Terpenoids from the Marine-Derived Fungus sp. RR-YLW-12, Associated with the Red Alga .

Two new meroterpenoids, aspermeroterpenes D and E ( and ), two new ophiobolin-type sesterterpenoids, the C-18 epimers of 18,19-dihydro-18-methoxy-19-hydroxyophiobolin P ( and ), and two new drimane-type sesquiterpenoids, 3-hydroxystrobilactone A () and 6--strobilactone A (), along with 11 known terpenoids (- and -) were isolated from the cultures of the algicolous fungus sp. RR-YLW-12, derived from the red alga . The structures and relative configurations of new compounds were established by detailed spectroscopic analysis of NMR and HRMS experiments, and the absolute configurations were assigned by X-ray diffraction experiments and comparison of their experimental and calculated ECD spectra. Compound features a rare 6/6/6/6/5 pentacyclic system with a meroterpenoid skeleton, and the structure of terretonin E () was revised in this study. Compound showed significant inhibitory activities against three microalgae, , , and , with IC values of 10.5, 5.2, and 3.1 μg/mL, respectively.