- Rationalizing the Unprecedented Stereochemistry of an Enzymatic Nitrile Synthesis through a Combined Computational and Experimental Approach
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In this contribution, the unique and unprecedented stereochemical phenomenon of an aldoxime dehydratase-catalyzed enantioselective dehydration of racemic E- and Z-aldoximes with selective formation of both enantiomeric forms of a chiral nitrile is rationalized by means of molecular modelling, comprising in silico mutations and docking studies. This theoretical investigation gave detailed insight into why with the same enzyme the use of racemic E- and Z-aldoximes leads to opposite forms of the chiral nitrile. The calculated mutants with a larger or smaller cavity in the active site were then prepared and used in biotransformations, showing the theoretically predicted decrease and increase of the enantioselectivities in these nitrile syntheses. This validated model also enabled the rational design of mutants with a smaller cavity, which gave superior enantioselectivities compared to the known wild-type enzyme, with excellent E-values of up to E>200 when the mutant OxdRE-Leu145Phe was utilized.
- Yavuzer, Hilmi,Asano, Yasuhisa,Gr?ger, Harald
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p. 19162 - 19168
(2021/07/26)
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- Asymmetric Hydrocyanation of Alkenes without HCN
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A general and efficient rhodium-catalyzed asymmetric cyanide-free hydrocyanation of alkenes has been developed. Based on the asymmetric hydroformylation/condensation/aza-Cope elimination sequences, a broad scope of substrates including mono-substituted, 1,2-, and 1,1-disubstituted alkenes (involving natural product R- and S-limonene) were employed, and a series of valuable chiral nitriles are prepared with high yields (up to 95 %) and enantioselectivities (up to 98 % ee). Notably, the critical factor to achieve high enantioseletivies is the addition of catalytic amount of benzoic acid. This novel methodology provides an efficient and concise synthetic route to the intermediate of vildagliptin and anagliptin.
- Li, Xiuxiu,You, Cai,Yang, Jiaxin,Li, Shuailong,Zhang, Dequan,Lv, Hui,Zhang, Xumu
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supporting information
p. 10928 - 10931
(2019/07/15)
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- Enantioselective synthesis of (R)-2-arylpropanenitriles catalysed by ene-reductases in aqueous media and in biphasic ionic liquid-water systems
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The enantioselective reduction of α-methylene nitrile derivatives catalysed by ene-reductases affords the corresponding (R)-2-arylpropanenitriles with high conversion values. The reaction is investigated either in aqueous medium (with an organic cosolvent or by loading the substrate onto hydrophobic resins) or in a biphasic ionic liquid-water system. The use of ionic liquids, herein with isolated ene-reductases, is found to improve the work-up and the substrate recovery method. The synthetic manipulation of the final chiral nitrile derivatives indicates how this biocatalysed method can be exploited for the preparation of a wide range of chiral compounds.
- Brenna, Elisabetta,Crotti, Michele,Gatti, Francesco G.,Manfredi, Alessia,Monti, Daniela,Parmeggiani, Fabio,Santangelo, Sara,Zampieri, Davila
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p. 2425 - 2431
(2014/08/18)
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- Catalytic asymmetric protonation of silyl ketene imines
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An efficient catalytic and highly enantioselective protonation of silyl ketene imines is described. The reaction is catalyzed by the chiral phosphoric acids TRIP or STRIP in the presence of a stoichiometric amount of methanol as the proton source and silyl acceptor. A variety of substituted racemic silyl ketene imines have been transformed into highly enantioenriched nitriles.
- Guin, Joyram,Varseev, Georgy,List, Benjamin
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supporting information
p. 2100 - 2103
(2013/03/28)
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