Biomimetic synthesis of neodihydrothebaine and bractazonine from thebaine

Theuns, Hubert G.; Vos, Guus F. La; Brauw, M.C. ten Noever de; Salemink, C. A.

doi:10.1016/s0040-4039(01)90210-2

Cited by 8 publications

(5 citation statements)

References 7 publications

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“…Thus, we propose that treatment of 5 with L-Selectride is causing rearrangement as shown in Scheme . (+)-Bractazonine ( 7 ) has been prepared previously from 1 , , but only in very low yield by treatment with UV irradiation. We considered that this product could only be formed via a migration of the phenyl group of 5 to the 14-position (Figure ) with the lithium ion of L-Selectride acting as the Lewis acid, followed by reduction of the iminium ion to give 8 .…”

Section: Resultsmentioning

confidence: 99%

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Rearrangement of 5-Trimethylsilylthebaine on Treatment with L-Selectride: An Efficient Synthesis of (+)-Bractazonine

Chen

Bernard

et al. 2003

J. Org. Chem.

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Treatment of 5-trimethylsilylthebaine with L-Selectride gave rise to a rearrangement to 10-trimethylsilylbractazonine through migration of the phenyl group, whereas treatment of thebaine with strong Lewis acids is known to lead to a similar rearrangement through migration of the alkyl bridge to give, after reduction, (+)-neodihydrothebaine. It is suggested that the rearrangement of the alkyl group of thebaine is favored due to the formation of a tertiary benzylic cation. However, for 5-trimethylsilylthebaine, the lithium ion of L-Selectride acts as the Lewis acid and the beta-silyl effect dominates in the stabilization of any positive charge. This rearrangement provides a clear example of the greater relative migratory aptitude of phenyl groups over alkyl groups, and provides an efficient synthesis of (+)-bractazonine from thebaine.

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Section: Resultsmentioning

confidence: 99%

“…(+)-Bractazonine (7). , To a stirred solution of 8 (0.19 g, 0.5 mmol) in CH 2 Cl 2 (10 mL) was added TFA (1 mL) at room temperature, and the mixture was stirred overnight. The reaction mixture was concentrated, and the residue was taken into CHCl 3 (50 mL), washed with NaHCO 3 , water, and brine, dried (Na 2 SO 4 ), and concentrated.…”

Section: Methodsmentioning

confidence: 99%

Rearrangement of 5-Trimethylsilylthebaine on Treatment with L-Selectride: An Efficient Synthesis of (+)-Bractazonine

Chen

Bernard

et al. 2003

J. Org. Chem.

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“…[223] Ebenfalls biomimetisch verlief die photoinduzierte Gerüstumla-gerung von (À)-Thebain zu Neodihydrothebain und Bractazonin unter basischen Bedingungen. [224] 6. Reaktionen über Dienol-Zwischenstufen…”

Section: Umlagerungen Von Kreuzkonjugierten Cyclohexadienonenunclassified

Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese

2011

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Photochemische Reaktionen bereichern in signifikanter Weise das Repertoire zur Knüpfung von Kohlenstoff‐Kohlenstoff‐Bindungen und machen ungewöhnliche, auf herkömmlichem Weg nicht erhältliche Molekülgerüste zugänglich. In diesem Aufsatz werden die wichtigsten Umsetzungen der Photochemie vorgestellt, die auf breiter Front Einzug in die Naturstoffsynthese gehalten haben. Beispielhaft werden einzelne Totalsynthesen diskutiert, wobei besonderes Augenmerk auf den photochemischen Schlüsselschritt sowie dessen Stereoselektivität gerichtet ist. Dabei wird das photochemisch erzeugte Molekül in Relation zur Struktur des Naturstoffs gebracht, und Folgereaktionen werden, wo notwendig, illustriert und klassifiziert.

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“…A quinone served as the chromophore for the photochemical isomerization of (+)‐komaroviquinone to (+)‐komarovispirone, a reaction that is though to be part of the biosynthetic pathway 223. In another biomimetic reaction, the photoinduced skeletal rearrangement of (−)‐thebaine proceeded under basic conditions to afford neodihydrothebaine and bractazonine 224…”

Section: Photochemical Rearrangementsmentioning

confidence: 99%

Corrosion News

2007

Materials & Corrosion

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Photochemical reactions contribute in a significant way to the existing repertoire of carbon–carbon bond‐forming reactions by allowing access to exceptional molecular structures that cannot be obtained by conventional means. In this Review, the most important photochemical transformations that have been employed in natural product synthesis are presented. Selected total syntheses are discussed as examples, with particular attention given to the photochemical key step and its stereoselectivity. The structural relationship between the photochemically generated molecule and the natural product is shown, and, where necessary, the consecutive reactions in the synthesis are illustrated and classified.

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Biomimetic synthesis of neodihydrothebaine and bractazonine from thebaine

Abstract: Abstract:Photochemical irradiation of the morphinan alkaloid thebaine l_, followed by reduction, affords the dibenz[d,f]azonine alkaloids neodihydrothebaine 2 and bractazonine 3, in a sequence paralleling the proposed biosynthesis of these alkaloids in Papaver bracteatum.

Cited by 8 publications

References 7 publications

Rearrangement of 5-Trimethylsilylthebaine on Treatment with L-Selectride: An Efficient Synthesis of (+)-Bractazonine

Rearrangement of 5-Trimethylsilylthebaine on Treatment with L-Selectride: An Efficient Synthesis of (+)-Bractazonine

Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese

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