The structure of the O-specific polysaccharide from Thiobacillus sp. IFO 14570, with three different diaminopyranoses forming the repeating unit

The O-specific polysaccharide, liberated by mild acid hydrolysis of the lipopolysaccharide (LPS-P) from Thiobacillus sp. IFO14570 as isolated from the phenol phase after phenol-water extraction, is shown to have a linear trisaccharide repeating-unit containing three different diamino sugars, namely 2,4-diacetamido-2,4-dideoxyglucuronic acid, 2-acetamidino-4-acetamido-2,4,6-trideoxyglucopyranose, and 2,3-diacetamido-2,3-dideoxyglucuronic acid in the molar ratio of 1:1:1. On the basis of 1H and 13C spectroscopy, including 2D COSY and coherent transfer (RCT)COSY, 1D NOE in the difference mode, and 2D rotating frame NOE(ROESY) the sequence, the type of substitution, and the position of the acetamidino group could be determined. These experiments allowed formulation of the following structure for the O-specific polysaccharide, although the depicted d configuration of the three sugar residues is not yet proven: