- 1,2(3)-TETRAHYDRO-3,3'-BIPLUMBAGIN: A NAPHTHALENONE AND OTHER CONSTITUENTS FROM PLUMBAGO ZEYLANICA
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The isolation of plumbagin, droserone, isoshinanolone and a new naphthalenone, 1,2(3)-tetrahydro-3,3'-biplumbagin is reported from the phenolic fraction of the lightpetrol extract of the roots of Plumbago zeylanica.The structure of the new naphthalenone was elucidated by means of spectroscopic data and chemical interconversions.The main constituent of the neutral fraction was shown to be sitosterol. - Key Words: Plumbago zeylanica; Plumbaginaceae; plumbagin; droserone; isoshinanolone; naphthalenones; 1,2(3)-tetrahydro-3,3'-biplumbagin; sitosterol; structure elucidation.
- Gunaherath, G.M.Kamal B.,Gunatilaka, A.A.Leslie,Sultanbawa, M. Uvais S.,Balasubramaniam, S.
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- The aryl-aryl coupling reaction of 1-naphthol with SnCl4 for 2,2′-binaphthol synthesis and its application to the biomimetic synthesis of binaphthoquinone isolated from Plumbago zeylanica
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A simple method for the direct synthesis of 2,2′-binaphthols was developed, utilizing aryl-aryl coupling reaction via electron donor-acceptor complexes of 1-naphthols with SnCl4. Heating of the complex in a sealed tube afforded the corresponding o-o coupling product in excellent yield. This method was utilized for a biomimetic synthesis of the binaphthoquinone, 3,3′-biplumbagin, isolated from Plumbago zeylanica.
- Okamoto, Iwao,Doi, Hirohisa,Kotani, Eiichi,Takeya, Tetsuya
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- Three different dimerizations of 2-bromo-3-methyl-1,4-naphthoquinones
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Three types of dimeric naphthoquinones, which possess structurally diverse skeletons, can be prepared in one step from 2-bromo-3-methyl-1,4- naphthoquinones. 2,2′-Dimeric naphthoquinones were prepared by a one-pot Stille-type reaction via vinylstannanes. Oxepines are formed by unexpected domino reactions via 1,4-dihydroxynaphthalene species. Epoxides are formed by a Michael/Darzens reaction via the o-quinone methides.
- Azuma, Shuhei,Nishio, Kazuyuki,Kubo, Konomi,Sasamori, Takahiro,Tokitoh, Norihiro,Kuramochi, Kouji,Tsubaki, Kazunori
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- Oxidative coupling of methoxynaphthylenediols
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The oxidative coupling of a mixture of 1-methoxy-7-methyl-4,5- naphthylenediol and 4-methoxy-7-methyl-1,5-naphthylenediol using lead(IV) oxide gives the symmetrical bisnaphthalene indigos diosindigo A and diosindigo B together with the corresponding unsymmetrical isomer. Oxidation of the first two by nitric acid gives the binaphthyldiquinones mamegakinone and biramentaceone, respectively; the third gives the unsymmetrical diquinone rotundiquinone. Similar oxidations of related naphthylenediols are described.
- Maiti, Bhim C.,Musgrave, Oliver C.,Skoyles, Douglas
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p. 6568 - 6574
(2007/10/03)
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- Aerobic oxidative dimerization of 1-naphthols to 2,2′- binaphthoquinones mediated by SnCl4 and its application to natural product synthesis
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We developed a simple method for the direct synthesis of 2,2′-binaphthoquinones, utilizing oxidative dimerization via electron donor-acceptor complex formation of 1-naphthols with SnCl4 in the presence of dioxygen. This oxidation involves a catalytic cycle of SnCl 4, and the reaction mechanism is discussed. As an application of this method to natural products synthesis, we describe facile biomimetic syntheses of the binaphthoquinones 3,3′-bijuglone, 3,3′-biplumbagin and elliptinone.
- Takeya, Tetsuya,Doi, Hirohisa,Ogata, Tokutaro,Okamoto, Iwao,Kotani, Eiichi
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p. 9049 - 9060
(2007/10/03)
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- SnCl4-mediated oxidative reaction for formation of binaphthoquinone and dinaphthofuran frameworks and its application to natural product synthesis
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A simple method was developed for the direct synthesis of 2,2′-binaphthoquinones and dinaphtho[1,2-b;2′,1′-d]furans, utilizing an oxidative reaction via electron donor-acceptor complexes of 1-naphthols with SnCl4 in the absence or presence of dioxygen. As an application of this method to natural product synthesis, we describe a facile biomimetic synthesis of several binaphthoquinones, 3,3′-bijuglone, 3,3′-biplumbagin and elliptinone.
- Ogata, Tokutaro,Okamoto, Iwao,Doi, Hirohisa,Kotani, Eiichi,Takeya, Tetsuya
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p. 2041 - 2044
(2007/10/03)
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- Dimeric Naphthoquinones, XIX.- Ammonium Cerium(IV) Nitrate as Oxidising Agent: Synthesis of Dimeric Naphthazarins
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Dimeric 1-naphthols (type 8 or 10) are easily oxidised using ammonium cerium(IV) nitrate, yielding the quinones of type 9 or 11.By dealkylation of the latter, several potentially naturally occuring binaphthazarin derivatives and the natural products 8'-hy
- Laatsch, Hartmut
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p. 1669 - 1686
(2007/10/02)
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