Peniroquesines A–C: Sesterterpenoids Possessing a 5–6–5–6–5-Fused Pentacyclic Ring System from Penicillium roqueforti YJ-14

Three novel sesterterpenes, peniroquesines A-C, possessing an 5-6-5-6-5-fused pentacyclic ring system, were isolated from the fungus Penicillium roqueforti YJ-14 by solid fermentation. Their structures were initially investigated in detail by NMR spectra and HR-ESI-MS and were further confirmed by chemical reaction experiments as well as by X-ray analysis. Furthermore, a plausible biosynthetic pathway was investigated by isotope-labeling experiments.