Annotinolides A-C, Three Lycopodane-Derived 8,5-Lactones with Polycyclic Skeletons from Lycopodium annotinum
Yu Tang1, Juan Xiong1, Jing-Jing Zhang2
1Department of Natural Products Chemistry, School of Pharmacy, Fudan University , Shanghai 201203, China.
Abstract:
Three novel 7,8-seco-lycopodane-derived 8,5-lactones (annotinolides A-C, 1-3) were isolated from Lycopodium annotinum. Their structures were elucidated by spectroscopic methods and single-crystal X-ray diffraction. Compound 1 possesses an unusual cyclopropane ring constructed through a hitherto unknown C-6/C-12 bond. Compound 2 represents the first 7,8-seco-lycopodane-derived alkaloid with a rare cyclobutane ring formed by a new C-12/C-15 linkage, while the C-8/C-15 bond remains. Compound 3 contains an unprecedented 12-spiro-9,12-γ-lactone moiety. Their plausible biosynthetic pathways and antiaggregation effects on amyloid-β1-42 are also presented.
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