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Issue 4, 2005
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The first total synthesis of kwakhurin, a characteristic component of a rejuvenating plant, “kwao keur”: toward an efficient synthetic route to phytoestrogenic isoflavones

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Abstract

A convergent synthesis of kwakhurin (5), a characteristic estrogen-like isoflavone of Pueraria mirifica (Leguminosae), is described. Isoflavone skeleton 31 was constructed by Suzuki–Miyaura coupling of 3-bromochromone 26 (AC-ring) and arylboronic acid 30 (B-ring) in the presence of TBAB as an additive. Microwave-assisted coupling was also examined, but did not improve the yield. Baeyer–Villiger oxidation, followed by propargylation and reduction afforded 1,1-dimethylallyl ether 37. 6′-Prenylisoflavone 34 was obtained in high yield by Claisen rearrangement of 37 in N,N-diethylaniline. On the other hand, 1,3-rearrangement of prenyl ether 33 with clay gave 34 in poor yield. Successive methylation of 34 and deprotection yielded the target kwakhurin (5) in 12% overall yield from 2,4-dihydroxybenzaldehyde (23).

Graphical abstract: The first total synthesis of kwakhurin, a characteristic component of a rejuvenating plant, “kwao keur”: toward an efficient synthetic route to phytoestrogenic isoflavones

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Publication details

The article was received on 27 Sep 2004, accepted on 09 Dec 2004 and first published on 24 Jan 2005


Article type: Paper
DOI: 10.1039/B414955F
Citation: Org. Biomol. Chem., 2005,3, 674-681
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    The first total synthesis of kwakhurin, a characteristic component of a rejuvenating plant, “kwao keur”: toward an efficient synthetic route to phytoestrogenic isoflavones

    F. Ito, M. Iwasaki, T. Watanabe, T. Ishikawa and Y. Higuchi, Org. Biomol. Chem., 2005, 3, 674
    DOI: 10.1039/B414955F

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