Delitschiapyrone A, a Pyrone-Naphthalenone Adduct Bearing a New Pentacyclic Ring System from the Leaf-Associated Fungus Delitschia sp. FL1581

Delitschiapyrone A (1), an alpha-pyronenaphthalenone adduct with an unprecedented pentacyclic ring system, was isolated from a solid culture of the leaf-associated fungus Delitschia sp. FL1581. The structure of 1 was elucidated by spectroscopic analysis and X-ray crystallography, and its absolute configuration was defined by experimental and calculated ECD. Biosynthetically, the unique 6/6/5/7/6 pentacyclic core of 1 may be formed by an intermolecular DielsAlder-type addition of the precursors derived from (1?R)-2',3'-dihydropyrenocine C (2) and 6-ethyl-2,7-dimethoxyjuglone (3) found to co-occur with 1 in this fungus.