Structure of the O-specific polysaccharide of hafnia alvei 1204 containing 3,6-dideoxy-3-formamido-D-glucose

The O-specific polysaccharide of Hafnia alvei strain 1204 has a hexasaccharide repeating unit containing D-mannose, D-glucuronic acid, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, and 3,6-dideoxy-3-formamido-D-glucose (Qui3NFo) in the ratios 2:1:1:1:1 as well as O-acetyl groups. On the basis of methylation analysis of the intact, carboxyl-reduced, and Smith-degraded polysaccharide as well as 1D and 2D NMR spectroscopy, including 1D total correlation spectroscopy, 1D NOE spectroscopy, 2D homonuclear shift-correlated spectroscopy (COSY), and 13C, 1H heteronuclear COSY, the following structure of the O-deacetylated polysaccharide was established: →3)-α-d-Manp-(1→2)-α-d-Manp-(1→3)-β-d-GlcpNAc-(1→→2)-β-d-Quip3NFo-(1→3)-α-d-GalpNAc-(1→4)-α-d-GlcpA-(1→ Location of the N-formyl group, occurring as two stereoisomers in the ratio ∼ 3:1, was determined by an NOE on H-3 Qui3N arising on pre-irradiation of HCO of the minor (E) isomer.