α‐2→4‐Interlinked 3‐deoxy‐ d ‐manno‐octulosonic acid disaccharide

After mild acid hydrolysis, a disaccharide of 3-deoxy-D-manno-octulosonic acid (dOclA) was obtained from Re-mutant lipopolysaccharide of Salmonella minnesota, Salmonella godesberg, Proteus mirabilis, and Escherichia coli, and from the lipopolysaccharide of an S. minnesota Rb2 mutant. Combined gas-liquid chromatography/mass spectrometry of the reduced and permethylated derivatives indicated that the disaccharide is interlinked by a 2----4-glycosidic bond in all lipopolysaccharides tested. In addition, it was shown by gas-liquid chromatography of appropriate synthetic standards and a previously characterized alpha 2----4-linked dOclA disaccharide (derived from lipopolysaccharide of S. godesberg) that the non-reducing dOclA residue possesses the alpha configuration. In the case of lipopolysaccharide of S. minnesota Rb2 mutant, this result, together with earlier findings, suggests that it contains a linear dOclA trisaccharide of the sequence dOclA(alpha 2-4)dOclA. The results show that a dOclA(alpha 2-4)dOclA disaccharide represents a common architectural principle in enterobacterial lipopolysaccharides.