The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Satoshi Minakata - One of the best experts on this subject based on the ideXlab platform.
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computational study on the mechanism and origin of the regioselectivity and Stereospecificity in pd sipr catalyzed ring opening cross coupling of 2 arylaziridines with arylboronic acids
ACS Catalysis, 2019Co-Authors: Akhilesh K Sharma, W M C Sameera, Youhei Takeda, Satoshi MinakataAbstract:The mechanism, regioselectivity, and Stereospecificity of Pd/NHC-catalyzed ring-opening cross-coupling of 2-arylaziridines with arylboronic acids (Takeda et al. J. Am. Chem. Soc. 2014, 136, 8544−8547) is rationalized from density functional theory calculations. Pd(0)SIPr complex, the active species, can be formed through the reduction of (η3-cinnamyl)(Cl)Pd(II)SIPr complex, where arylboronic acid in solution plays a key role. Then the Pd(0)SIPr complex acts as the active species of the catalytic cycle that consists of the regioselective and stereospecific oxidative addition, proton transfer, rate-determining transmetalation, and reductive elimination. Transition states for the oxidative addition were systematically determined from a multicomponent artificial force induced reaction search and explained the regioselectivity and Stereospecificity of the reaction. An energy decomposition analysis on the key transition states suggested that the interactions between Pd(0)SIPr and 2-arylaziridines are important ...
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Computational Study on the Mechanism and Origin of the Regioselectivity and Stereospecificity in Pd/SIPr-Catalyzed Ring-Opening Cross-Coupling of 2‑Arylaziridines with Arylboronic Acids
2019Co-Authors: Akhilesh K. Sharma, W M C Sameera, Youhei Takeda, Satoshi MinakataAbstract:The mechanism, regioselectivity, and Stereospecificity of Pd/NHC-catalyzed ring-opening cross-coupling of 2-arylaziridines with arylboronic acids (Takeda et al. J. Am. Chem. Soc. 2014, 136, 8544−8547) is rationalized from density functional theory calculations. Pd(0)SIPr complex, the active species, can be formed through the reduction of (η3-cinnamyl)(Cl)Pd(II)SIPr complex, where arylboronic acid in solution plays a key role. Then the Pd(0)SIPr complex acts as the active species of the catalytic cycle that consists of the regioselective and stereospecific oxidative addition, proton transfer, rate-determining transmetalation, and reductive elimination. Transition states for the oxidative addition were systematically determined from a multicomponent artificial force induced reaction search and explained the regioselectivity and Stereospecificity of the reaction. An energy decomposition analysis on the key transition states suggested that the interactions between Pd(0)SIPr and 2-arylaziridines are important to the selectivity. The computed mechanism of the full catalytic cycle is consistent with the experimental data. Our detailed mechanistic survey provides important mechanistic insights for enantiospecific and regioselective ring-opening reactions of 2-arylaziridines
Haruka Ozaki - One of the best experts on this subject based on the ideXlab platform.
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reaction pathway of tryptophanase catalyzed l tryptophan synthesis from d serine
Journal of Chromatography B, 2011Co-Authors: Haruka Ozaki, Takeshi Saito, Noriko FujiiAbstract:Abstract Tryptophanase, l -tryptophan indole-lyase with extremely absolute Stereospecificity, can change the Stereospecificity in concentrated diammonium hydrogenphosphate solution. While tryptophanase is not inert to d -serine in the absence of diammonium hydrogenphosphate, it can undergo l -tryptophan synthesis from d -serine along with indole in the presence of it. It has been well known that tryptophanase synthesizes l -tryptophan from l -serine through a β-substitution mechanism of the ping-pong type. However, a metabolic pathway of l -tryptophan synthesis from d -serine has remained unclear. The present study aims to elucidate it. Diammonium hydrogenphosphate plays a role in the emergence of catalytic activity on d -serine. The salt gives tryptophanase a small conformational change, which makes it possible to catalyze d -serine. Tryptophanase-bound d -serine produces l -tryptophan synthesis by β-replacement reaction via the enzyme-bound aminoacrylate intermediate. Our result will be valuable in studying the origin of homochirality.
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tryptophanase catalyzed l tryptophan synthesis from d serine in the presence of diammonium hydrogen phosphate
International Journal of Molecular Sciences, 2009Co-Authors: A Shimada, Haruka Ozaki, Takeshi Saito, Fujii NorikoAbstract:Tryptophanase, an enzyme with extreme absolute Stereospecificity for optically active stereoisomers, catalyzes the synthesis of L-tryptophan from L-serine and indole through a β-substitution mechanism of the ping-pong type, and has no activity on D-serine. We previously reported that tryptophanase changed its Stereospecificity to degrade D- tryptophan in highly concentrated diammonium hydrogen phosphate, (NH4)2HPO4 solution. The present study provided the same stereospecific change seen in the D- tryptophan degradation reaction also occurs in tryptophan synthesis from D-serine. Tryptophanase became active to D-serine to synthesize L-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. D-serine seems to undergo β-replacement via an enzyme-bonded α-aminoacylate intermediate to yield L-tryptophan.
