[Antigenic polysaccharides of bacteria. 19. The structure of the O-specific polysaccharide chain of Alcaligenes faecalis lipopolysaccharide].

On mild acid hydrolysis of Alcaligenes faecalis lipopolysaccharide, the O-specific polysaccharide containing D-rhamnose and D-xylose in the 3:2 ratio was obtained. Solvolysis of the polysaccharide with hydrogen fluoride in methanol resulted in methyl glycoside of a branched tetrasaccharide including three rhamnose and one xylose residues. Smith degradation of the polysaccharide led to the glycoside of disaccharide composed of two rhamnose residues and glycerol. On the basis of identification of the oligosaccharide fragments, methylation, 1H and 13C NMR analysis (including nuclear Overhauser effect data), it was established that the polysaccharide linear chain is a rhamnan, both xylose residues being attached to one of the rhamnose residues as two branches. The repeating unit of the polysaccharide has the following structure: (Formula: see text).