Spongiadioxins A and B, two new polybrominated dibenzo-p-dioxins from an Australian marine sponge Dysidea dendyi.

Two new cytotoxic tetrabromodibenzo-p-dioxins, spongiadioxins A (1) and B (2), were isolated from an Australian marine sponge Dysidea dendyi. The structures of these compounds were established by 1D and 2D NMR spectroscopy, X-ray analysis of the methyl ether of spongiadioxin A (3), and synthesis of the methyl ether of spongiadioxin B (4) from diphenyl ether (9) isolated from Dysidea herbacea.