Ircinrimanes A-J: ten undescribed rearranged 4,9-friedodrimane merosesquiterpenoids with cytotoxic and anti-inflammatory activities from the marine sponge Ircinia sp.

Ten undescribed rearranged 4,9-friedodrimane merosesquiterpenoids, named ircinrimanes A-J (1-10), were isolated from the marine sponge Ircinia sp., collected in the South China Sea. Their structures and absolute configurations were unambiguously elucidated by a combination of spectroscopic data, DP4 + probability assessments, electronic circular dichroism (ECD) calculations, and Mo₂(OAc)₄ experiment. Compounds 1-4 incorporated benzene rings, compound 1 contains an unusual 2-carbonyl morpholin ring, while compound 2 features a benzoxazole ring. Compounds 5-9 represent sesquiterpenoid quinones with different amino side chains at C-20 and compound 10 contains an ethoxy side chain. It was worth noting that compounds 1-10 exhibit an unusual rearrangement of 4,9-friedodrimane sesquiterpenes. Compounds 2, 5-8 and 10 exhibited cytotoxic activity, while compound 2 showed anti-inflammatory activity in zebrafish.