Electrochemical synthesis of amino acids by reductive amination of keto acids. I. Reduction at mercury electrodes

1978 ◽  
Vol 31 (1) ◽  
pp. 73 ◽  
Author(s):  
EA Jeffery ◽  
A Meisters
Keyword(s):  
Reductive Amination ◽  
Phenylacetic Acid ◽  
Reduction Potential ◽  
Aqueous Ammonia ◽  
Saturated Calomel Electrode ◽  
Mercury Electrode ◽  
Ammonia Concentration ◽  
Initial Current ◽  
Keto Acids ◽  
Mercury Electrodes

Racemic 2-amino-2-phenylacetic acid, monoammonium glutamate, 2-aminobutyric acid, α-alanine and ammonium 5-amino-5-phenylvalerate have been prepared by electrochemical reductive amination of the corresponding keto acids in aqueous ammonia/ammonium chloride solution at a mercury electrode. The yields ranged from 24% for ammonium 5-amino-5-phenylvalerate to 88% for 2-amino-2-phenylacetic acid. The current efficiency and yield of 2-amino-2-phenylacetic acid from reductive amination of 2-oxo-2-phenylacetic acid increased with increase in ammonia concentration. Also, decreasing the reduction potential from -1.10 to -1.30 V (with respect to a saturated calomel electrode) in 2 M ammonia raised the initial current density from c. 2 mA/cm2 to c. 7 mA/cm2 but halved the yield of 2-amino-2-phenylacetic acid.

Electrochemical synthesis of amino acids by reductive amination of keto acids. II. Reduction at platinum black and palladium black electrodes

1978 ◽  
Vol 31 (1) ◽  
pp. 79 ◽  
Author(s):  
EA Jeffery ◽  
O Johansen ◽  
A Meisters
Keyword(s):  
Reductive Amination ◽  
Phenylacetic Acid ◽  
Saturated Calomel Electrode ◽  
Ammonia Concentration ◽  
Palladium Black ◽  
Platinum Black ◽  
Reduction Potentials ◽  
Keto Acids ◽  
Yellow Coloration ◽  
Concentrated Solution

2-Amino-2-phenylacetic acid, monoammonium glutamate, 2-aminobutyric acid, α-alanine and ammonium 5-amino-5-phenylvalerate have been prepared by electrochemical reductive amination of the corresponding keto acids (or their sodium salts) in aqueous ammonia. Platinum black, platinum black/Teflon composite on tantalum gauze and palladium black were used as electrodes. The yields ranged from 40% for α-alanine and ammonium 5-amino-5-phenylvalerate to 83% for 2-amino-2-phenylacetic acid, at ammonia concentrations from 4.7 to 15.5 M. The corresponding reduction potentials were all between -0.82 and -0.90 V relative to a saturated calomel electrode. Decreasing the ammonia concentration decreased both the yield and the current efficiency for reductive amination of 2-oxo-2-phenylacetic acid. ��� 2,5-Diphenylimidazol-4-ol was prepared and isolated from a concentrated solution of 2-oxo-2-phenylacetic acid in strong ammonia. Small amounts of this compound probably cause the yellow coloration observed during electrolysis of 2-oxo-2-phenylacetic acid.

Structure-guided engineering ofmeso-diaminopimelate dehydrogenase for enantioselective reductive amination of sterically bulky 2-keto acids

2018 ◽  
Vol 8 (19) ◽  
pp. 4994-5002 ◽  
Author(s):  
Xinkuan Cheng ◽  
Xi Chen ◽  
Jinhui Feng ◽  
Qiaqing Wu ◽  
Dunming Zhu
Keyword(s):  
Reductive Amination ◽  
Substrate Binding ◽  
Binding Pocket ◽  
Substrate Binding Pocket ◽  
Keto Acids

Structure-guided reshaping the substrate-binding pocket of ameso-diaminopimelate dehydrogenase (StDAPDH) led to a mutant W121L/H227I, which catalyzed the enantioselective reductive amination of some sterically bulky 2-keto acids.

Electrochemical generation of hydridopentamminerhodium(III) and its reaction with molecular oxygen

1969 ◽  
Vol 47 (22) ◽  
pp. 4241-4246 ◽  
Author(s):  
Leslie E. Johnston ◽  
John A. Page
Keyword(s):  
Molecular Oxygen ◽  
Saturated Calomel Electrode ◽  
Mercury Electrode ◽  
Reduction Wave ◽  
Polarographic Reduction ◽  
Ammoniacal Solution ◽  
Electrochemical Generation ◽  
Dropping Mercury Electrode

The electrochemistry of Rh(NH3)5OH2+ has been studied in a buffered ammoniacal solution. The polarographic reduction wave at the dropping mercury electrode had E1/20 equal to −1.10 V (vs. saturated calomel electrode) in a 0.10 M NH3 – 0.10 M NH4ClO4 electrolyte, and gross Hg cathode electrolysis at −1.19 V produced a stable Rh(NH3)5H2+ hydride species. Both reductions were found to take place through a Rh(I) intermediate.The reaction of the Rh(NH3)5H2+ with molecular O2 in the ammoniacal electrolyte was also studied. The product was demonstrated to be a stable Rh(NH3)4(OH)(O2H)+ hydroperoxo species.

