Three New Depsipeptides, Homiamides A–C, Isolated from Streptomyces sp., ROA-065

Three new depsipeptides, homiamides A-C (<b>1</b>-<b>3</b>), were isolated from a marine sediment-derived strain of <i>Streptomyces</i> sp., ROA-065. The planar structures of homiamides A-C (<b>1</b>-<b>3</b>) were elucidated using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopic data. The absolute configurations of <b>1</b>-<b>3</b> were deduced from the application of the Marfey's method and GC-MS analysis after formation of the <i>O</i>-trifluoroacetylated (<i>S</i>)-(+)-methyl-2-butyl ester derivatives of amino acids. Compounds <b>1</b>-<b>3</b> exhibited weak anti-bacterial activities against both Gram-positive bacteria and Gram-negative bacteria, with compound <b>1</b> showing MIC values of 32-64 μg/mL. In antifouling assays, compounds <b>1</b> and <b>2</b> displayed moderate activity against <i>Micrococcus luteus</i> KCTC 3063, while compound <b>3</b> exhibited weak activity against all tested bacteria.