Tuning Diketodioxinone Reactivity: Biomimetic Synthesis of the Resorcylate Antibiotic Fungal Metabolitesent-W1278A, -B, and -C, Using Iterative Aromatization Reactions
Ismael Navarro,† Christoph P€verlein,† Gerhard Schlingmann,‡ and o Anthony G.M. Barrett*,†
Department of Chemistry, Imperial College, London SW7 2AZ, England, and ‡Wyeth Research, Natural ProductsDiscovery, Middletown Road, Pearl River, New York 10965 email@example.com Received July 22, 2009
The onset temperature of theretro-Diels-Alder reactions of diketo-1,3-dioxin-2-ones to generate R,γ,ε-triketo-ketenes was found to be significantly reduced with2-phenyl substitution. These ketenes, generated at 78 °C, were trapped with alcohols to provide resorcylate esters following aromatizationby sequential reaction with cesium acetate and trifluoroacetic acid. The methodology was applied iteratively to the total synthesisof the resorcylate antibiotics W1278A, -B, and -C. It is noteworthy that in this process the linking of the monomer units occurs duringconstruction of the aromatic ring.
Introduction A distinguishing feature of numerous bioactive natural products is the6-alkyl-2,4-dihydroxybenzoic acid unit.1 This unit also serves as the backbone of the oligo-esters W1278A (1a, n = 2), -B (1b, n = 3), and -C [continua]
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