Rubrolide R: a new furanone metabolite from the ascidian Synoicum of the Indian Ocean.

A new furanone metabolite of the rubrolide family, rubrolide R as diacetate (1), was isolated from a new species of the ascidian Synoicum, besides the known compounds rubrolide A (as diacetate), cadiolide B and prunolide A. The structure of the new rubrolide was elucidated by a study of spectral data. The crude extract and isolated compounds (prunolide A and cadiolide B) showed antiviral activity against the Japanese encephalitis virus. Prunolide A showed cytotoxic activity against breast cancer cell lines at a concentration of < 1 μM.