(-)-Axinyssene: a novel cytotoxic diterpene from a Japanese marine sponge Axinyssa sp.

[structure: see text] A novel diterpene, (-)-axinyssene, was isolated from the Japanese marine sponge Axinyssa sp. The structure of (-)-axinyssene was determined on the basis of spectroscopic and synthetic evidence to be 1-methyl-4-[(4E)-5',9'-dimethyl-1'-methylene-4',8'-decadienyl]-(4S)-cyclohexene. (-)- and (+)-axinyssene showed mild cytotoxicity against acute promyelocytic leukemia, HL-60 cells.