The Structure Determination of Oligosaccharide Chains in Naturally Occurring Compounds by 1D-SEMDY and NOE Difference Spectroscopy in Rotating Frame

Two new saponins containing five sugars have been isolated from the ethanol extract of the root of Dipsocus japonicus and their structures established as(3-O-α-L-rhammopyranosyl(1→3)- α-D-glycopyranosyl(1→3)-α-L-rhammopyranosyl(1→2）-α-L-arabinopyranosyl-hederagenin-28-O-α-D-glycopranoside(1)and3-O-α-D--glycopyranosyl(1→4) α-L-rhamnopyranosyl(1→3)- α-D-glycopyranosyl(1→3)- α-LWTBZ-rhamnopyranosyl(1→2)- α-L-arabinopyranosyl-oleanoic acid(2).Two new NMR techniques,1D-SEMDY and NOE difference spectroscopy in rotating frame have been successfully used to determine the chemical structure of oligosaccharide chains of the saponins.The results obtained showed that the sites of glycosylation and the sequence of sugars in the saponins can be determined unambiguously and total assignment of severely overlapping pro~ton resonance of sugar residues were achieved,without having recourse to chemical degration or modification.