Oxirapentyns F–K from the Marine-Sediment-Derived Fungus <i>Isaria felina</i> KMM 4639

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