Triumphalone, a diketone from the volatile oil the leaves of Melaleuca triumphalis, and its spontaneous conversion into isotriumphalone

Joseph J. Brophy, University of New South Wales
Donald C. Craig, University of New South Wales
Robert J. Goldsack, University of New South Wales
Christopher JR Fookes
David N. Leach, Southern Cross University
Peter G. Waterman, Southern Cross University

Abstract

The major component (35–65%) of the volatile oil obtained by steam distillation of the leaves of Melaleuca triumphalis has been identified as (rel)-1b-pentyl-1a,6a-dihydroxy-3,3,5,5-tetramethylcyclohexa-2,4-dione (trivial name triumphalone). Relative stereochemistry was established by nuclear Overhauser experiments and X-ray studies on the 2-(3,5-dinitrobenzoic acid) derivative. The remainder of the oil was composed of mono- and sesquiterpene hydrocarbons and alcohols. On prolonged standing the presence of a rearrangement product of triumphalone was observed which was characterized as (rel)-1b-pentyl-1a,3a-dihydroxy-4,4,6,6-tetramethylcyclohexa-2,5- dione (trivial name isotriumphalone), presumably arising from an acid catalyzed shift of the pentyl group from C-1 to C-2.