Fungal Metabolism of the Prenylated Isoflavone 2,3-Dehydrokievitone

The prenylated isoflavone, 2,3-dehydrokievitone [5,7,2′,4′-tetrahydroxy-8-(3,3-dimethylallyl)- isoflavone, 1], was metabolized by both Aspergillus flavus and Botrytis cinerea to yield the same three compounds, a dihydrofurano-isoflavone (DK-M1, 2), a dihydropyrano-isoflavone (DK- M2, 3), and a glycol (DK-M3, 4). Although structure 3 has previously been assigned to lunatone, an isoflavone from CuCl₂-stressed lima bean (Phaseolus lunatus) seedlings, a comparison of spectroscopic (MS, ¹H NMR) data indicated that the Phaseolus compound was not identical with metabolite DK-M2 found in Aspergillus and Botrytis cultures. Evidence is presented to suggest that lunatone is probably identical with the furano-substituted metabolite DK-M 1 (2).