18 GENERAL SYNTHETIC METHOD FOR MACROCYCLIC KETONES BY INTRAMOLECULAR ALKYLATION OF PROTECTED CYANOHYDRIN, AND ITS APPLICATION TO THE SYNTHESES OF MUSCONE, EXALTONE, ZEARALENONE, AND RESORCILIDE
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We report here a simple synthetic method for macrocyclic ketones based on intramolecular alkylation of carbanion, generated from protected cyanohydrin. Subsequent mild treatment with acid and base of the cyclized products leads to macrocyclic ketones in high yields. The present method of alkylation can generate mono-carbanion easily and the reaction is rapid and irreversible, and hence requires short reaction time. This method was successfully applied to the synthesis of trans-2-cyclopentadecenenone 15 as a precursor of (±)-Muscone and Exaltone. As synthetic targets of keto lactones, we synthesized the naturally occurring Zearalenone and trans-Resorcilide. Zearalenone was also prepared in high yield by intramolecular alkylation of dianione of the ester 33.
