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Highly Rigid Labdane-Type Diterpenoids from a Chinese Liverwort and Light-Driven Structure Diversification

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journal contribution
posted on 17.07.2015, 00:00 by Jinchuan Zhou, Jiaozhen Zhang, Aixia Cheng, Yuanxin Xiong, Lei Liu, Hongxiang Lou
Two unprecedented labdane-type diterpenoids haplomintrins A (1) and B (2) with six rings system were isolated from a Chinese liverwort Haplomitrium mnioides. Light-driven reaction of homologous haplomitrenonolides C (6), A (4), and D (3) afforded haplomintrins A–C (1, 2, and 7), respectively, while 4 was converted to more complex congeners haplomintrins D–G (811) through intramolecular cyclization. Formation of 1 and 2 from compounds 6 and 4, respectively, helps us to postulate that a photochemical reaction is involved in the biosynthetic pathway. These structure features can be used as molecular markers of H. mnioides, and their allelopathic effects are also preliminarily tested.