Methods were developed and optimized for the preparation of the 2,3-cis- and the 10,11-cis-isomers of silybin by the Lewis acid catalyzed (BF3∙OEt2) isomerization of silybins A (1a) and B (1b) (trans-isomers). The absolute configuration of all optically pure compounds was determined by using NMR and comparing their electronic circular dichroism data with model compounds of known absolute configurations. Mechanisms for cis–trans-isomerization of silybin are proposed and supported by quantum mechanical calculations.
方法已经开发和优化,用Lewis酸催化(BF
3∙OEt
2)对
硅基素丙素A (
1a)和B (
1b)(
顺式异构体)进行异构化,制备2,3-
cis和10,11-
cis异构体。所有光学纯化合物的绝对构型通过使用NMR和将它们的电子圆二色性数据与已知绝对构型的模型化合物进行比较来确定。提出了
硅基素丙素
cis–
trans异构化的机理,并得到了量子力学计算的支持。