104013-15-2Relevant academic research and scientific papers
Base-free Enantioselective C(1)-Ammonium Enolate Catalysis Exploiting Aryloxides: A Synthetic and Mechanistic Study
McLaughlin, Calum,Slawin, Alexandra M. Z.,Smith, Andrew D.
supporting information, p. 15111 - 15119 (2019/11/05)
An isothiourea-catalyzed enantioselective Michael addition of aryl ester pronucleophiles to vinyl bis-sulfones via C(1)-ammonium enolate intermediates has been developed. This operationally simple method allows the base-free functionalization of aryl esters to form α-functionalized products containing two contiguous tertiary stereogenic centres in excellent yield and stereoselectivity (all ≥99:1 er). Key to the success of this methodology is the multifunctional role of the aryloxide, which operates as a leaving group, Br?nsted base, Br?nsted acid and Lewis base within the catalytic cycle. Comprehensive mechanistic studies, including variable time normalization analysis (VTNA) and isotopologue competition experiments, have been carried out. These studies have identified (i) orders of all reactants; (ii) a turnover-limiting Michael addition step, (iii) product inhibition, (iv) the catalyst resting state and (v) catalyst deactivation through protonation.
Stereodivergent Protein Engineering of a Lipase to Access All Possible Stereoisomers of Chiral Esters with Two Stereocenters
Xu, Jian,Cen, Yixin,Singh, Warispreet,Fan, Jiajie,Wu, Lian,Lin, Xianfu,Zhou, Jiahai,Huang, Meilan,Reetz, Manfred T.,Wu, Qi
supporting information, p. 7934 - 7945 (2019/05/22)
Enzymatic stereodivergent synthesis to access all possible product stereoisomers bearing multiple stereocenters is relatively undeveloped, although enzymes are being increasingly used in both academic and industrial areas. When two stereocenters and thus four stereoisomeric products are involved, obtaining stereodivergent enzyme mutants for individually accessing all four stereoisomers would be ideal. Although significant success has been achieved in directed evolution of enzymes in general, stereodivergent engineering of one enzyme into four highly stereocomplementary variants for obtaining the full complement of stereoisomers bearing multiple stereocenters remains a challenge. Using Candida antarctica lipase B (CALB) as a model, we report the protein engineering of this enzyme into four highly stereocomplementary variants needed for obtaining all four stereoisomers in transesterification reactions between racemic acids and racemic alcohols in organic solvents. By generating and screening less than 25 variants of each isomer, we achieved >90% selectivity for all of the four possible stereoisomers in the model reaction. This difficult feat was accomplished by developing a strategy dubbed "focused rational iterative site-specific mutagenesis" (FRISM) at sites lining the enzyme's binding pocket. The accumulation of single mutations by iterative site-specific mutagenesis using a restricted set of rationally chosen amino acids allows the formation of ultrasmall mutant libraries requiring minimal screening for stereoselectivity. The crystal structure of all stereodivergent CALB variants, flanked by MD simulations, uncovered the source of selectivity.
Resolution of pentafluorophenyl 2-phenylpropanoate using combinations of quasi-enantiomeric oxazolidin-2-ones
Shaye, Najla Al,Benoit, David M.,Chavda, Sameer,Coulbeck, Elliot,Dingjan, Marco,Eames, Jason,Yohannes, Yonas
experimental part, p. 413 - 438 (2011/06/17)
The kinetic, mutual and parallel resolution of a series of structurally related active esters derived from 2-phenylpropanoic acid using a combination of quasi-enantiomeric oxazolidin-2-ones is discussed.
Fingerprint lipolytic enzymes with chromogenic p-nitrophenyl esters of structurally diverse carboxylic acids
Qian, Le,Liu, Jia-Yan,Liu, Jia-Ying,Yu, Hui-Lei,Li, Chun-Xiu,Xu, Jian-He
experimental part, p. 22 - 26 (2012/02/06)
A series of structurally diverse chromogenic esters, including a new compound (4-nitrophenyl 2-methylpentanoate), has been synthesized, constituting an array of 17 substrates which could be applied to rapidly fingerprint the activity of lipases or esterases to reveal their substrates specificity and functional characteristics. Combined with genetic technology such as "data mining" and directed evolution, such fingerprints might be a promising platform for discovery of potentially useful enzymes in industrial application. The fingerprint of commercially available Lipase-B from Candida antarctica as a model enzyme was first measured to confirm the reliability of this method. Then three new enzymes mined from genomic libraries were successfully fingerprinted, revealing the functional characteristics of those enzymes. Among them, the enzyme SrfAD was founded with specific substrate preference towards cycloalkyl carboxylic esters and aromatic esters, making it more promising in synthetic utilities than other tested enzymes.
Directed evolution of an enantioselective lipase with broad substrate scope for hydrolysis of α-substituted esters
Engstroem, Karin,Nyhlen, Jonas,Sandstroem, Anders G.,Baeckvall, Jan-E.
supporting information; experimental part, p. 7038 - 7042 (2010/07/05)
A variant of Candida antarctica lipase A (CalA) was developed for the hydrolysis of α-substituted p-nitrophenyl esters by directed evolution. The E values of this variant for 7 different esters was 45-276, which is a large improvement compared to 2-20 for the wild type. The broad substrate scope of this enzyme variant is of synthetic use, and hydrolysis of the tested substrates proceeded with an enantiomeric excess between 95-99%. A 30-fold increase in activity was also observed for most substrates. The developed enzyme variant shows (R)-selectivity, which is reversed compared to the wild type that is (S)-selective for most substrates.
2-phenylpropionic acid esters, method for optical resolution thereof and optically active substance thereof
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, (2008/06/13)
2-Phenylpropoionic acid ester of Formula (I): STR1 wherein R represents p-nitrophenyl group, β-naphthyl group or 2-(β-naphthyl)ethyl group. Optical resolution of the above is carried out by preferential crystallization by seeding either one of the optical
