- Enhanced conversion of racemic α-arylalanines to (R)-β- arylalanines by coupled racemase/aminomutase catalysis
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(Graph Presented) The Taxus phenylalanine aminomutase (PAM) enzyme converts several (S)-α-arylalanines to their corresponding (R)-β- arylalanines. After incubating various racemic substrateswith 100 μg of PAM for 20 h at 31°C, each (S)-α-arylalanine was enantioselectively isomerized to its corresponding (R)-β-product. With racemic starting materials, the ratio of (R)-β-arylalanine product to the (S)-α-substrate ranged between 0.4 and 1.8, and the remaining nonproductive (R)-α-arylalanine became enriched. To utilize the (R)-α-isomer, the catalysis of a promiscuous alanine racemase from Pseudomonas putida (KT2440) was coupled with that of PAM to increase the production of enantiopure (R)-β-arylalanines from racemic α-arylalanine substrates. The inclusion of a biocatalytic racemization along with the PAM-catalyzed reactionmoderately increased the overall reaction yield of enantiopure β-arylalanines between 4% and 19% (depending on the arylalanine), which corresponded to as much as a 63% increase compared to the turnover with the aminomutase reaction alone. The use of these biocatalysts, in tandem, could potentially find application in the production of chiral β-arylalanine building blocks, particularly, as refinements to the process are made that increase reaction flux, such as by selectively removing the desired (R)-β-arylalanine product from the reaction mixture. 2009 American Chemical Society.
- Cox, Brad M.,Bilsborrow, Joshua B.,Walker, Kevin D.
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supporting information; experimental part
p. 6953 - 6959
(2009/12/25)
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- The interaction of heteroaryl-acrylates and alanines with phenylalanine ammonia-lyase from parsley
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Acrylic acids and alanines substituted with heteroaryl groups at the β-position were synthesized and spectroscopically characterized (UV, HRMS, 1H NMR, and 13C NMR spectroscopy). The heteroaryl groups were furanyl, thiophenyl, benzofuranyl, and benzothiophenyl and contained the alanyl side chains either at the 2- or 3-positions. While the former are good substrates for phenylalanine ammonia lyase (PAL), the latter compounds are inhibitors. Exceptions are thiophen-3-yl-alanine, a moderate substrate and furan-3-yl-alanine, which is inert. Possible reasons for these exceptions are discussed. Starting from racemic het eroaryl-2-alanines their D-enantiomers were prepared by using a stereodestructive procedure. From the heteroaryl-2- acrylates, the L-enantiomers of the heteroaryl-2-alanines were prepared at high ammonia concentration. These results can be best explained by a Friedel - Crafts-type electrophilic attack at the aromatic part of the substrates as the initial step of the PAL reaction.
- Paizs, Csaba,Katona, Adrian,Retey, Janos
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p. 2739 - 2744
(2008/02/03)
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- Improved preparation of racemic 2-amino-3-(heteroaryl)propanoic acids and related compounds containing a furan or thiophene nucleus
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Racemic 2-amino-3-(heteroaryl)propanoic acids (1), mostly with a furan or thiophene nucleus as a heteroaryl group, were synthesized in 48-94% yield by the reduction of 3-(heteroaryl)-2-(hydroxyimino)propanoic acids (5) with zinc dust and formic acid in the presence of a catalytic amount of iron dust at 60°C for 2 h. Under these conditions, unfavorable hydrogenolysis of bromine on the thiophene nucleus does not occur. Traditional Nformylation of the prepared 3-(heteroaryl)alanine (1) with a mixture of formic acid and acetic anhydride afforded 2-(formylamino)-3-(heteroaryl)propanoic acids (6) in 51-95% yield.
- Kitagawa, Tokujiro,Khandmaa, Dashrenchin,Fukumoto, Ayumi,Asada, Makoto
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p. 1137 - 1139
(2007/10/03)
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- An improved method for the synthesis of DL-3-(2-furyl)alanine
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DL-3-(2-Furyl)alanine (1) was prepared by the condensation of 2- (bromomethyl)furan (7) with diethyl formamidomalonate (2), followed by the traditional saponification-decarboxylation techniques.
- Kitagawa, Tokujiro,Akiyama, Naohiro
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p. 1865 - 1866
(2007/10/03)
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