The chemistry of hop constituents. Part XXVIII. The structure of an autoxidation product of humulone

Abstract

Humulone undergoes rapid aerial oxidation, both in the hop and in solution, to 3-hydroxy-3-(3,4-dihydroxy-4-methylpentanoyl)-5-isovalerylcyclopentane-1,2,4-trione, identified by proton magnetic resonance spectroscopy and degradation with periodate. Its production involves ring-contraction, loss of a side chain, and formation of an acyl side chain, for each of which reactions there are precedents. Unprecedented is the hydroxylation by oxygen of an olefinic double bond in high yield under mild conditions.