Oxirapentyns F–K from the Marine-Sediment-Derived Fungus Isaria felina KMM 4639

Six new highly oxygenated chromene derivatives, oxirapentyns F–K (2–7), one new polyketide (8), one new benzofurane (9), and two known cyclodepsipeptides, isoisariin B and isaridin E, were isolated from the lipophilic extract of the marine-derived fungus Isaria felina KMM 4639. The structures of compounds 2–9 were determined using spectroscopic methods. The relative configurations of compounds 2–7 were established through a combination of NOE data and spin coupling constants, and these results were confirmed by X-ray crystallographic analysis of 4. The absolute structures of all oxirapentyns were assumed based on their biogenetic relationship and confirmed using the modified Mosher’s method on 2 and 7. Isariketide (8) showed moderate cytotoxicity toward HL-60 cells.