Identification of the tetrasaccharide repeating-unit of the Streptococcus pneumoniae type 23 polysaccharide by high-field proton n.m.r. spectroscopy.

One- and two-dimensional 500-MHz 1H-n.m.r. studies of the capsular polysaccharide from Streptococcus pneumoniae type 23 have been used to determine its structure, which was confirmed by limited degradation. The proposed structure (1) differs from those suggested previously and the phosphate group has been located tentatively at position 3 of the glucosyl residue. (Formula: see text).