The Structure of the Lipid A‐Core Region of the Lipopolysaccharides from Vibrio cholerae O1 Smooth Strain 569B (Inaba) and Rough Mutant Strain 95R (Ogawa)

The lipopolysaccharides (LPS) from Vibrio cholerae 95R, a rough mutant strain of O1 V. cholerae 162 (Ogawa), and from smooth O1 V cholerae 569B (Inaba) were de‐O‐acylated. In each case, one part of the products was treated with 48% aqueous HF which removed the phosphoryl and fructose residues, then reduced, de‐N‐acylated, and N‐acetylated. Another part was de‐N‐acylated by treatment with hot KOH. The products of both degradation pathways were separated by high‐performance anion‐exchange chromatography. The major dephosphorylated and defructosylated product 1 was obtained in pure form, whereas the minor products 2 and 3 were eluted as a mixture, as were, from the second degradation, the phosphorylated oligosaccharides 4 (major product) and 5 (minor product). No phosphorylated component corresponding to oligosaccharide 3 could be identified by NMR spectroscopy in the latter mixture. The following structures of oligosaccharides 1–5 were established on the basis of monosaccharide and methylation analyses, Smith degradation, and 1 H‐ and 13 C‐NMR investigations (correlated, total correlated, NOE and heteronuclear correlation spectroscopy; all sugars are present as α‐ d ‐pyranoses except where indicated otherwise; Hep, l ‐ glycero ‐ d ‐ manno ‐hsptose; Kdo, 3‐deoxy‐ d ‐ manno ‐2‐octulosonic acid).In the untreated lipopolysaccharide, the amino group of the non‐reducing terminal glucosamine residue is not substituted.