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 . Structure elucidation unambiguously suggests that 1 and 2 feature a new cyclopentanone ring A rather than a pyrrolidinone or furanone ring present in 3–5 . All compounds were assayed for PTP1B inhibitory activity, and their hypothetical biosynthetic pathways were proposed.