Structure of the O-polysaccharide of Providencia alcalifaciens O2 containing ascarylose and N-(L-alanyl)-D-glucosamine

摘要

The O-polysaccharide was obtained by degradation of the lipopolysaccharide of Providencia alcalifaciens O2 under mild acidic conditions followed by GPC. The polysaccharide was found to contain two unusual components: 3,6-dideoxy-L-arabino-hexose (ascarylose, Asc) and 2-(L-alanyl) amino-2-deoxy-D-glucose (GlcNAla). Ascarylose was partially split off during lipopolysaccharide degradation and could be eliminated completely by selective acid hydrolysis, which also partially cleaved the beta-GalNAc-(1 -> 6) linkage. The following structure of the branched pentasaccharide repeating unit was established by H-1 and C-13 NMR spectroscopy of the O-polysaccharide and O-deacetylated polysaccharide, as well as products of partial acid hydrolysis: