- Thermodynamics and kinetic aspects involved in the enzymatic resolution of (R,S)-3-fluoroalanine in a coupled system of redox reactions catalyzed by dehydrogenases
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Two systems of redox enzymatic reactions were tested, looking forward to the preparation of (S)-3-fluoroalanine, a potent antibiotic, by kinetic resolution of rac-3-fluoroalanine. This starting material was the main substrate for the deaminative oxidation reaction catalyzed by L-alanine dehydrogenase (L-AlaDH) in the presence of NAD+. One system was formed by coupling this reaction (main reaction) to the reduction of 3-fluoropyruvate (a cascade system) produced in the main reaction catalyzed by L-lactate dehydrogenase (L-LDH) in the presence of NADH, also formed in the main reaction. This system, that was able to achieve 92% of conversion, allows the accumulation of NH 4+, one of the secondary products of the main reaction. The other coupled redox system involved the coupling to the L-AlaDH reaction to the aminative reduction reaction of α-ketoglutarate in the presence of NADH and NH4+ (both side products of the main reaction) catalyzed by L-glutamate dehydrogenase (L-GluDH), that allows accumulation of 3-fluoropyruvate. With this system, the extent of the reaction in the coupled system was only 22%. This big difference in the efficiency of both systems was identified as being the result of a different potency of the products that accumulates in both systems, acting as inhibitors of L-AlaDH. It was demonstrated that 3-fluoropyruvate is a much stronger inhibitor of L-AlaDH than NH4+. This fact, and not thermodynamic considerations, explains the results obtained with both systems.
- Goncalves, Luciana P. B.,Antunes,Oestreicher, Enrique G.
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- Simple synthesis of mono- and difluoroalanines
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Highly basic tris(diethylamino)-N-methylphosphazene was used for mono- and difluoromethylation of diethyl N-acetylaminomalonate by CH2BrF or CHClF2 in dichloromethane at -40°C. Acidic hydrolysis of fluoromethylated products afforded
- Gerus,Kolomeitsev,Kolycheva,Kukhar
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- Kinetic aspects involved in the simultaneous enzymatic synthesis of (S)-3-fluoroalanine and (R)-3-fluorolactic acid
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Desaminative oxidation of rac -3-fluoroalanine (rac-1) catalyzed by l-alanine dehydrogenase (l-ALADH) was studied by means of initial rate experiments both in the presence and in the absence of a product. Estimates of kinetic parameters of the reaction were obtained. The reaction mechanism is the sequential ordered BiTer mechanism with inhibition by excess of (S)-3-fluoroalanine. This kinetic study was the basis for the development of a couple enzymatic system for the simultaneous synthesis of (S)-3-fluoroalanine (1a) and (R)-3-fluorolactic acid (3) with l-ALADH and l-lactate dehydrogenase using rac-1 and NAD+. Analysis of isolated products revealed 1a in 60% yield and 86% ee and 3 in 80% yield and over 99% ee. Compounds 1a and 3 represent chiral building blocks for the synthesis of several products with pharmacological activity. The presence of the fluorine atom in the substrate causes a better interaction of it in the active site of the enzyme.
- Gon?alves, Luciana P.B.,Antunes, Octavio A.C.,Pinto, Gerson F.,Oestreicher, Enrique G.
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- SYNTHESIS AND ENZYMATIC CLEAVAGE OF D,L-3-FLUOROALANINE
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The action of bromine trifluoride on methyl 2,3-dibromopropionate in the presence of stannic chloride gives a high yield of methyl 2-bromo-3-fluoropropionate.Under the conditions of phase-transfer catalysis the product gave a 3-fluoro-2-azido ester, and reduction of the latter with hydrogen in the presence of Pd/C gave 3-fluoroalanine methyl ester.Enzymatic cleavage of N-BOC-3-fluoro-D,L-alanine methyl ester with papain took place stereospecifically, and N-BOC-3-fluoro-L-alanine was isolated with an almost quantitative yield.
- Gerus, I. I.,Yagupol'skii, Yu. L.,Kukhar, V. P.,Boguslavskaya, L. S.,Chuvatkin, N. N.,et al.
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p. 465 - 468
(2007/10/02)
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- Fluorinated amino acids
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Deutero analogs of 3-fluoro-D-alanine prepared by direct photofluorination of the D-amino acids demonstrate in vivo and in vitro antibacterial activity against both gram negative and gram positive microorganisms. Deuters analogs of 3-fluoro-L-alanine and 3-fluoro-D,L-alanine also demonstrate useful in vitro activity.
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