Acylated oligosaccharides from Klebsiella K63 capsular polysaccharide: depolymerization by partial hydrolysis and by...

The extracellular polysaccharide from Klebsiella K63 is unique in having acetic and formic ester groups attached to the D-galactopyranosyluronic residues in the trisaccharide repeating-sequence. These O-acyl substituents are shown to be somewhat resistant to mild hydrolysis by both acid and alkali. Bacteriophage-induced depolymerization of the polysaccharide generated a series of acylated oligosaccharides comprising one, or more, repeating unit(s). By mild hydrolysis with acid, the same series of oligomers was released from the polysaccharide, together with the corresponding non-acylated compounds and the expected acylated and non-acylated aldobiouronic acids. A study of these oligosaccharides, as well as of a number of their related compounds, is described, with particular emphasis on the methods used to locate the formic and acetic ester groups. The location of the O-acyl substituents on the galactosyluronic residues was further supported by the results obtained from the high-resolution, 400-MHz, p.m.r. spectra and 13C-n.m.r. spectra of a number of the oligosaccharides.