The Experts below are selected from a list of 3762 Experts worldwide ranked by ideXlab platform
Zhuo Zheng - One of the best experts on this subject based on the ideXlab platform.
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new chiral amino alcohol ligands derived from 1 phenylethylamine for efficient ru catalyzed asymmetric transfer hydrogenation
2011Co-Authors: Meiling Han, Jiadi Huang, Ligong Chen, Zhuo ZhengAbstract:A series of chiral amino alcohols have been prepared from cheap and readily available (S)-1-Phenylethylamine through a one-step transformation. The ability of these newly developed amino alcohols as chiral ligands was evaluated in the Ru-catalyzed asymmetric transfer hydrogenation of aromatic alkyl ketones, providing chiral secondary alcohols with good to excellent conversions (71–100%) and moderate to good enantioselectivities (67–95% ee). The results also showed that the structure of these amino alcohols has a significant influence on the conversion and enantioselectivity.
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readily available chiral phosphine aminophosphine ligands derived from 1 phenylethylamine for rh catalyzed enantioselective hydrogenations
2010Co-Authors: Xiaomao Zhou, Jiadi Huang, Libin Luo, Chenglu Zhang, Zhuo ZhengAbstract:Among the novel phosphineaminophosphine derivatives prepared, effective ligands are identified for the Rh-catalyzed asymmetric hydrogenation of enamides (II), Z-β-dehydroamino acid esters (VI), and itaconate (IX).
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chiral 1 phenylethylamine derived phosphine phosphoramidite ligands for highly enantioselective rh catalyzed hydrogenation of β acylamino acrylates significant effect of substituents on 3 3 positions of binaphthyl moiety
2010Co-Authors: Xiaomao Zhou, Jiadi Huang, Libin Luo, Chenlu Zhang, Zhuo ZhengAbstract:A series of new chiral phosphine-phosphoramidite ligands with a 3,3′-substituted binaphthyl moiety were prepared from 1-Phenylethylamine, and successfully applied in the Rh-catalyzed asymmetric hydrogenation of β-(acylamino)acrylates. The research disclosed that the substituents on the 3,3′-positions of binaphthyl moiety significantly influenced the enantioselectivity.
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synthesis of novel chiral phosphine triazine ligand derived from α phenylethylamine for pd catalyzed asymmetric allylic alkylation
2008Co-Authors: Jia Di Huang, Zhuo ZhengAbstract:Abstract A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1,3-diphenylprop-2-en-1-yl pivalate with dimethyl malonate, good enantioselectivity (90% e.e.) was obtained by using this ligand.
V Popov - One of the best experts on this subject based on the ideXlab platform.
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effects of ph and temperature on s amine activity of transaminase from the cold adapted bacterium psychrobacter cryohalolentis
2020Co-Authors: Ekaterina Yu Bezsudnova, T N Stekhanova, Aleksandr O Ruzhitskiy, V PopovAbstract:(7R,8S)-diaminopelargonic acid transaminase from the cold-adapted Gram-negative bacterium Psychrobacter cryohalolentis (Pcryo361) is able to react with unnatural substrates including (S)-( +)-1-Phenylethylamine, aldehydes and α-diketones. Additionally, Pcryo361 is active at 0-50 °C and retains up to 10% of the maximum activity at 0 °C. Here, we report a detailed study on the stability and low temperature activity of Pcryo361. At the optimal pH for (S)-amine activity (pH 10.0), the enzyme was stable at 0-10 °C and no decrease in the enzyme activity was observed within 24 h in a slightly alkaline medium, pH 8.0, at 35 °C. Pcryo361 was solvent stable and was activated in 10% DMSO and DMFA at 35 °C. An analysis of the efficiency of catalysis of Pcryo361 at 35 °C and 10 °C showed that the specificity towards (S)-( +)-1-Phenylethylamine dropped at 10 °C; however, the specificity towards 2,3-butanedione remained unchanged. Inhibition analysis showed that Pcryo361 activity was not inhibited by acetophenone but inhibited by amines (products of aldehyde amination). The observed pH stability and low temperature activity of Pcryo361 with activated keto substrates are attractive features in the field of development of stereoselective amination at low temperatures.
