Zhang Wenxuan, Xue Wenjie, Jia Yuqing, Wen Gang, Lian Xu, Shen Jing, Liu Ailin, Wu Song
State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College Beijing 100050 People's Republic of China
RSC Adv. 2018 Apr 18;8(26):14389-14392. doi: 10.1039/c8ra01606b. eCollection 2018 Apr 17.
(±)-7--galloyltricetiflavan (1a) was synthesized successfully in five steps from the commercially available trihydroxyacetophenone (2) and trimethoxybenzoyl chloride (3). The flavone 4a was prepared in a one-pot reaction and it gave hex--methylflavan 6 followed by acylation and reduction. However, the demethylation of flavan 6, 5--acetylflavan 10 and 5--phenylacetylflavan 11 by BBr gave all the hydrolyzed fragments 7 and 8 as the major products. By contrast, in the same condition, hept--methylflavan 9 could provide the desired product (±)-7--galloyltricetiflavan (1a) in 91% yield. The additional 5--B-Br complex may stabilize the ester bond during the demethylation process.
(±)-7-没食子酰基三刺槐黄素（1a）以市售的三羟基苯乙酮（2）和三甲氧基苯甲酰氯（3）为原料，经五步反应成功合成。黄酮4a通过一锅法反应制备，然后经过酰化和还原得到六甲基黄烷6。然而，黄烷6、5-乙酰基黄烷10和5-苯乙酰基黄烷11用三溴化硼进行脱甲基反应时，所有水解片段7和8都是主要产物。相比之下，在相同条件下，七甲基黄烷9能以91%的产率得到所需产物(±)-7-没食子酰基三刺槐黄素（1a）。额外的5-B-Br配合物可能在脱甲基过程中稳定酯键。
