The structure of the O‐antigenic polysaccharide from lipopolysaccharide of Vibrio cholerae strain H11 (non‐O1)

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Abstract
After acid degradation of the lipopolysaccharide (LPS) of Vibrio cholerae strain H11 (non‐O1), a tetrasaccharide was obtained, the structure of which was determined by quantitative and methylation analyses, periodate oxidation, one‐ and two‐dimensional NMR spectroscopy, and fast‐atom‐bombardment and four‐sector tandem mass spectrometry as β‐d‐GalANGro‐(1–3)‐β‐d‐QuiNAc‐(1–4)‐α‐d‐GalANGro‐(1–4)‐NeuAc, in which GalANGro is N‐galacturonoyl‐2‐aminoglycerol and QuiN 2‐amino‐2,6‐dideoxy‐glucopyranose. In addition, the trisaccharide β‐d‐GalANGro‐(1–3)‐β‐d‐QuiNAc‐(1–4)‐d‐altro‐heptulose and the disaccharide α‐d‐GalANGro‐(1–4)‐NeuAc were isolated from acid‐degraded lipopolysaccharide; the occurrence of sedoheptulose in lipopolysaccharide has not been described before. Based on the result of methylation analysis showing that galacturonic acid was the terminal sugar of the polysaccharide chain, and on the assumption that the tri‐ and the disaccharide represented the reducing and the non‐reducing ends of the polysaccharide, respectively, the chemical structure of the O‐specific chain of V. cholerae H11 is proposed as α‐d‐GalANGro‐(1–4)‐α‐NeuAc‐(2–3)‐β‐d‐GalANGro‐(1–3)‐β‐d‐QuiNAc‐(1‐[4)‐α‐d‐GalANGro‐(1–4)‐α‐NeuAc‐(2–3)‐β‐d‐GalANGro‐(1–3)‐β‐d‐QuiNAc‐(1‐]n‐(1–4)‐d‐altro‐heptulose. However, other possible structures can not be ruled out since the tri‐ and the disaccharide could be localised at different positions.