A new derivative of phorbaketals isolated from a Marine Sponge Phorbas species

A new sesterterpenoid, phorbaketal derivative, was isolated from the marine sponge Phorbas species. Its planar structures was completely determined from a combination of extensive 1D and 2D NMR experiments and MS data, and also the stereochemistry on the chiral centers were established by the ROESY experiment and the comparison with the and chemical shifts of the known phorbaketal compounds. This compound 1 moderately showed cytotoxicity effect against hepatoma cancer HepG2 cell.