Structures and absolute configuration of three α-pyrones from an endophytic fungus Aspergillus niger

Three α-pyrone derivatives, campyrones A–C (1–3), were isolated from Aspergillus niger, an endophytic fungus occurring in Zanthoxylum lemairei leaves. Their structures were elucidated by detailed spectroscopic and spectrometric analyses and confirmed by X-ray diffraction. The absolute configurations were assigned by a combination of circular dichroism (CD) spectra and X-ray analyses. Biosynthetically, pyrophen (4) and the new derivatives may be derived in a mixed biosynthesis from l-phenylalanine (for 4), l-isoleucine (for 1), l-leucine (for 2), and l-valine (for 3) as starter units, respectively. In bioassays, the new compounds exhibited weak toxicity on brine shrimp larvae (Artemia salina).