Conformational stabilization of the altruronic acid residue in the O-specific polysaccharide of Shigella sonnei/Plesiomonas shigelloides

Complete assignments for the 1H- and the 13C-NMR spectra of the O-specific polysaccharide of S. sonnei/Plesiomonas shigelloides are reported. Evidence is presented that in this polysaccharide both pyranose residues exist preferentially in the 4C1 chair conformation and that the polysaccharide exists in the zwitterion form.