Canescones A‒E: Aromatic Polyketide Dimers with PTP1B Inhibitory Activity from Penicillium canescens

Three pairs of enantiomers (±)-canescones A‒C (1‒3), along with a pair of stereoisomers canescones D (4) and E (5), aromatic polyketide dimers bearing unprecedented 5/6/6/6/5 heterocyclic chemical architectures with a rare pentacyclic dihydrobenzo[1,4]dioxine core, were isolated from the fungus Penicillium canescens. The structure elucidation unambiguously suggests 1 and 2 feature a new cyclopentanone ring A rather than a pyrrolidinone or furanone ring in those of 3‒5. All compounds were assayed for PTP1B inhibitory activity, and their hypothetical biosynthetic pathways were proposed.