Chemical Structure of the Core Region of Escherichia coli J‐5 Lipopolysaccharide

Abstract

The lipopolysaccharide of Escherichia coli J‐5 was sequentially de‐O‐acylated, dephosphorylated, reduced, de‐N‐acylated, and N ‐acetylated. The products were separated by high‐performance anion‐exchange chromatography into a nonasaccharide (1), two octasaccharides (2,3), and a heptasaccharide (4). Compositional analysis, methylation analysis, and NMR spectroscopy revealed the structures of the products as: (1) (2) (3) (4) in which ¹R is l‐α‐d‐Hepp‐(1–5)‐[α‐Kdop‐(2–4)‐]‐α‐Kdop‐(2–6)‐β‐d‐GlcpNAc‐(1–6)‐d‐GlcN‐Acol, and ²R is l‐α‐d‐Hepp‐(1–5)‐α‐Kdop‐(2–6)‐β‐d‐Glcp NAc‐(1–6)‐d‐GlcNAcol (LD‐Hep, l‐glycero‐d‐manno‐heptose; Kdo, 3‐deoxy‐d‐manno‐octulopyranosonic acid; GlcNAcol, 2‐acet‐amido‐2‐deoxy‐glucitol). Fast‐atom‐bombardment mass spectrometry of de‐O‐acylated and dephosphorylated lipopolysaccharide showed that the isolated oligosaccharides represented the complete carbohydrate moiety of the lipopolysaccharide, and indicated that the non‐reducing terminal d‐GlcN residue in lipopolysaccharide was present as the free base.