ glycero ‐D‐ manno ‐heptose. In lipopolysaccharide, the terminal residue of α‐D‐glucosamine possessed a free amino group, as proved by deamination with nitrous acid and the 1 H‐NMR spectrum of de‐ O ‐acylated lipopolysaccharide. The conformational preferences of the terminal core heptasaccharide was assessed by Monte Carlo simulations combined with restrained calculations of side chains based on experimentally determined proton‐coupling constants. These calculations, confirmed by NOE data, displayed several long‐range interactions, which resulted in a well‐defined three‐dimensional structure of the core oligosaccharide.
Abstract The coupling of benzoylated glucosyl bromides with 2,3,4,6-tetra-O-benzylated gluco, manno or gulucto-pyranoses promoted by silver triflate is described, and the compositions of the crude reaction mixtures, determined by 13C NMR spectroscopy, are presented. Unsymmetrical trehalose derivatives can be synthesized by such couplings. However, the inherent formation of dimerization products of the reactants reduces the versatility of the reactions. The synthesis of α-d-glucopyranosyl α-l-glucopyranoside and α-d-glucopyranosyl β-l-glucopyranoside is also described.
Abstract Aus der arabino‐Hexenopyranose (Ia) entstehen bei Behandlung mit HF in benzolischer Lösung das Fluorid (II) (Anomerengemisch) und bei Behandlung mit wasserfreiem HF über (II) das Fluorid (III) (Anomerengemisch), das bei Reaktion mit Methanol in Gegenwart von Bortrifluorid die anomeren Glykoside (IV) und (V) ergibt.
