Application of new, high-sensitivity, 1H-13C-n.m.r.-spectral techniques to the study of oligosaccharides.

Four n.m.r. methods that are especially useful for characterization of oligosaccharides are applied to the trisaccharide alpha-Neu5Ac-(2----3)-beta-Gal-(1----4)-Glc (1). Three of these are two-dimensional, heteronuclear methods that provide chemical-shift correlation maps having much higher sensitivity than was previously possible, because they rely on indirect observation of 13C via 1H detection. These methods are used to assign, completely, the 1H- and 13C-n.m.r. spectra of both anomers of the trisaccharide. In addition to these two-dimensional methods, a one-dimensional method is used to measure 1H-1H coupling-constants accurately within each sugar ring. The values of the coupling constants thus measured for 1 are evidence that the conformations of the individual sugar rings are not affected by linkage into the trisaccharide.