Motualevic acids A-F, antimicrobial acids from the sponge Siliquariaspongia sp.

Seven new antibacterials, motualevic acids A-F (1-6) and (4E)-(R)-antazirine (7), have been isolated from the marine sponge Siliquariaspongia sp. and their structures elucidated by spectroscopic methods. Motualevic acids A-D are the first glycyl conjugates of the omega-brominated lipid (E)-14,14-dibromotetradeca-2,13-dienoic acid, and motualevic acid F is the first long-chain 2H-azirine 2-carboxylic acid to be found in nature. Carboxylic acid-containing compounds 1 and 6 inhibit the growth of Staphylococcus aureus and methicillin-resistant S. aureus at 1.2-10.9 microg/mL.