一维SEMDY和旋转坐标NOE差谱NMR新技术用于天然化合物中寡糖的结构研究

摘要

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-L[WTBZ]-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.%报告从日本续断根部的乙醇提取物中分得二个新的五糖三萜皂甙，应用一维SEMDY和旋转坐标NOE差谱等NMR新技术互相配合的方法对它们的结构进行了研究，确定为：3-O-α-L-吡喃鼠李糖（1→3）-β-D-吡喃葡萄糖（1→3）-α-L-吡喃鼠李糖（1→2）-α-L-吡喃阿拉伯糖-常春藤甙元-28-O-β-吡喃葡萄糖酯甙（1），和3-O-[β-D-吡喃葡萄糖（1→4）]rn[α-L-吡喃鼠李糖（1→3）]-β-D-吡喃葡萄糖（1→3）-α-L-吡喃鼠李糖（1→2）-α-L-吡喃阿拉伯糖-齐墩果酸（2）·结果表明，一维SEMDY和旋转坐标NOE差谱技术互相配合的方法测定寡糖链结构十分有效，高度重叠的糖基1H-NMR信号可按一定规律分离，容易鉴别，糖基之间的连接顺序和连接位置可以准确测定，不需要对化合物进行化学降解或衍生化。