New azaphilones from the inedible mushroom Hypoxylon rubiginosum.

Fractionation of the methanol extract of the fruit bodies of the xylariaceus ascomycete Hypoxylon rubiginosum resulted in the isolation of three new azaphilone derivatives named rubiginosins A-C (1-3) and a new fatty acid named rubiginosic acid (4), together with three known compounds, entonaemin A (5), daldinin C (6), and orsellinic acid. Their structures were elucidated by 2D NMR, MS, IR, and UV spectra and chemical reaction. The absolute configuration of compound 3 was established by CD spectroscopy. The structure of 4 was confirmed by X-ray crystallographic analysis.