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diaminopelargonic acid transaminase from psychrobacter cryohalolentis is active towards s 1 phenylethylamine aldehydes and alpha diketones
2018Co-Authors: Ekaterina Yu Bezsudnova, T N Stekhanova, A V Popinako, T V Rakitina, Alena Yu Nikolaeva, Konstantin M Boyko, V PopovAbstract:Substrate and reaction promiscuity is a remarkable property of some enzymes and facilitates the adaptation to new metabolic demands in the evolutionary process. Substrate promiscuity is also a basis for protein engineering for biocatalysis. However, molecular principles of enzyme promiscuity are not well understood. Even for the widely studied PLP-dependent transaminases of class III, the reliable prediction of the biocatalytically important amine transaminase activity is still difficult if the desired activity is unrelated to the natural activity. Here, we show that 7,8-diaminopelargonic acid transaminase (synthase), previously considered to be highly specific, is able to convert (S)-(-)-1-Phenylethylamine and a number of aldehydes and diketones. We were able to characterize the (S)-amine transaminase activity of 7,8-diaminopelargonic acid transaminase from Psychrobacter cryohalolentis (Pcryo361) and analyzed the three-dimensional structure of the enzyme. New substrate specificity for α-diketones was observed, though only a weak activity towards pyruvate was found. We examined the organization of the active site and binding modes of S-adenosyl-L-methionine and (S)-(-)-1-Phenylethylamine using X-ray analysis and molecular docking. We suggest that the Pcryo361 affinity towards (S)-(-)-1-Phenylethylamine arises from the recognition of the hydrophobic parts of the specific substrates, S-adenosyl-L-methionine and 7-keto-8-aminopelargonic acid, and from the flexibility of the active site. Our results support the observation that the conversion of amines is a promiscuous activity of many transaminases of class III and is independent from their natural function. The analysis of amine transaminase activity from among various transaminases will help to make the sequence-function prediction for biocatalysis more reliable.
Magnus Carlquist - One of the best experts on this subject based on the ideXlab platform.
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improvement of whole cell transamination with saccharomyces cerevisiae using metabolic engineering and cell pre adaptation
2017Co-Authors: Nora Weber, Mariefrancoise Gorwagrauslund, Magnus CarlquistAbstract:Whole-cell biocatalysis based on metabolically active baker’s yeast with engineered transamination activity can be used to generate molecules carrying a chiral amine moiety. A prerequisite is though to express efficient ω-transaminases and to reach sufficient intracellular precursor levels. Herein, the efficiency of three different ω-transaminases originating from Capsicum chinense, Chromobacterium violaceum, and Ochrobactrum anthropi was compared for whole-cell catalyzed kinetic resolution of racemic 1-Phenylethylamine to (R)-1-Phenylethylamine. The gene from the most promising candidate, C. violaceum ω-transaminase (CV-TA), was expressed in a strain lacking pyruvate decarboxylase activity, which thereby accumulate the co-substrate pyruvate during glucose assimilation. However, the conversion increased only slightly under the applied reaction conditions. In parallel, the effect of increasing the intracellular pyridoxal-5′-phosphate (PLP) level by omission of thiamine during cultivation was investigated. It was found that without thiamine, PLP supplementation was redundant to keep high in vivo transamination activity. Furthermore, higher reaction rates were achieved using a strain containing several copies of CV-TA gene, highlighting the necessity to also increase the intracellular transaminase level. At last, this strain was also investigated for asymmetric whole-cell bioconversion of acetophenone to (S)-1-Phenylethylamine using l-alanine as amine donor. Although functionality could be demonstrated, the activity was extremely low indicating that the native co-product removal system was unable to drive the reaction towards the amine under the applied reaction conditions. Altogether, our results demonstrate that (R)-1-Phenylethylamine with >99% ee can be obtained via kinetic resolution at concentrations above 25 mM racemic substrate with glucose as sole co-substrate when combining appropriate genetic and process engineering approaches. Furthermore, the engineered yeast strain with highest transaminase activity was also shown to be operational as whole-cell catalyst for the production of (S)-1-Phenylethylamine via asymmetric transamination of acetophenone, albeit with very low conversion.
