| Summary: | Chemical investigation of the South-Pacific marine sponge <i>Suberea clavata</i> led to the isolation of eight new bromotyrosine metabolites named subereins 1–8 (<b>2</b>–<b>9</b>) along with twelve known co-isolated congeners. The detailed configuration determination of the first representative major compound of this family 11-<i>epi</i>-fistularin-3 (11<i>R</i>,17<i>S</i>) (<b>1</b>) is described. Their chemical characterization was achieved by HRMS and integrated 1D and 2D NMR (nuclear magnetic resonance) spectroscopic studies and extensive comparison with literature data. For the first time, a complete assignment of the absolute configurations for stereogenic centers C-11/17 of the known members (11<i>R</i>,17<i>S</i>) 11-<i>epi</i>-fistularin-3 (<b>1</b>) and 17-deoxyfistularin-3 (<b>10</b>) was determined by a combination of chemical modifications, Mosher’s technology, and ECD spectroscopy. Consequently, the absolute configurations of all our new isolated compounds <b>2</b>–<b>9</b> were determined by the combination of NMR, Mosher’s method, ECD comparison, and chemical modifications. Interestingly, compounds <b>2</b>–<b>7</b> were obtained by chemical transformation of the major compound 11-<i>epi</i>-fistularin-3 (<b>1).</b> Evaluation for acetylcholinesterase inhibition (AChE), DNA methyltransferase 1 (DNMT1) modulating activity and antifouling activities using marine bacterial strains are also presented.
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