Glioperazine B, as a new antimicrobial agent against Staphylococcus aureus, and glioperazine C: two new dioxopiperazines from Bionectra byssicola.

In the course of our screening for new antibacterials from microbial metabolites, two new dioxopiperazine metabolites, glioperazines B (1) and C (2), together with the known compound, glioperazine (3), were isolated from the mycelia of a liquid fermentation culture of the fungus, Bionectra byssicola F120. The structures of compounds 1 and 2 were assigned on the basis of MS and NMR data. Compound 1 is an unusual dioxopiperazine metabolite containing an OMe group at the alpha-carbon of the amino acid residue. Compound 1 showed weak antibacterial activity against various strains of S. aureus, including methicillin-resistant S. aureus (MRSA) and quinolone-resistant S. aureus (QRSA), while 2 and 3 did not show such activity.