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Improvement of whole-cell transamination with Saccharomyces cerevisiae using metabolic engineering and cell pre-adaptation
2017Co-Authors: Nora Weber, Marie Gorwa-grauslund, Magnus CarlquistAbstract:Background Whole-cell biocatalysis based on metabolically active baker’s yeast with engineered transamination activity can be used to generate molecules carrying a chiral amine moiety. A prerequisite is though to express efficient ω -transaminases and to reach sufficient intracellular precursor levels. Results Herein, the efficiency of three different ω -transaminases originating from Capsicum chinense , Chromobacterium violaceum , and Ochrobactrum anthropi was compared for whole-cell catalyzed kinetic resolution of racemic 1-Phenylethylamine to ( R )-1-Phenylethylamine. The gene from the most promising candidate, C . violaceum ω -transaminase (CV-TA), was expressed in a strain lacking pyruvate decarboxylase activity, which thereby accumulate the co-substrate pyruvate during glucose assimilation. However, the conversion increased only slightly under the applied reaction conditions. In parallel, the effect of increasing the intracellular pyridoxal-5′-phosphate (PLP) level by omission of thiamine during cultivation was investigated. It was found that without thiamine, PLP supplementation was redundant to keep high in vivo transamination activity. Furthermore, higher reaction rates were achieved using a strain containing several copies of CV-TA gene, highlighting the necessity to also increase the intracellular transaminase level. At last, this strain was also investigated for asymmetric whole-cell bioconversion of acetophenone to ( S )-1-Phenylethylamine using l -alanine as amine donor. Although functionality could be demonstrated, the activity was extremely low indicating that the native co-product removal system was unable to drive the reaction towards the amine under the applied reaction conditions. Conclusions Altogether, our results demonstrate that ( R )-1-Phenylethylamine with >99% ee can be obtained via kinetic resolution at concentrations above 25 mM racemic substrate with glucose as sole co-substrate when combining appropriate genetic and process engineering approaches. Furthermore, the engineered yeast strain with highest transaminase activity was also shown to be operational as whole-cell catalyst for the production of ( S )-1-Phenylethylamine via asymmetric transamination of acetophenone, albeit with very low conversion.
P V Potnis - One of the best experts on this subject based on the ideXlab platform.
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tandem acylation cycloalkylation with cyclohexene l acetic acid a new entry to aporphine alkaloids
1996Co-Authors: M M V Ramana, P V PotnisAbstract:Abstract Tandem Acylation-Cycloalkylation of 3,4-dimethoxy phenylethylamine (1) with cyclohexene-1-acetic acid (2) in polyphosphoric acid (PPA) afforded 8-(2-aminoethyl)-1,2,3,4,4a,10a-hexahydro-9-oxo-phenanthrene (3) which on cyclisation followed by dehydrogenation with PdC afforded dehydronornuciferine (5) . Hydrogenation of 5 yielded (±) N-nornuciferine (6) .
Xiaomao Zhou - One of the best experts on this subject based on the ideXlab platform.
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readily available chiral phosphine aminophosphine ligands derived from 1 phenylethylamine for rh catalyzed enantioselective hydrogenations
2010Co-Authors: Xiaomao Zhou, Jiadi Huang, Libin Luo, Chenglu Zhang, Zhuo ZhengAbstract:Among the novel phosphineaminophosphine derivatives prepared, effective ligands are identified for the Rh-catalyzed asymmetric hydrogenation of enamides (II), Z-β-dehydroamino acid esters (VI), and itaconate (IX).
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chiral 1 phenylethylamine derived phosphine phosphoramidite ligands for highly enantioselective rh catalyzed hydrogenation of β acylamino acrylates significant effect of substituents on 3 3 positions of binaphthyl moiety
2010Co-Authors: Xiaomao Zhou, Jiadi Huang, Libin Luo, Chenlu Zhang, Zhuo ZhengAbstract:A series of new chiral phosphine-phosphoramidite ligands with a 3,3′-substituted binaphthyl moiety were prepared from 1-Phenylethylamine, and successfully applied in the Rh-catalyzed asymmetric hydrogenation of β-(acylamino)acrylates. The research disclosed that the substituents on the 3,3′-positions of binaphthyl moiety significantly influenced the enantioselectivity.
