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

Ten previously undescribed rearranged 4,9-friedodrimane merosesquiterpenoids, designated ircinrimanes A−J (1−10), were isolated from the marine sponge Ircinia sp., collected from the South China Sea. Their structures and absolute configurations were definitively elucidated through a combination of spectroscopic data analysis, DP4⁺ probability assessments, electronic circular dichroism (ECD) calculations, and Mo₂(OAc)₄ experiment. Compounds 1−4 contained benzene rings, with compound 1 featuring an unusual 2-carbonyl morpholin ring, while compound 2 possessed a benzoxazole ring. Compounds 5−9 comprised sesquiterpenoid quinones with distinct amino side chains at C-20, and compound 10 incorporated an ethoxy side chain. Notably, compounds 1−10 demonstrated an unusual rearrangement of 4,9-friedodrimane sesquiterpenes. Compounds 2, 5−8 and 10 demonstrated cytotoxic activity, while compound 2 exhibited anti-inflammatory activity in zebrafish.