Flavimycins A and B, dimeric 1,3-dihydroisobenzofurans with peptide deformylase inhibitory activity from Aspergillus flavipes

Flavimycins A (1) and B (2), novel dimeric 1,3-dihydroisobenzofurans, were isolated as inhibitors of peptide deformylase from cultures of Aspergillus flavipes. Their chemical structures were established by NMR and MS data analysis. Compounds 1 and 2 exist as epimeric mixtures at C-1 through fast hemiacetal-aldehyde tautomerism. Compounds 1 and 2 inhibited Staphylococcus aureus peptide deformylase with IC?? values of 35.8 and 100.1 μM, respectively. Consistent with their PDF inhibition, 1 showed two times stronger antibacterial activity than 2 on S. aureus including MRSA, with MIC values of 32-64 μg/mL.