Structure of a neutral O-specific polysaccharide of the bacterium Providencia alcalifaciens O5

A neutral polysaccharide containing D-galactose, 2-acetamido-2-deoxy-D-gluc ose, and 3-acetamido-3,6-dideoxy-D-glucose (Qui3NAc) in the ratios 2:1:1 wa s obtained by mild acid degradation of lipopolysaccharide of the bacterium Providencia alcalifaciens O5 followed by gel chromatography and ion-exchang e chromatography or treatment with anhydrous hydrogen fluoride. On the basi s of full acid hydrolysis, methylation, and H-1- and C-13-NMR spectroscopy, including two-dimensional correlation spectroscopy (COSY), total correlati on spectroscopy (TOCSY), H-detected heteronuclear H-1, C-13 single-quantum coherence (HSQC), and nuclear Overhauser effect spectroscopy (NOESY), the f ollowing structure of the linear tetrasaccharide repeating unit of the poly saccharide was established.