Pyrazolofluostatins A–C, Pyrazole-Fused Benzo[a]fluorenes from South China Sea-Derived Micromonospora rosaria SCSIO N160

Pyrazolofluostatins A–C (13), three new benzo­[a]­fluorenes with an unprecedented carbon skeleton, were obtained from the South China Sea-derived Micromonospora rosaria SCSIO N160. Their structures were elucidated by extensive spectroscopic analyses. The structure of pyrazolofluostatin A (1) was confirmed by X-ray crystallographic analysis. Notably, 13 possessed a benzo­[cd]­indeno­[2,1-f]­indazol skeleton with a pyrazole-fused 6/5/6/6/5 pentacyclic ring system. Pyrazolofluostatin A (1) showed moderate antioxidation activity (EC50 48.6 μM).