Structure of the O-specific polysaccharide chain of Shigella boydii type 5 lipopolysaccharide: a repeated study

An acidic, partially O-acetylated O-specific polysaccharide was obtained by mild acid degradation of Shigella boydii type 5 lipopolysaccharide and studied by 1H and 13C NMR spectroscopy, including 2D COSY, 13C-1H heteronuclear COSY, 1D NOE, and 2D ROESY experiments, and chemical methods (sugar and methylation analysis, O-deacetylation, carboxyl reduction, solvolysis with anhydrous HF, partial acid hydrolysis, Smith degradation). It was concluded that the polysaccharide has a hexasaccharide repeating unit of the following structure: with the degree of O-acetylation varying over 30–50%. The established structure differs from that proposed recently for the O-specific polysaccharide of the same S. boydii serotype [M.J. Albert et al., Carbohydr. Res., 265 (1994) 121–127].