Sesterterpenoids Isolated from a Northeastern Pacific Phorbas sp.

Four new sesterterpenoids, ansellone B (4), phorbadione (5), secoepoxyansellone A (6), and alotaketal C (7), have been isolated from specimens of the sponge Phorbas sp. collected in British Columbia, Ansellone B (4) has an unprecedented heterocyclic skeleton featuring an oxocane ring, and secoepoxyansellone A (6) is the first example of the degraded "secoansellane" sesterterpenoid carbon skeleton. Alotaketal C (7) is an activator of cAMP signaling in HEK cells.