Determination of the structure of three oligosaccharides from normal human urine by using 60-MHz, carbon-13 nuclear magnetic resonance spectroscopy.

The detailed structures of three trisaccharides obtained from normal, human urine were determined by 13C-nuclear magnetic resonance spectroscopy. These compounds are alpha-NeuAc-(2 leads to 3)-beta-D-Gal-(1 leads to 4)-D-Glc, alpha-NeuAc-(2 leads to 6)-beta-D-Gal-(1 leads to 4)-D-GlcNAc (2), and alpha-NeuAc(2 leads to 3)-beta-D-Gal-(1 leads to 4)-D-GlcNAc (3). Trisaccharide 3 has not previously been reported in normal, human urine. The elucidation of these structures by using 13C-n.m.r. spectroscopy is discussed in detail. Some unusual, chemical-shift values found for structure 2 are related to intramolecular interactions between the NeuAc and GlcNAc residues, and may indicate that 2 has a unique conformation. The potential use of these trisaccharides as model compounds in 13C-n.m.r.-spectral studies of intact glycoproteins is critically evaluated. Like 1H-n.m.r. spectroscopy, this technique demonstrates elucidation of the structures of mixtures of oligosaccharides or of glycopeptides that have very closely related structures.