A novel C20 natural product, acacienone (1), was isolated from the leaves of Acacia mangium collected in Bangladesh. The structure of compound 1 was elucidated by spectral studies and X-ray crystallographic analysis. Acacienone (1) possesses a terpenoid-related tetracyclic framework containing 20 carbons with biogenetically unusual structural features: (i) vicinal C1-branches at the C-3 and C-4 positions in the A ring, and (ii) a cyclopentenone D ring in an androsterone-like assembly, lacking a methyl group at the C-13 position.

中文翻译：

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Acacienone，类萜类天然产物，具有从马占相思叶中分离出的前所未有的C20构架

从孟加拉国收集的马占相思叶子中分离出一种新型的C20天然产物acacienone（1）。通过光谱研究和X射线晶体学分析阐明了化合物1的结构。Acacienone（1）具有与萜类化合物相关的四环骨架，其中含有20个碳，具有生物遗传上不寻常的结构特征：（i）在A环的C-3和C-4位置附近的C1-分支，和（ii）环戊烯酮D环以雄甾酮样的组装形式存在，在C-13位置缺少甲基。