Synthesis and biological evaluation of two naturally-occurring bromotyramines, moloka'iamine 1 and 3,5-dibromo-4-methoxy-beta-phenethylamine 2, together with several analogues, have been completed. Bromotyramine 2 is cytotoxic, and was found to be a potent antifoulant. Analogues 15 and 16 also displayed significant cytotoxic and antifouling activities.