New Ophiobolin Derivatives from the Marine Fungus and Their Cytotoxicities against Cancer Cells.

Five new sesterterpenes, 14,15-dehydro-6--ophiobolin K (), 14,15-dehydro- ophiobolin K (), 14,15-dehydro-6--ophiobolin G (), 14,15-dehydro-ophiobolin G () and 14,15-dehydro-()-14-ophiobolin G (), together with four known ophiobolins (-) were isolated from the marine fungus derived from the seaweed sp. collected in Vietnam. The five new ophiobolins were first isolated as ophiobolin derivatives consisting of a fully unsaturated side chain.