Thiofrenomycins, new kalafungin-type pyranonaphthoquinone skeleton with sulfide linkage from Streptomyces sp. MM863L-181F9.

Neisseria gonorrhoeae is the bacterium that causes gonorrhea, and multidrug resistance is becoming progressively more severe in many countries. Therefore, limited drugs are available for treatment. It is predicted that further drug resistance will be acquired, making treatment still more difficult, so there is an urgent need to develop new drugs. We discovered three compounds with a new kalafungin-type pyranonaphthoquinone skeleton, thiofrenomycins A-C, that exhibit strong antibacterial activity against N. gonorrhoeae in a culture solution of Streptomyces sp. MM863L-181F9 derived from fallen leaves. The absolute stereochemistry of these compounds was determined using X-ray crystal structure analysis. These substances exhibit minimal inhibitory concentrations of 0.125-16 µg/mL against N. gonorrhoeae.