Antibiotic FI-3 is a rare tetramic acid antibiotic first reported in 2010 as a biosynthetic intermediate of the frontalamides by Clardy and co-workers at Harvard. FI-3 is active against Gram positive bacteria including methicillin sensitive and methicillin resistant S. aureus (MIC 32 and 128 µg/mL, respectively). FI-3 disrupts biofilm adherence at 64 µg/mL. FI-3 enhances the activity of tetracycline, gentamicin and vancomycin against S. aureus.