Structural studies of the capsular polysaccharide produced by Leuconostoc mesenteroides ssp. cremoris PIA2

The structure of the capsular polysaccharide (CPS) produced by Leuconostoc mesenteroides ssp. cremoris PIA2 has been determined using component analysis and NMR spectroscopy. (1)H and (13)C resonances were assigned using 2D NMR experiments, and sequential information was obtained by (1)H,(1)H-NOESY and (1)H,(13)C-HMBC experiments. The CPS consists of linear pentasaccharide repeating units with the following structure: →3)-β-D-Galf-(1→6)-β-D-Galf-(1→2)-β-D-Galf-(1→6)-β-D-Galf-(1→3)-β-D-Galp-(1→, in which four out of the five sugar residues have the furanoid ring form, a structural entity found in bacteria but not in mammals. The analysis of the magnitude of the homonuclear three-bond coupling constants of the anomeric protons for the five-membered sugar rings indicates that the sugar residues substituted at a primary carbon atom show one kind of conformational preferences, whereas those substituted at a secondary carbon atom show another kind of conformational preferences.