Tsavoenones A–C: unprecedented polyketides with a 1,7-dioxadispiro[4.0.4.4]tetradecane core from the lichen Parmotrema tsavoense?
Thuc-Huy Duong, Mehdi A. Beniddir, Grégory Genta-Jouve, Thammarat Aree, Marylène Chollet-Krugler, Jo?l Boustie, Solenn Ferron, Aurélie Sauvager, Huu-Hung Nguyen, Kim-Phi-Phung Nguyen, Warinthorn Chavasiri and Pierre Le Pogam
Abstract
New racemic dispiranic polyketides, tsavoenones A (1), B (2) and C (3), having a novel 1,7-dioxadispiro[4.0.4.4]tetradecane scaffold were isolated from the foliose lichen Parmotrema tsavoense. These compounds were structurally elucidated by extensive NMR analyses, comparison between experimental and theoretical 13C NMR data and X-ray crystallography. A putative biosynthetic scenario for the formation of 1–3 from parmosidone D, a meta-depsidone previously isolated from the same lichen material, was proposed. Tested for its cytotoxicity, 1 displayed a moderate activity against human myelogenous leukemia K562 cell line with an IC50 value of 66 μg mL?1.