Three new diterpenoids, plectalibertellenones A–C, isolated from endolichenic fungi Pseudoplectania sp. EL000327

Three new pimarane diterpenoids, plectalibertellenones A−C (1–3), along with six known compounds, 9α-hydroxy-1,8(14),15-isopimaratrien-3,7,11-trione (4), 9α-hydroxy-1,8(14),15-isopimaratrien-3,11-dione (5), phomenone B (6), (−)-pestalotin (7), (+)-pestalotin (8), and 6-pentyl-4-methoxy-pyran-2-one (9) were isolated from the crude extract of an endolichenic fungus, Pseudoplectania sp. EL000327. The planar structures of metabolites 1–3 were elucidated using UV, mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopic data. The relative and absolute configurations of 1–3 were deduced from an interpretation of circular dichroism (CD) spectroscopic data, application of an advanced Mosher's method, DP4+ calculations, and combination of NMR spectroscopic methods. Compounds 1–9 did not display any significant anti-bacterial activity; however, compounds 1–4 were cytotoxic to Caco2 cells, with IC50 values 54.8, 80.7, 76.4, and 19.6 µM, respectively.