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Lukasz Bogdan - One of the best experts on this subject based on the ideXlab platform.
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Interplay of Nitrogen-Atom Inversion and Conformational Inversion in Enantiomerization of 1H-1-Benzazepines.
The Journal of organic chemistry, 2016Co-Authors: Keith Ramig, Gopal Subramaniam, Sasan Karimi, David J. Szalda, Aaron Lam, Ani Coaderaj, Leyla Cavdar, Lukasz BogdanAbstract:A series of 2,4-disubstituted 1H-1-benzazepines, 2a–d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The Conformational Inversion (ring-flip) and nitrogen-atom Inversion (N-Inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-Inversion. When the nitrogen-atom substituent was alkyl, as in 2a–c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-Inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high ...
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Interplay of Nitrogen-Atom Inversion and Conformational Inversion in Enantiomerization of 1H‑1-Benzazepines
2016Co-Authors: Keith Ramig, Gopal Subramaniam, Sasan Karimi, David J. Szalda, Aaron Lam, Ani Coaderaj, Leyla Cavdar, Lukasz BogdanAbstract:A series of 2,4-disubstituted 1H-1-benzazepines, 2a–d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The Conformational Inversion (ring-flip) and nitrogen-atom Inversion (N-Inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-Inversion. When the nitrogen-atom substituent was alkyl, as in 2a–c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-Inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high energy barrier to N-Inversion and a low barrier to ring-flip. In these N-unsubstituted compounds, it was found computationally that the lowest-energy stereodynamic process was ring-flip coupled with N-Inversion, as N-Inversion alone had a much higher energy barrier
Michel Frederich - One of the best experts on this subject based on the ideXlab platform.
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dimeric bisindole alkaloids from the stem bark of strychnos nux vomica l
Phytochemistry, 2013Co-Authors: Mariecaroline Jonville, Joanne Bero, Monique Tits, Luc Angenot, Georges Dive, Evelyne Ollivier, Michel FrederichAbstract:Strychnos nux-vomica L. (Loganiaceae) is famous for its monomeric alkaloid content, such as strychnine, a convulsant poison. The stem bark of the tree is traditionally used to treat intermittent fever in South East Asia. In various studies, it appeared that dimeric indolo-monoterpenic alkaloids possess a promising activity on Plasmodium falciparum. Three bisindolomonoterpenic alkaloids together with strychnochrysine, previously identified in the root bark of S. nux-vomica, were isolated from the stem bark. The structures of these compounds were established using NMR spectroscopy and mass spectrometry. Stereochemistry of the compounds was confirmed by molecular modelling. This then allowed the structural determination of strychnoflavine, a coloured bisindole alkaloid previously isolated from the root bark of the tree. Moreover, the Conformational Inversion in alkaloids possessing an ether bond in the strychnane moiety could be easily predicted by specific δ 13 C NMR values. These longicaudatine-type alkaloids were found to display in vitro antiplasmodial activity against a chloroquine resistant strain and a chloroquine sensitive strain. The most interesting was strychnochrysine showing an IC 50 value at around 10 μM. © 2012 Elsevier Ltd. All rights reserved.
Keith Ramig - One of the best experts on this subject based on the ideXlab platform.
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Interplay of Nitrogen-Atom Inversion and Conformational Inversion in Enantiomerization of 1H-1-Benzazepines.
The Journal of organic chemistry, 2016Co-Authors: Keith Ramig, Gopal Subramaniam, Sasan Karimi, David J. Szalda, Aaron Lam, Ani Coaderaj, Leyla Cavdar, Lukasz BogdanAbstract:A series of 2,4-disubstituted 1H-1-benzazepines, 2a–d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The Conformational Inversion (ring-flip) and nitrogen-atom Inversion (N-Inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-Inversion. When the nitrogen-atom substituent was alkyl, as in 2a–c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-Inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high ...
