Fungal Polyketides with Three Distinctive Ring Skeletons from the Fungus Penicillium canescens 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.