采用动态NMR对8-C-glucosyl-prunetin构象研究

采用动态NMR方法,对从海南黄檀中分得的8-C-glucosyl-prunetin及其它7位 上羟基烷基化了的8－C苷异黄酮的构象进行了研究。结果表明,在8－C苷异黄酮中 ,当7位上羟基烷基化了时,由于1"-C(sp~3)-8C(sp~2)单键旋转受阻,产生两种构 象异构体。同时,借助分子力场（MM）计算方法,确定了8-C-glucosyl-prunetin 两种构象异构栓中的优势构象,即为1"-H与7－OCH_3位于同侧。由低能量构象转化 为高能量构象所需活化能为75.66 kJ/mol。这一结果与动态NMR实验计算的71. 48kJ/mol活化自由能数值相符。

Conformational Study on 8-C-glucosyl-prunetin by Dynamic NMR Spectroscopy

By means of variable temperature dynamic NMR spectra, conformation of 8-C-glucosyl prunetin, isolated from the leaves of Dalbergia hainanensis (Leguminosae), and other 8-C-glucosyl flavones was studied. The restricted rotation around the 1"-C(sp3)-8-C(sp2) bond in the C-glucosides isoflavonoid results in two main conformers (syn and anti). With the help of Molecular Mechanics (MM) calculation, the preferred conformation A of 8-C-glucosyl prunetin has 1"-H gauche to the 7-OCH3. The barrier to rotation was 75.66 kJ/mol. This result agrees with the calculated value 71.48 kJ/mol of free energy of activation for the interconversion between the conformers.