Smith 降解法，一种从黄芪甲苷制备环黄芪醇的有效方法。

Smith degradation, an efficient method for the preparation of cycloastragenol from astragaloside IV.

机构信息

State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, China.

出版信息

Fitoterapia. 2014 Jun;95:42-50. doi: 10.1016/j.fitote.2014.02.014. Epub 2014 Mar 5.

DOI:10.1016/j.fitote.2014.02.014

PMID:24613799

Abstract

Cycloastragenol (CA) is the genuine sapogenin of astragaloside IV (ASI). This study focuses on the preparation of CA from ASI. Five hydrolysis methods were compared including H2SO4 hydrolysis, HCl hydrolysis, two-phase acid hydrolysis, mild acid hydrolysis, and Smith degradation. Seven hydrolysis products were purified, and five of them were identified as new compounds. The results indicated that Smith degradation was the most effective approach to prepare CA. In contrast, mild acid hydrolysis produced CA at a low yield, accompanied with the artificial sapogenin astragenol. The other three acid hydrolysis methods mainly produced astragenol. Furthermore, the reaction conditions for Smith degradation were optimized as follows: ASI was dissolved in 60% MeOH-H2O solution, oxidized with 5 equiv. NaIO4 for 12h, followed by reduction with 3 equiv. NaBH4 for 4h, and finally acidified with 1M H2SO4 at pH2 for 24h. Under the optimal conditions, CA could be prepared from ASI at a yield of 84.4%.

摘要

环黄芪醇（CA）是黄芪甲苷（ASI）的真正皂甙元。本研究重点从 ASI 中制备 CA。比较了 H2SO4 水解、HCl 水解、两相酸水解、温和酸水解和 Smith 降解等 5 种水解方法。纯化了 7 种水解产物，其中 5 种被鉴定为新化合物。结果表明，Smith 降解是制备 CA 的最有效方法。相比之下，温和酸水解以低产率得到 CA，同时还产生了人工皂甙元黄芪醇。另外三种酸水解方法主要产生黄芪醇。此外，Smith 降解的反应条件优化为：将 ASI 溶解在 60%甲醇-H2O 溶液中，用 5 当量的 NaIO4 氧化 12 小时，然后用 3 当量的 NaBH4 还原 4 小时，最后用 1M H2SO4 在 pH2 酸化 24 小时。在最佳条件下，CA 可从 ASI 中以 84.4%的产率制备。