Acremosides A–G, Sugar Alcohol-Conjugated Acyclic Sesquiterpenes from a Sponge-Derived Acremonium Species

Seven new sugar alcohol-conjugated acyclic sesquiterpenes, acremosides A–G (1–7), were isolated from the cultures of the sponge-associated fungus Acremonium sp. IMB18-086 cultivated with heat-killed Pseudomonas aeruginosa. The structures were determined by comprehensive analyses of 1D and 2D NMR spectroscopic data. The relative configurations were established by J-based configuration analysis and acetonide derivatization. The absolute configurations were elucidated by the Mosher ester method and ECD calculations. The structures of acremosides E–G (5–7) featured the linear sesquiterpene skeleton with a tetrahydrofuran moiety attached to a sugar alcohol. Acremosides A (1) and C–E (3–5) showed significant inhibitory activities against hepatitis C virus (EC50 values of 4.8–8.8 μM) with no cytotoxicity (CC50 of >200 μM).