NMR and conformational study of branched oligosaccharides containing 2,3-disubstituted residues of α-L-rhamnose

Abstract

¹H and ¹³C NMR spectra have been recorded and the nuclear Overhauser enhancements (in D₂O), after pre-irradiation of the anomeric protons, have been measured for tri- and tetrasaccharides containing 2,3-disubstituted residues of α-L-rhamnose and the corresponding disaccharides. The proximity of the conformational states of the disaccharide units in these branched oligosaccharides and in the corresponding disaccharides has been shown, on the basis of both the nOe experimental data and theoretical conformational analysis. This conclusion is also confirmed by data for glycosylation effects in the ¹³C NMR spectra of the oligosaccharides. Keywords: branched oligosaccharides, ¹H and ¹³C NMR spectra, conformations.