Four new diterpenes (1-4) were isolated from the leaves of Myrospermum frutescens as minor constituents. Chagresnol (1), 6beta,18-diacetoxycassan-13,15-diene (2), and chagreslactone (3) possess cassane skeletons, while chagresnone (4) exhibits a cleistanthane skeleton. Molecular structures and their relative stereochemistries were elucidated using NMR spectroscopy in combination with UV, IR, and MS spectral data. Although compound 2 was previously reported as a synthetic product, we report its first isolation as a natural product. Derivative products (10-13) were obtained to test their activities against Chagas's disease. In addition, the absolute stereochemistry of the previously isolated cassane diterpene 5 from M. frutescens is presented.

中文翻译：

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多年生黑麦草（Myrospermum frutescens）的新型木薯和leistanthane二萜：木薯二萜系列的绝对立体化学。

从小黑麦草的叶子中分离出四个新的二萜（1-4）作为次要成分。Chagresnol（1），6beta，18-diacetoxycassan-13,15-diene（2）和chagreslactone（3）具有烷骨架，而chagresnone（4）则具有leistanthane骨架。使用NMR光谱结合UV，IR和MS光谱数据阐明了分子结构及其相对立体化学。尽管以前报道化合物2为合成产品，但我们报告其为天然产物而首次分离。获得了衍生产品（10-13）以测试其抗南美锥虫病的活性。此外，还介绍了先前从苦果分支杆菌中分离出的cassane diterpene 5的绝对立体化学。