Synthesis of the 2-deoxy analogue of the methyl α-glycoside of the monosaccharide repeating unit of the O-polysaccharide of Vibrio cholerae O:1

Abstract

The serological specificity of pathogenic Gram-negative organisms often resides in one of the structural constituents of their cell-surface lipopolysaccharides, namely the O-specific polysaccharide (O-SP), or the O-antigen. The intracatenary part of the O-SP of the two main strains of Vibrio cholerae O:1, Ogawa and Inaba, is identical and consists [2-4] of a relatively short [3] chain of (1 ~ 2)-linked moieties of 4-amino-4,6dideoxy-a-D-mannopyranose (o-perosamine), the amino groups of which are acylated with 3-deoxy-L-glycero-tetronic acid. Only the Ogawa strain has its nonreducing residue in the O-SP methylated at 0-2. We are interested in understanding the interaction of polysaccharide antigens and antibodies on the molecular level. To obtain information on the involvement of hydrogen bonding in the binding process, we have synthesized specifically deoxygenated fragments of polysaccharides and studied their binding in systems involving, for example, (1 ~ 6)-/3-o-galactanand (1 ~ 6)-a-D-glucan-specific antibodies [5,6]. For similar investigations involving Vibrio cholerae O: 1, we have previously synthesized [7] methyl a-glycosides of the intracatenary repeating unit of the O-PS deoxygenated at each of the theoretically possible positions, namely 3, 2', and 4'. These substances are also useful as specifically deoxygenated models for the nonreducing end-group of both strains of the O-PS of Vibrio cholerae O: 1. To be able to ascertain the occurrence of