Hemiacetalmeroterpenoids A-C and Astellolide Q with Antimicrobial Activity from the Marine-Derived Fungus sp. N-5.

Four new compounds including three andrastin-type meroterpenoids hemiacetalmeroterpenoids A-C (-), and a drimane sesquiterpenoid astellolide Q (), together with eleven known compounds (-) were isolated from the cultures of the marine-derived fungus sp. N-5, while compound was first isolated from a natural source. The structures of the new compounds were determined by analysis of detailed spectroscopic data, and the absolute configurations were further decided by a comparison of the experimental and calculated ECD spectra. Hemiacetalmeroterpenoid A () possesses a unique and highly congested 6,6,6,6,5,5-hexa-cyclic skeleton. Moreover, the absolute configuration of compound was also reported for the first time. Compounds , and exhibited significant antimicrobial activities against and with MIC values ranging from 1.56 to 6.25 μg/mL.