α-Pyrone and Sterol Constituents of , a Fungal Associate of the Lichen .

Four new metabolites, 4--citreoviridin (), auransterol (), and two analogues ( and ) of paxisterol (), together with two known metabolites (15*,20*)-dihydroxyepisterol () and (), were isolated from cultures of the fungal associate, , of the lichen , endemic to California and Baja California. The structures of all compounds were determined by comprehensive spectroscopic and spectrometric methods, as well as single-crystal X-ray diffraction for the determination of the absolute configuration of . Compound showed selective cytotoxicity toward MCF-7 breast and A2780 ovarian cells with IC values of 4.2 and 5.7 μM, respectively.