Structure of the O-specific polysaccharide of the lipopolysaccharide of Azospirillum brasilense Sp245

An O-specific polysaccharide was isolated from the lipopolysaccharide of a plant-growth-promoting bacterium Azospirillum brasilense Sp245 and studied by sugar analyses along with one- and two-dimensional 1H and 13C NMR spectroscopy, including NOESY. The polysaccharide was found to be a new rhamnan with a pentasaccharide repeating unit having the following structure:→2)-β-d-Rhap-(1→3)-α-d-Rhap-(1→3)-α-d-Rhap-(1→2)-α-d-Rhap-(1→2)-α-d-Rhap-(1→