New bromotyrosine metabolites from the sponge Aplysinella rhax

Four new bromotyrosine metabolites (3-6) along with the previously describe d compounds psammaplin A (1) and bisaprasin (2) have been isolated from the sponge Aplysinella rhax collected from Guam, Palau, and Pohnpei. Based upo n the results of extensive spectroscopic analysis and chemical reaction, th e structures of psammaplins A(1) (3) and A(2) (4) have been determined to b e a N,N-dimethylguanidium salt of psammaplin A sulfate and its bis-N,N-dime thylguanidium disulfate derivative, respectively. Aplysinellin A (5) posses ses an additional bromotyrosine-derived C-9 unit connected directly to the carbon framework of psammaplin A by a biphenylic Linkage while aplysinellin B (6) is the corresponding cyclic enol ether. These compounds exhibited mo derate cytotoxicity and inhibitory activities against farnesyl protein tran sferase and leucine aminopeptidase. (C) 2000 Elsevier Science Ltd. All righ ts reserved.