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In our screening program for antioxidants with 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity, two novel compounds, demethylbisorbibutenolide (1) and trichopyrone (2), were isolated from the fermentation broth of the fungus of USF-4860 strain isolated from a soil sample. The structures of these compounds were determined from spectroscopic evidence. The biosynthetic origin of the carbon atoms of 2 was unambiguously determined by feeding experiments using (13)C-labeled precursors and elucidation of the (13)C-NMR spectrum of (13)C-labeled 2. These studies showed that 2 was derived from five acetates and a methyl group of methionine. In the DPPH-radical scavenging assay, 1 and 2 gave ED(50) values of 149 and 167 muM after standing for 2.0 hr. Compound 2 reacted with the DPPH radical to form reaction product 3 which was determined to be 1-[4-(3,4-dihydro-3-methyl-6-{1,3-pentadienyl}-2,4-dioxo-2H-pyran-3-yl)-phenyl]-1-phenyl-2-picrylhydrazine from spectroscopic evidence.

In our searching program for novel sorbicillin related compounds, three novel compounds, spirosorbicillinols A (1), B (2), and C (3), were isolated from the fermentation broth of the USF-4860 strain isolated from a soil sample. The planar structures of compounds 1-3 were determined from spectroscopic evidence and degradation reaction, and that of 1 was the same as that of 2. The relative stereochemistries of compounds 1-3 were determined by (1)H-(1)H coupling constants, the elucidation of HMBC and NOESY spectra in detail. 1 and 2 were stereoisomers at C8 position, each other. We propose that compounds 1 and 2 were formed by exo and endo intermolecular Diels-Alder reaction between sorbicillinol as a diene and scytolide (proposed precursor-1) as a dienophile, respectively. Similarly, we propose that compound 3 was formed by an endo intermolecular Diels-Alder reaction between sorbicillinol and proposed precursor-2.