Two new labdane-class diterpenes, cacofurans A (1) and B (2), have been iso
lated from a sponge Cacospongia sp. Their structures were determined by ana
lyzing spectroscopic data, by chemical transformations, and by X-ray diffra
ction. Cacofurans I and 2 inhibited the development of fertilized sea urchi
n eggs at concentrations of 0.5 and 5 mug/mL and showed an actin-disrupting
effect on the NBT-II cell line at 10 mug/mL.