Verrulactone C with an unprecedented dispiro skeleton, a new inhibitor of Staphylococcus aureus enoyl-ACP reductase, from Penicillium verruculosum F375

An highly quaternary and unprecedented dispiro compound, verrulactone C (1), with the known compound, altenuisol (2), were isolated from a culture broth of the fungal strain Penicillium verruculosum F375. Verrulactone C and altenuisol showed FabI-selective inhibition. Especially, altenuisol had the high correlation between FabI-inhibition and whole cell antibacterial activity against S. aureus and MRSA with MICs of 8-32 μg/mL.