Structural studies on the glucose-heptose region of the Proteus mirabilis R core

Abstract

Methylation analysis of the core oligosaccharide of the Proteus mirabilis mutant R4 (derived from serotype 028 was carried out in order to obtain information on the internal (glucose-heptose) region of the P. mirabilis R core. The isolated core oligosaccharide was composed of glucose, L-glycero-D-manno-heptose, 3-deoxy-D-manno-octulosonic acid (dOclA) and phosphorus in a molar ratio of about 1:2:1:1.4. It was methylated either directly or after dephosphorylation. To localize the position of the phosphate substituents, the permethylated product was dephosphorylated with hydrogen fluoride and the oligosaccharide obtained was remethylated using C2H3I. Location of phosphate at C-7 of the terminal heptose was shown by isolation of the sugar phosphate from partial hydrolysates and gas-liquid chromatography/mass spectrometry of the permethylated product. Combining the data of the methylation analysis with the data of an NMR study allows one to formulate the structure of the core oligosaccharide as folllows: (formula: see text).