Kawakami Susumu
Faculty of Pharmacy, Yasuda Women's University.
Yakugaku Zasshi. 2020;140(3):355-362. doi: 10.1248/yakushi.19-00180.
In our continuing search for secondary metabolites from plants, we investigated the chemical constituents of various Okinawan plants. From the stems and leaves of Croton cascarilloides (Euphorbiaceae), a great number of rare diterpenoids: crotofolanes; crotocascarins A-Q, and new diterpenoids; rearranged nor-crotofolanes: crotocascarins α-γ; a rearranged crotofolane: neocrotocascarin; and a new skeletal diterpenoid: isocrotofolane glucoside were isolated. Their structures were mainly elucidated from NMR spectroscopic evidence. In addition, absolute configurations of crotocascarins A, B, K and O, crotocascarin α and neocrotocascarin were determined by X-ray crystallographic analyses, chiral HPLC analyses of 2-methylbutyric acid in their molecules, application of the circular dichroism rule for the α,β-unsaturated γ-lactone ring, and the modified Mosher's method. The absolute structures of crotofolanes were reported for the first time, and a biosynthetic mechanism for the formation of crotocascarin α and neocrotocascarin from crotocascarin B was proposed. Other interesting compounds, namely diosmarioside H: a dimeric ent-kaurane glycoside from the leaves of Diospyros maritima, and melionosides A-C: megastigmane glucosides with a spiro-ring structure from the leaves of Meliosma lepidota ssp. squamulata were also isolated.
在我们持续探索植物次生代谢产物的过程中，我们研究了各种冲绳植物的化学成分。从巴豆（大戟科）的茎和叶中，分离出了大量罕见的二萜类化合物：巴豆叶烷；巴豆卡司卡林A - Q，以及新的二萜类化合物；重排降巴豆叶烷：巴豆卡司卡林α - γ；一种重排的巴豆叶烷：新巴豆卡司卡林；以及一种新骨架二萜：异巴豆叶烷糖苷。它们的结构主要通过核磁共振光谱证据得以阐明。此外，通过X射线晶体学分析、对其分子中2 - 甲基丁酸的手性高效液相色谱分析、应用α,β - 不饱和γ - 内酯环的圆二色性规则以及改良的莫舍尔方法，确定了巴豆卡司卡林A、B、K和O、巴豆卡司卡林α和新巴豆卡司卡林的绝对构型。首次报道了巴豆叶烷的绝对结构，并提出了从巴豆卡司卡林B形成巴豆卡司卡林α和新巴豆卡司卡林的生物合成机制。还分离出了其他有趣的化合物，即：来自海滨柿叶的二聚对映贝壳杉烷糖苷——地奥马里oside H，以及来自鳞叶泡花树亚种叶的具有螺环结构的巨大戟烷糖苷——美里欧糖苷A - C。
