Structure of the O-specific polysaccharide of Proteus vulgaris O4 containing a new component of bacterial polysaccharides, 4,6-dideoxy-4-{N-[(R)-3-hydroxybutyryl]-L-alanyl}amino-D-glucose

A high-molecular-mass O-specific polysaccharide was obtained by mild acid degradation of Proteus vulgaris O4 lipopolysaccharide followed by GPC. The polysaccharide was studied by chemical methods along with H-1 and C-13 NMR spectroscopy, including two-dimensional COSY, TOCSY, NOESY, H-detected H-1,C-13 HMQC, and H-1,C-13 HMBC experiments. Solvolysis of the polysaccharide with trifluoromethanesulfonic (triflic) acid resulted in a GlcpA-(1 --> 3)-GlcNAc disaccharide and a novel amino sugar derivative, 4,6-dideoxy-4-{-[(R)-3-hydroxybutyryl]-L-alanyl) amino-D-glucose [Qui4N(HbAla)]. On the basis of the data obtained, the following structure of the tetrasaccharide repeating unit of the O-specific polysaccharide was established: --> 4)-beta -D-GlcpA-(1 --> 3)-beta -D-GlcpNAc-(1 --> 2)-beta -D-Quip4N(HbAla)-(1 --> 3)-alpha -D-Galp -(1 --> This structure is unique among the O-specific polysaccharides, which is in accordance with classification of the strain studied in a separate Proteus serogroup. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.