Antifouling Activity of a Dibrominated Cyclopeptide from the Marine Sponge Geodia barretti super(⊥ )

Many sessile suspension-feeding marine organisms rely on chemical defense to keep their surfaces free from fouling organisms. The brominated cyclopeptides barettin (cyclo[(6-bromo-8-entryptophan)arginine]) (1) and 8,9- dihydrobarettin (cyclo[(6-bromotryptophan)arginine]) (2) from the cold-water sponge Geodia barretti have previously displayed settlement inhibition of barnacle larvae in a dose-dependent manner. In this paper, we describe a novel dibrominated cyclopeptide, bromobenzisoxazolone barettin (cyclo[(6- bromo-8-(6-bromobenzioxazol-3(1H)-one)-8-hydroxy)tryptophan)]argin ine) (3), which we have isolated from G. barretti and which displays settlement inhibition of barnacle larvae (Balanus improvisus) with an EC sub(50) value of 15 nM. The chemical structure was determined using MS and 2D-NMR.