Abyssomicin Monomers and Dimers from the Marine-Derived <i>Streptomyces koyangensis</i> SCSIO 5802

Three new abyssomicin monomers designated neoabyssomicins D (<b>1</b>), E (<b>2</b>), and A2 (<b>3</b>) and the two dimeric neoabyssomicins F (<b>4</b>) and G (<b>5</b>) were discovered from the marine-derived <i>Streptomyces koyangensis</i> SCSIO 5802, and their structures rigorously elucidated. Neoabyssomicin D (<b>1</b>) possesses an unprecedented 8/5/5/7 ring skeleton, the biosynthesis of which (as well as <b>2</b>) is proposed herein. Additionally, dimeric agents <b>4</b> and <b>5</b> were found to be active against methicillin-resistant <i>Staphylococcus aureus</i> and vesicular stomatitis virus, respectively