- Improving Catalytic Activity and Reversing Enantio-Specificity of ω-Transaminase by Semi-Rational Engineering en Route to Chiral Bulky β-Amino Esters
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The application of wild-type ω-transaminase was limited by steric hindrance towards bulky substrates, therefore improvement of the catalytic efficiency and stereoselectivity toward substrates with two bulky substituent adjacent to the carbonyl is of general interest. In this study, according to the double substrate binding pocket theory, a (S)-selective ω-transaminase from the Burkholderia vietnamiensis G4, which showed puny catalytic activity toward the β-keto esters with small steric hindrance, was engineered to accept bulky β-keto esters, which were not accessible by any wild-type enzyme. A few desired variants were obtained that exhibited activity toward bulky β-keto esters. Furthermore, a substrate-dependent shift in enantio-preference of HBV variant towards β-keto esters with linear or branched aliphatic substituents was observed. The best variant was applied to the asymmetric synthesis of aliphatic β-amino acids at semi-preparative scale with high yield and enantioselectivity. This study will improve the general understanding and inspire further engineering work for reversing enantio-specificity of ω-transaminases.
- Wang, Yingang,Feng, Jinhui,Dong, Wenyue,Chen, Xi,Yao, Peiyuan,Wu, Qiaqing,Zhu, Dunming
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p. 3396 - 3400
(2021/06/21)
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- Structural effects on chemo- and enantioselectivity of Candida antarctica lipase B - Resolution of β-amino esters
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The Candida antarctica lipase B-catalyzed reactions of five β-amino esters with neat butyl butanoate and with 2,2,2-trifluoroethyl butanoate in diisopropyl ether were studied, as were the reactions of the same β-amino esters and their N-butanamides with neat butanol. The possibility for sequential resolution, where the amino and ester functions of the substrate both react with an achiral butanoate, became less likely with increasing size of the substrate from ethyl 3-aminobutanoate (1a) to pentanoate (1b) or larger. On the other hand, the alcoholyses of N-acylated β-amino esters successfully proceeded in butanol with E > 100. Gram-scale resolution of the N-butanoylated 1a was performed to demonstrate the usefulness of the method.
- Gedey, Szilvia,Liljeblad, Arto,Lazar, Laszlo,Fueloep, Ferenc,Kanerva, Liisa T.
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p. 565 - 570
(2007/10/03)
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- Stereoselective ring opening of chiral oxazolidines by reformatsky reagents: An enantioselective entry to β-amino esters
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Chiral oxazolidines obtained by condensation of aldehydes with (-).(R)- or (+).(S)-N-benzylphenylglycinol react with the Reformatsky reagent derived from ethyl bromoacetate, in mild reaction conditions (Et2O or CH2Cl2, 0°C, 15-60 min), leading to ethyl β-amino carboxylates in moderate to good diastereomeric excess (60-92%). These ring opening products are transformed into primary β-aminoesters, in one step, by debenzylation with H2/Pd on carbon without loss of their stereochemical integrity. In this way, ethyl β-amino carboxylates can be obtained in both enantiomeric forms, with chemical yields ranging 55-76% and moderate to good e.e. (60-92%).
- Andres, Celia,Gonzalez, Alfonso,Pedrosa, Rafael,Perez-Encabo, Alfonso
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p. 2895 - 2898
(2007/10/02)
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