- Highly enantioselective synthesis of 2,6-disubstituted and 2,2,6-trisubstituted dihydropyrones: A one-step synthesis of (R)-(+)-hepialone and its analogues
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An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels-Alder (HDA) reactions of (E)-4-methoxy-2- trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4 (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched β-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity.
- Yang, Weiqing,Shang, Deju,Liu, Yanling,Du, Ying,Feng, Xiaoming
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p. 8533 - 8537
(2007/10/03)
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- On the Scope of Asymmetric Nitrile Oxide Cycloadditions with Oppolzer's Chiral Sultam. Total Syntheses of (+)-Hepialone, (-)-(1R,3R,5S)-1,3-Dimethyl-2,9-dioxabicyclooctane
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Cycloadditions of nitrile oxides with acryloyl derivatives of Oppolzer's chiral sultam produce stereoisomeric Δ2-isoxazolines in ratios of about 90/10 at 25 deg C.The major diastereomers can be isolated in pure form in 70-88percent yield.Synthe
- Curran, Dennis P.,Heffner, Timothy A.
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p. 4585 - 4595
(2007/10/02)
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- SYNTHESIS OF HEPIALONE; PRINCIPAL COMPONENT FROM MALE SEX SCALES OF HEPIALUS CALIFORNICUS (LEPIDOPTERA)
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Racemic and optically active hepialone, a new sex-pheromonal component produced by the male moth, Hepialus californicus Bvd., was synthesized and thus confirmed the structure of the pheromone as (2R)-2,3-dihydro-2-ethyl-6-methyl-4H-pyran-4-one (1).
- Uchino, Keiso,Yamagiwa, Yoshiro,Kamikawa, Tadao,Kubo, Isao
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p. 1319 - 1320
(2007/10/02)
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