Kibdelones: Novel Anticancer Polyketides from a Rare Australian Actinomycete

Ranjala Ratnayake, Ernest Lacey Dr., Shaun Tennant Dr., Jennifer H. Gill Dr., Robert J. Capon Prof.

Chemistry. (Weinheim an der Bergstrasse, Germany), 2006, 13, 1610-1619.

Publication Date: January 18, 2007


The kibdelones are a novel family of bioactive heterocyclic polyketides produced by a rare soil actinomycete, Kibdelosporangium sp. (MST-108465). Complete relative stereostructures were assigned to kibdelones A–C (13), kibdelone B rhamnoside (5), 13-oxokibdelone A (7), and 25-methoxy-24-oxokibdelone C (8) on the basis of detailed spectroscopic analysis and chemical interconversion, as well as mechanistic and biosynthetic considerations. Under mild conditions, kibdelones B (2) and C (3) undergo a facile equilibration to kibdelones A–C (13), while kibdelone B rhamnoside (5) equilibrates to a mixture of kibdelone A–C rhamnosides (46). A plausible mechanism for this equilibration is proposed and involves air oxidation, quinone/hydroquinone redox transformations, and a choreographed sequence of keto/enol tautomerizations that aromatize ring C via a quinone methide intermediate. Kibdelones exhibit potent and selective cytotoxicity against a panel of human tumor cell lines and display significant antibacterial and nematocidal activity.

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kibdelones A–C

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