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Interplay of Nitrogen-Atom Inversion and Conformational Inversion in Enantiomerization of 1H‑1-Benzazepines
2016Co-Authors: Keith Ramig, Gopal Subramaniam, Sasan Karimi, David J. Szalda, Aaron Lam, Ani Coaderaj, Leyla Cavdar, Lukasz BogdanAbstract:A series of 2,4-disubstituted 1H-1-benzazepines, 2a–d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The Conformational Inversion (ring-flip) and nitrogen-atom Inversion (N-Inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-Inversion. When the nitrogen-atom substituent was alkyl, as in 2a–c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-Inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high energy barrier to N-Inversion and a low barrier to ring-flip. In these N-unsubstituted compounds, it was found computationally that the lowest-energy stereodynamic process was ring-flip coupled with N-Inversion, as N-Inversion alone had a much higher energy barrier
Mariecaroline Jonville - One of the best experts on this subject based on the ideXlab platform.
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dimeric bisindole alkaloids from the stem bark of strychnos nux vomica l
Phytochemistry, 2013Co-Authors: Mariecaroline Jonville, Joanne Bero, Monique Tits, Luc Angenot, Georges Dive, Evelyne Ollivier, Michel FrederichAbstract:Strychnos nux-vomica L. (Loganiaceae) is famous for its monomeric alkaloid content, such as strychnine, a convulsant poison. The stem bark of the tree is traditionally used to treat intermittent fever in South East Asia. In various studies, it appeared that dimeric indolo-monoterpenic alkaloids possess a promising activity on Plasmodium falciparum. Three bisindolomonoterpenic alkaloids together with strychnochrysine, previously identified in the root bark of S. nux-vomica, were isolated from the stem bark. The structures of these compounds were established using NMR spectroscopy and mass spectrometry. Stereochemistry of the compounds was confirmed by molecular modelling. This then allowed the structural determination of strychnoflavine, a coloured bisindole alkaloid previously isolated from the root bark of the tree. Moreover, the Conformational Inversion in alkaloids possessing an ether bond in the strychnane moiety could be easily predicted by specific δ 13 C NMR values. These longicaudatine-type alkaloids were found to display in vitro antiplasmodial activity against a chloroquine resistant strain and a chloroquine sensitive strain. The most interesting was strychnochrysine showing an IC 50 value at around 10 μM. © 2012 Elsevier Ltd. All rights reserved.
Gopal Subramaniam - One of the best experts on this subject based on the ideXlab platform.
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Interplay of Nitrogen-Atom Inversion and Conformational Inversion in Enantiomerization of 1H-1-Benzazepines.
The Journal of organic chemistry, 2016Co-Authors: Keith Ramig, Gopal Subramaniam, Sasan Karimi, David J. Szalda, Aaron Lam, Ani Coaderaj, Leyla Cavdar, Lukasz BogdanAbstract:A series of 2,4-disubstituted 1H-1-benzazepines, 2a–d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The Conformational Inversion (ring-flip) and nitrogen-atom Inversion (N-Inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-Inversion. When the nitrogen-atom substituent was alkyl, as in 2a–c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-Inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high ...
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Interplay of Nitrogen-Atom Inversion and Conformational Inversion in Enantiomerization of 1H‑1-Benzazepines
2016Co-Authors: Keith Ramig, Gopal Subramaniam, Sasan Karimi, David J. Szalda, Aaron Lam, Ani Coaderaj, Leyla Cavdar, Lukasz BogdanAbstract:A series of 2,4-disubstituted 1H-1-benzazepines, 2a–d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The Conformational Inversion (ring-flip) and nitrogen-atom Inversion (N-Inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-Inversion. When the nitrogen-atom substituent was alkyl, as in 2a–c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-Inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high energy barrier to N-Inversion and a low barrier to ring-flip. In these N-unsubstituted compounds, it was found computationally that the lowest-energy stereodynamic process was ring-flip coupled with N-Inversion, as N-Inversion alone had a much higher energy barrier