The structure of the O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O36 containing 3-deoxy-D-manno-oct-2-ulosonic acid

An oligosaccharide that corresponds to the repeating unit of the O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Providencia alcalifaciens O36. Structural studies of the oligosaccharide and O-deacylated lipopolysaccharide were performed using sugar and methylation analyses along with H-1 and C-13 NMR spectroscopy, including 2D H-1,H-1 COSY, TOCSY, ROESY, and H-detected H-1,C-13 HSQC and HMBC experiments. It was found that the O-polysaccharide is built up of linear trisaccharide repeating units containing 2-acetamido-2-deoxyglucose, 6-deoxy-L-talose (L-6dTal), and 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) and has the following structure.