Phorbaketals L-N, cytotoxic sesterterpenoids isolated from the marine sponge of the genus Phorbas.

Three new sesterterpenoids, phorbaketals L-N (1-3), were isolated from a marine sponge of the genus Phorbas and their complete structures were elucidated via analysis of HRFABMS and NMR spectroscopic data. Phorbaketal N (3) showed potent cytotoxicity against human pancreas cancer cells (IC50=11.4 µM).