Structure of the O-Polysaccharide of Providencia alcalifaciens 025 Containing an Amide of D-Galacturonic Acid with N~ε-[(R)-l-carboxyethyl]-L-lysine

摘要

An acidic O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Providencia akalifaciens 025 followed by gel-permeation and anion-exchange chromatography. The O-polysaccharide was studied by sugar and methylation analyses along with~1 H and ~(13)C NMR spectroscopy, including two-dimensional correlation~1H,~(13)C HMBC, and ~1H,~1H ROESY experiments both in D2O and, to detect correlations for NH protons, in a 9 : 1 H2O/D2O mixture. An amino acid was isolated from the polysaccharide by acid hydrolysis and identified as N~ε-[(R)-1-carboxyethyl]-L-lysine ("alaninolysine", 2S,<8S-alaLys) by determination of the specific optical rotation and ~(13)C NMR spectroscopy, using the authentic synthetic diastereomers 2S,<8R-alaLys and 2S,8S-alaLys for comparison. The structure of the branched tetrasac-charide repeating unit of the O-polysaccharide was established.