36 (±)および(+)-Nootkatonesの合成

概要

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Synthetic strategies for the preparation of (±)- and (+)-nootkatones (1), the latter of which is known as an important odoriferous constituent of grapefruit, are described. A) (±)-1 was obtained by allylic oxidation of (±)-valencene (18), starting from 4β,10β-dimethyloctalone ethylene acetal 4 by stereocontrolled functionalizations involving the introduction of isopropenyl group at the C-6 position and the formation of double bond at the C-1(10) position leading to 18. B-1) Two different synthetic strategies discussed for the preparation of (+)-1 involve following ideas: one is elongation of carbon chain of keto ester 23 by the intramolecular alkylation of 28, reduction of the exo-methylene group of 36, and subsequent oxidative fission of the enolic olefin of 37 leading to acetonyl ketone 25, a key precursor of (+)-1; the other deals with the functionalization of tricyclo[7.1.1.0]undec-7-ene derivative 43 prepared from nopadiene and ethyl α-acetoxyacrylate by the Diels-Alder reaction by i) reductive methylation of epoxy ketone 46 to introduce the angular methyl group, ii) 1,4-addition of methyl group of dienone 50, and iii) isomerization of 4β-methyl group to 4α-isomer 55.
天然有機化合物討論会の論文
1981-09-10