Complete 1H and 13C NMR chemical shift assignments of mono- to tetrasaccharides as basis for NMR chemical shift predictions of oligosaccharides using the computer program CASPER

Abstract

1H and 13C NMR chemical shift data are used by the computer program CASPER to predict chemical shifts of oligo- and polysaccharides. Three types of data are used, namely, those from monosaccharides, disaccharides, and trisaccharides. To improve the accuracy of these predictions we have assigned the 1H and 13C NMR chemical shifts of eleven monosaccharides, eleven disaccharides, twenty trisaccharides, and one tetrasaccharide; in total 43 compounds. Five of the oligosaccharides gave two distinct sets of NMR resonances due to the α- and β-anomeric forms resulting in 48 1H and 13C NMR chemical shift data sets. In addition, the pyranose ring forms of Neu5Ac were assigned at two temperatures, due to chemical shift displacements as a function of temperature. The 1H NMR chemical shifts were refined using total line-shape analysis with the PERCH NMR software. 1H and 13C NMR chemical shift predictions were subsequently carried out by the CASPER program (http://www.casper.organ.su.se/casper/) for three branched oligosaccharides having different functional groups at their reducing ends, namely, a mannose-containing pentasaccharide, and two fucose-containing heptasaccharides having N-acetyllactosamine residues in the backbone of their structures. Good to excellent agreement was observed between predicted and experimental 1H and 13C NMR chemical shifts showing the utility of the method for structural determination or confirmation of synthesized oligosaccharides.