Structural Analysis of Glycans by NMR Chemical Shift Prediction

Structural determination of N- and O-linked glycans as well as polysaccharides is hampered by the limited spectral dispersion. The computerized approach CASPER, an acronym for computer assisted spectrum evaluation of regular polysaccharides, uses liquid state NMR data to elucidate carbohydrate structure based on agreement with predicted 1H and 13C chemical shifts. We here demonstrate developments based on multiple through-bond J-based correlations that significantly enhance the credence to the sequence connectivities proposed in the analysis exemplified by an oligosaccharide and a bacterial polysaccharide. The approach is also suitable for predicting 1H and 13C NMR chemical shifts of synthesized oligosaccharides and glycoconjugates, thereby corroborating a proposed structure.