Pleosmaranes A-R, Isopimarane and 20-nor Isopimarane Diterpenoids with Anti-inflammatory Activities from the Mangrove Endophytic Fungus Pleosporales sp. HNQQJ-1.

Pleosmaranes A-R ( 1 - 18 ), 18 new isopimarane-type diterpenoids, together with four known analogs ( 19 - 22 ), were isolated from the mangrove endophytic fungus Pleosporales sp. HNQQJ-1. Their structures and absolute configurations were established by analysis of their spectroscopic data and electronic circular dichroism (ECD) calculations. Compounds 1 - 9 possess an unusual aromatic B ring and a 20-nor-isopimarane skeleton. Compounds 15 - 17 contain a unique 2-oxabicyclo[2.2.2]octane moiety. Compound 18 features an unexpected 2-oxabicyclo[3.2.1]octane moiety. Compounds 8 and 12 exhibited a moderate inhibitory effect against LPS-induced NO production, with IC 50 values of 19 and 25 μM, respectively.