Identification of Oxaphenalenone Ketals from the Ascomycete Fungus Neonectria sp.

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• 作者：Jinwei Ren ; Shubing Niu ; Li Li ; Zhufeng Geng ; Xingzhong Liu ; Yongsheng Che
• 刊名：Journal of Natural Products
• 出版年：2015
• 出版时间：June 26, 2015
• 年：2015
• 卷：78
• 期：6
• 页码：1316-1321
• 全文大小：348K
• ISSN：1520-6025

文摘

Neonectrolides B鈥揈 (4鈥?b>7), four new oxaphenalenone ketals incorporating the new furo[2,3-b]isochromeno[3,4,5-def]chromen-11(6aH)-one skeleton, were isolated from the fermentation extract of the ascomycete fungus Neonectria sp. in an in-depth investigation guided by HPLC fingerprint and a cytotoxicity assay. The previously identified oxaphenalenone spiroketal neonectrolide A (1) and its putative biosynthetic precursors (2 and 3) were also reisolated in the current work. The structures of 4鈥?b>7 were primarily elucidated by interpretation of NMR spectroscopic data, and the absolute configurations were deduced by electronic circular dichroism calculations. Compound 6 showed cytotoxic effects against four of the six human tumor cell lines tested. Biosynthetically, compounds 4鈥?b>7 could be derived via the Diels鈥揂lder reaction cascades starting from derivatives of the co-isolated metabolites 2 and 3.