Epicoccalone, a coumarin-type chymotrypsin inhibitor, and isobenzofuran congeners from an Epicoccum sp associated with a tree fungus

The bioactivity-guided fractionation of metabolites from an Epicoccum sp. isolated from the fruiting body of the tree fungus Pholiota squarrosa led to the discovery of a new inhibitor of the serine protease alpha-chymotrypsin. The structure of the active compound, epicoccalone (1), was fully elucidated by spectrometric and spectroscopic methods, revealing a coumarin ring system with an unprecedented substitution pattern. Two isobenzofuran-derived co-metabolites were identified that are remarkably similar to the epicoccalone coumarin core, strongly suggesting that these metabolites share the same orsellinic acid like polyketide pathway. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).