Fungal Polyketides with Three Distinctive Ring Skeletons from the Fungus <i>Penicillium canescens</i> Uncovered by OSMAC and Molecular Networking Strategies

Four unusual polyketides possessing three unambiguous chemical architectures were discovered from the fermentation of Penicillium canescens assisted by the one strain-many compounds (OSMAC) strategy and MS2-based molecular networking. Penicanone (1) is the first naturally occurring polyketide characterized by a 6/6/8 tricyclic carbon skeleton incorporating an unusual bicyclo[5.3.1]­hendecane core. Penicanesones A–C (2–4) are aromatic polyketide dimers simultaneously featuring inconsistent 6/5/5/6 and 6/6/5/6 heterotetracyclic ring cores. Their plausible biosynthetic pathways and screening of biological activity were described here.