Five Tetramic Acid Derivatives Isolated from the Iranian Fungus CCTU A372.

Submerged mycelial cultures of the ascomycete   CCTU A372 were found to produce five previously undescribed tetramic acids, for which we propose the trivial names colposetins A-C (-) and colpomenoic acids A and B ( and ), along with the known compounds penicillide () and monodictyphenone (). The planar structures of - were determined by high-resolution electrospray ionization mass spectrometry (HR-ESIMS) and extensive 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. Their absolute configurations were determined by the combination of electronic circular dischroism (ECD) analysis, -based configurational analysis, and a rotating-frame Overhauser effect spectroscopy (ROESY) experiment. Colposetin B displayed weak antimicrobial activity against and (MIC 67 µg/mL).