Two new minor polybrominated dibenzo-p-dioxins from the marine sponge Dysidea dendyi.

Two new minor tribromodibenzo-p-dioxins, spongiadioxin C (1) and its methyl ether (2), were isolated from an Australian marine sponge Dysidea dendyi, together with the known minor metabolites methyl ethers of spongiadioxins A (4) and B (6) and polybrominated diphenyl ethers (7-9). The structures of the new compounds were established by 1D and 2D NMR spectroscopy and confirmed by synthesis of 2 from diphenyl ether 9. All isolated compounds inhibited the cell division of fertilized sea urchin eggs.