Terpenoid chemistry. XX. Myoporone and dehydromyoporone, toxic furanoid ketones from Myoporum and Eremophila species

Abstract

Certain samples of essential oils from Myoporum deserti, M. betcheanum, M. acuminatum, Eremophila maculata, and E. latrobei have been shown to contain myoporone and/or 10,ll-dehydromyoporone. The ambiguity regarding the stereochemistry of myoporone (previously known from M, bontioides) has been resolved,(-)-myoporone being shown to possess the S configuration by degradation to (S)-(+)-2-methylglutaric acid. (-)-Dehydromyoporone, m.p. 32.5-33.5, [x]D ? 15�, has the S configuration as shown by degradation to (S)-(-)-3-methyladipic acid and hydrogenation to (S)-(-)-myoporone, m.p. 17.5-19�, [x]D-5.3�. Both ketones activate the typical ngaione pathology on intraperitoneal injection into mice but myoporone is not toxic to sheep. Myoporone from Myoporum species shows wide variations in optical purity.