Noriko Fujii - One of the best experts on this subject based on the ideXlab platform.
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reaction pathway of tryptophanase catalyzed l tryptophan synthesis from d serine
Journal of Chromatography B, 2011Co-Authors: Haruka Ozaki, Takeshi Saito, Noriko FujiiAbstract:Abstract Tryptophanase, l -tryptophan indole-lyase with extremely absolute Stereospecificity, can change the Stereospecificity in concentrated diammonium hydrogenphosphate solution. While tryptophanase is not inert to d -serine in the absence of diammonium hydrogenphosphate, it can undergo l -tryptophan synthesis from d -serine along with indole in the presence of it. It has been well known that tryptophanase synthesizes l -tryptophan from l -serine through a β-substitution mechanism of the ping-pong type. However, a metabolic pathway of l -tryptophan synthesis from d -serine has remained unclear. The present study aims to elucidate it. Diammonium hydrogenphosphate plays a role in the emergence of catalytic activity on d -serine. The salt gives tryptophanase a small conformational change, which makes it possible to catalyze d -serine. Tryptophanase-bound d -serine produces l -tryptophan synthesis by β-replacement reaction via the enzyme-bound aminoacrylate intermediate. Our result will be valuable in studying the origin of homochirality.
Takeshi Saito - One of the best experts on this subject based on the ideXlab platform.
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reaction pathway of tryptophanase catalyzed l tryptophan synthesis from d serine
Journal of Chromatography B, 2011Co-Authors: Haruka Ozaki, Takeshi Saito, Noriko FujiiAbstract:Abstract Tryptophanase, l -tryptophan indole-lyase with extremely absolute Stereospecificity, can change the Stereospecificity in concentrated diammonium hydrogenphosphate solution. While tryptophanase is not inert to d -serine in the absence of diammonium hydrogenphosphate, it can undergo l -tryptophan synthesis from d -serine along with indole in the presence of it. It has been well known that tryptophanase synthesizes l -tryptophan from l -serine through a β-substitution mechanism of the ping-pong type. However, a metabolic pathway of l -tryptophan synthesis from d -serine has remained unclear. The present study aims to elucidate it. Diammonium hydrogenphosphate plays a role in the emergence of catalytic activity on d -serine. The salt gives tryptophanase a small conformational change, which makes it possible to catalyze d -serine. Tryptophanase-bound d -serine produces l -tryptophan synthesis by β-replacement reaction via the enzyme-bound aminoacrylate intermediate. Our result will be valuable in studying the origin of homochirality.
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tryptophanase catalyzed l tryptophan synthesis from d serine in the presence of diammonium hydrogen phosphate
International Journal of Molecular Sciences, 2009Co-Authors: A Shimada, Haruka Ozaki, Takeshi Saito, Fujii NorikoAbstract:Tryptophanase, an enzyme with extreme absolute Stereospecificity for optically active stereoisomers, catalyzes the synthesis of L-tryptophan from L-serine and indole through a β-substitution mechanism of the ping-pong type, and has no activity on D-serine. We previously reported that tryptophanase changed its Stereospecificity to degrade D- tryptophan in highly concentrated diammonium hydrogen phosphate, (NH4)2HPO4 solution. The present study provided the same stereospecific change seen in the D- tryptophan degradation reaction also occurs in tryptophan synthesis from D-serine. Tryptophanase became active to D-serine to synthesize L-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. D-serine seems to undergo β-replacement via an enzyme-bonded α-aminoacylate intermediate to yield L-tryptophan.
Fujii Noriko - One of the best experts on this subject based on the ideXlab platform.
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tryptophanase catalyzed l tryptophan synthesis from d serine in the presence of diammonium hydrogen phosphate
International Journal of Molecular Sciences, 2009Co-Authors: A Shimada, Haruka Ozaki, Takeshi Saito, Fujii NorikoAbstract:Tryptophanase, an enzyme with extreme absolute Stereospecificity for optically active stereoisomers, catalyzes the synthesis of L-tryptophan from L-serine and indole through a β-substitution mechanism of the ping-pong type, and has no activity on D-serine. We previously reported that tryptophanase changed its Stereospecificity to degrade D- tryptophan in highly concentrated diammonium hydrogen phosphate, (NH4)2HPO4 solution. The present study provided the same stereospecific change seen in the D- tryptophan degradation reaction also occurs in tryptophan synthesis from D-serine. Tryptophanase became active to D-serine to synthesize L-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. D-serine seems to undergo β-replacement via an enzyme-bonded α-aminoacylate intermediate to yield L-tryptophan.
