Ianthesines A–D, Four Novel Dibromotyrosine-Derived Metabolites from a Marine Sponge, Ianthella sp.

Novel dibromotyrosine-derived metabolites, ianthesines A, B, C, and D, were isolated from an Australian marine sponge of the genus Ianthella sp. Their structures were elucidated using chemical and spectroscopic techniques. Ianthesines A, B, and D were derived from two dibromotyrosines. Ianthesine C is a tetramer possessing eight bromine atoms and its molecular weight is 1606. Ianthesines B–D showed Na,K-ATPase inhibitory activity in the range of 50–440 μM, whereas ianthesine A is inactive.