Structure of a colitose-containing O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O6

The O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Providencia alcalifaciens O6 and studied by sugar and methylation analysis, selective hydrolytic removal of 3,6-dideoxy-l-xylo-hexose (colitose, Col), 1H and 13C NMR spectroscopy, including 2D 1H,1H COSY, TOCSY, ROESY and H-detected 1H,13C HSQC and HMBC experiments. The polysaccharide was found to have a branched pentasaccharide repeating unit with the following structure: Remarkably, the trisaccharide side chain of the O6-polysaccharide represents a colitose ('3-deoxy-l-fucose') analogue of the H type 1 (precursor) antigenic determinant.