Preliminary study on alternating thienylene/phenylene copolymers functionalized with an electron-donating or -withdrawing group

2001 ◽  
Vol 16 (5) ◽  
pp. 1235-1237 ◽  
Author(s):  
J. M. Xu ◽  
S. C. Ng ◽  
H. S. O. Chan
Keyword(s):  
Electron Transport ◽  
Reduction Potential ◽  
Saturated Calomel Electrode ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Phenylene Vinylene ◽  
Light Emitting ◽  
Emissive Layer ◽  
Reduction Potentials ◽  
Preliminary Study

Three novel regioregular polymers substituted with electron-donating or -withdrawing groups, poly[1,4-bis(3-X-2,5-thienylene)phenylene-alt-2,5-dioctyl-1,4-phenylene] [PBT(X), X = OMe, H, CN], were synthesized and characterized. They are highly fluorescent, but the absorption wavelength of PBT(CN) and PBT(OMe) are shifted toward the blue and red regions, respectively, with reference to PBT(H). The onset reduction potential of PBT(CN) is –1.11 V versus SCE (saturated calomel electrode), which is higher than that of the cyano derivative of poly(phenylene vinylene), indicating it be a good candidate as electron transport layer. The onset oxidation and reduction potentials of PBT(OMe) (0.96 and –1.28 V versus SCE respectively) suggest it would perform well as emissive layer in light-emitting display applications.

Proton-Coupled Transport of Ammonia in Aqueous Hydrochloric Acid

1985 ◽  
Vol 38 (2) ◽  
pp. 249 ◽  
Author(s):  
DG Leaist
Keyword(s):  
Diffusion Coefficient ◽  
Hydrochloric Acid ◽  
Aqueous Ammonia ◽  
Transport Coefficients ◽  
Ammonia Concentration ◽  
Ammonium Ion ◽  
Coupled Transport ◽  
Ternary Diffusion ◽  
A Value ◽  
Hydrochloric Acid Solutions

Ternary diffusion in aqueous ammonia + hydrochloric acid solutions has been measured at 25°C. It is shown that the transport coefficients can be successfully predicted from the mobilities of H+, Cl -, NH4+, and un- ionized ammonia species present in the solutions. When an ammonia concentration gradient is prepared in a solution containing excess acid, the region of the solution with the higher ammonia concentration is depleted in H+ by formation of ammonium ion: NH3+H+ ↔ NH4+. As highly mobile H+ diffuses up the ammonia gradient, there is counterflow of NH4+ in order to maintain electroneutrality . This mechanism leads to rapid diffusion of the ammonia component as NH4+. Binary diffusion coefficients of aqueous ammonia have also been measured. Extrapolation gives 2.08(�0.01) × 10-2m2 s-1 for the limiting diffusion coefficient of un-ionized ammonia, a value 6% greater than the limiting diffusion coefficient of the ammonium ion.

scholarly journals Utilization of [15N]glutamate by cultured astrocytes

1986 ◽  
Vol 234 (1) ◽  
pp. 185-192 ◽  
Author(s):  
M Yudkoff ◽  
I Nissim ◽  
K Hummeler ◽  
M Medow ◽  
D Pleasure
Keyword(s):  
Reductive Amination ◽  
Adenine Nucleotides ◽  
Ammonia Concentration ◽  
Gas Chromatography Mass Spectrometry ◽  
Purine Nucleotide ◽  
Cultured Astrocytes ◽  
Dehydrogenase Reaction ◽  
Purine Nucleotide Cycle ◽  
Almost All ◽  
Glutaminase Activity

The metabolism of 0.25 mM-[15N]glutamic acid in cultured astrocytes was studied with gas chromatography-mass spectrometry. Almost all 15N was found as [2-15N]glutamine, [2-15N]glutamine, [5-15N]glutamine and [15N]alanine after 210 min of incubation. Some incorporation of 15N into aspartate and the 6-amino position of the adenine nucleotides also was observed, the latter reflecting activity of the purine nucleotide cycle. After the addition of [15N]glutamate the ammonia concentration in the medium declined, but the intracellular ATP concentration was unchanged despite concomitant ATP consumption in the glutamine synthetase reaction. Some potential sources of glutamate nitrogen were identified by incubating the astrocytes for 24 h with [5-15N]glutamine, [2-15N]glutamine or [15N]alanine. Significant labelling of glutamate was noted with addition of glutamine labelled on either the amino or the amide moiety, reflecting both glutaminase activity and reductive amination of 2-oxoglutarate in the glutamate dehydrogenase reaction. Alanine nitrogen also is an important source of glutamate nitrogen in this system.

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