A novel cyclodepsipeptide, iso-isariin B (1), and the known isaridin E (2) were isolated from the entomopathogenic fungus Beauveria felina. Their structures were elucidated using MS/MS fragmentation and extensive 2D-heteronuclear NMR. The X-ray structure of isaridin E was obtained, showing two potent intramolecular H bonds and a type-VI turn with the HyLeu¹-Pro² amide bond in a cis conformation. Iso-isariin B (1) was active against the pest-insect Sitophilus spp. with an LD₅₀ value of 10 μg/mL. This observation also gives some clues for ecological interpretation of cyclodepsipeptide production by B. felina.

中文翻译：

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球孢白僵菌的杀虫环肽

从昆虫病原真菌白僵菌中分离到一种新的环二肽，异沙丁烯素B（1）和已知的异沙丁素E（2）。使用MS / MS片段和广泛的2D杂核NMR阐明了它们的结构。获得了异旋蛋白E的X射线结构，显示了两个有效的分子内H键和具有顺式构型的HyLeu ¹ -Pro ²酰胺键的VI型转角。异isariin B（1）对害虫昆虫Sitophilus spp具有活性。LD ₅₀值为10μg/ mL。该观察结果也为生态学解释环糊精的生产提供了一些线索。费利纳（B.felina）。