Structure of the O-specific polysaccharide of Proteus vulgaris O15 containing a novel regioisomer of N-acetylmuramic acid, 2-acetamido-4-O-[(R)-1-carboxyethyl]-2-deoxy-D-glucose

An acidic O-specific polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Proteus vulgaris 015 and studied by sugar and methylation analyses along with H-1 and C-13 NMR spectroscopy, including 2D COSY, TOCSY, ROESY, and H-detected H-1, C-13 HMQC experiments. The polysaccharide was found to contain an ether of GlcNAc with lactic acid, and the following structure of the repeating unit was established: --> 3)-alpha-D-GlcpNAc4(R-Lac)6Ac-(1 --> 2)-beta-D-GlcpA-(1 --> 3)-alpha-L-6dTalp2Ac-(1 --> 3)-beta-D-GlcpNAc-(1 --> where L-6dTal and D-GlcNAc4(R-Lac) are 6-deoxy-L-talose and 2-acetamido-4-O-[(R)-1-carboxyethyl]-2-deOXY-D-glucose, respectively. The latter sugar, which to our knowledge has not been hitherto found in nature, was isolated from the polysaccharide by solvolysis with anhydrous triflic acid and identified by comparison with the authentic synthetic compound. Serological studies with the Smith-degraded polysaccharide showed an importance of 2-substituted GlcA for manifesting of the immunospecificity of P. vulgaris O15. (C) 2002 Elsevier Science Ltd. All rights reserved.