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β-Triketone–Monoterpene Hybrids from the Flowers of the Australian Tree Corymbia intermedia

Senadeera, Sarath P. D., Robertson, Luke P., Duffy, Sandra, Wang, Yun, Avery, Vicky M., Carroll, Anthony R.
Journal of natural products 2018 v.81 no.11 pp. 2455-2461
Corymbia intermedia, Eucalyptus, Plasmodium falciparum, antiplasmodial properties, flowers, inhibitory concentration 50, moieties, monoterpenoids, nuclear magnetic resonance spectroscopy, trees
Four new β-triketone monoterpene hybrids, intermediones A–D (1–4), have been identified from the flowers of the Australian eucalypt tree Corymbia intermedia. Intermediones A–D are β-triketones that incorporate a pinene moiety attached via a benzyl group to a syncarpic acid. The structures of 1–4, including relative configurations, were elucidated from the analysis of 1D/2D NMR and MS data. The absolute configurations of intermediones A and B were determined by comparison of experimental and predicted ECD spectra. Intermedione D possesses a tetracyclic ring system that is related to that found in the meroterpenes, guadials B and C. Low to moderate antiplasmodial activity toward the chloroquine-sensitive (3D7) strain of Plasmodium falciparum, with IC₅₀ values ranging from 9.9 to 20.8 μM, was observed for intermediones A, B, and D.