- NAD(P)+-NAD(P)H. 39. Asymmetric Reduction by 1,4-Dihydronicotinamide Derivative Bound to Protein
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1,4-Dihydronicotinamide derivatives covalently bound to NH2 or SH group of proteins such as reduced keratin (RK), egg white albumin (EWA), and bovine serum albumin (BSA) have been synthesized and subjected to the reductions of α,α,α-trifluoroacetophenone
- Ohno, Atsuyoshi,Ushida, Satoshi,Oka, Shinzaburo
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- Synthesis of Planar Chiral Shvo Catalysts for Asymmetric Transfer Hydrogenation
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A new type of planar chiral Shvo catalysts, where the chirality is based solely on different substitution flanking the C￡O function, was prepared and used for transfer hydrogenation of imines and ketones. The reduction of ketimines represented by N-(1-phe
- Dou, Xiaowei,Hayashi, Tamio
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- Monitoring surface processes during heterogeneous asymmetric hydrogenation of ketones on a chirally modified platinum catalyst by operando spectroscopy
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Surface processes occurring at the catalytic chiral surface of a cinchona-modified Pt catalyst during the asymmetric hydrogenation of activated ketones have been monitored for the first time using operando ATR-IR spectroscopy. Fundamental information about this catalytic system could be gained, including the chiral modification process of the catalyst, the surface interaction of reactant ketone with preadsorbed chiral modifier, the role of hydrogen as well as the influence of the product enantiomers in the catalytic cycle. The formation of a diastereomeric transient surface complex between ketone and chiral modifier was found to be related to the ketone consumption. Among the studied activated ketones, a correlation between stereoselection and the strength of the intermolecular hydrogen bond was identified. Dissociated hydrogen from the catalytic surface is found to play a crucial role in the formation of the diastereomeric surface complex.
- Meemken, Fabian,Hungerbuehler, Konrad,Baiker, Alfons
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- Synthesis of a P-stereogenic PNPtBu,Ph ruthenium pincer complex and its application in asymmetric reduction of ketones
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A novel P-stereogenic PNPtBu,Ph ruthenium complex has been synthesized and characterized enabling the asymmetric hydrogenation of a wide range of aromatic ketones with excellent catalytic activities (up to 98% conversion) and good levels of enantiodiscrimination (up to 95% ee). P-stereogenic PNPtBu,Ph Ru complex was for the first time synthesized and characterized and has proven to be an efficient catalyst for the asymmetric reduction of a wide range of ketones
- Arenas, Ismael,Boutureira, Omar,Matheu, M. Isabel,Díaz, Yolanda,Castillón, Sergio
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- Enantioselective reduction of trifluoromethyl ketones using an oxazaborolidine catalyst generated in situ from a chiral lactam alcohol
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The oxazaborolidine catalyst prepared in situ from the chiral lactam alcohol 2 and borane was found to catalyze the enantioselective reduction of highly reactive trifluoromethyl ketones at room temperature with high enantioselectivities of up to 86% ee.
- Kawanami, Yasuhiro,Hoshino, Katsuhiro,Tsunoi, Wataru
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- Enantioselective hydrosilylation with a chiral N-heterocyclic carbene complex of rhodium(I) [1]
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Both enantiomers of the chiral rhodium-NHC complex [(4X, 5X)-1,3-bis[2,6-diisopropyl-phenyl]-4,5-ditert-butylimidazolidine-2-ylidene][1, 5-cyclooctadiene]-iodo-rhodium(I) with X = R, S were applied as catalysts for the asymmetric hydrosilylation of prochi
- Zinner, Sandra C.,Zhang-Presse, Mei,Herrmann, Wolfgang A.,Kuehn, Fritz E.
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- Electrochemically Promoted Asymmetric Transfer Hydrogenation of 2,2,2-Trifluoroacetophenone
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The study reported an electrochemically promoted asymmetric hydrogen transfer reaction of 2,2,2-trifluoroacetophenone with a chiral Ru complex. (R)-α-(Trifluoromethyl) benzyl alcohol with a 96% yield and 94% ee could be obtained with only a 0.5 F mol-1charge amount at room temperature and normal pressure.
- Wang, Huan,Yue, Ying-Na,Xiong, Rui,Liu, Yu-Ting,Yang, Li-Rong,Wang, Ying,Lu, Jia-Xing
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- Metal-conjugated affinity labels: A new concept to create enantioselective artificial metalloenzymes
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How to train a protein: Metal-conjugated affinity labels were used to selectively position catalytically active metal centers in the binding pocket of proteases. The resulting artificial metalloenzymes achieve up to 82% e.r. in the hydrogenation of ketone
- Reiner, Thomas,Jantke, Dominik,Marziale, Alexander N.,Raba, Andreas,Eppinger, Jcrg
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- Enantioselective hydrogenation of ketones by iridium nanoparticles ligated with chiral secondary phosphine oxides
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Chiral iridium nanoparticles (IrNPs) were synthesized by H2 reduction of (1,5-cyclooctadiene)(methoxy)iridium(i) dimer ([Ir(OMe)(COD)]2) in the presence of an asymmetric secondary phosphine oxide (4,5-dihydro-3H-dinaphtho[2,1-c:1′,2′
- Cano, Israel,Tschan, Mathieu J.-L.,Martínez-Prieto, Luis M.,Philippot, Karine,Chaudret, Bruno,Van Leeuwen, Piet W.N.M.
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- Origin of the rate enhancement and enantiodifferentiation in the heterogeneous enantioselective hydrogenation of 2,2,2-trifluoroacetophenone over Pt/alumina studied in continuous-flow fixed-bed reactor system
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A study on the origin of rate enhancement and enantiodifferentiation in the enantioselective hydrogenation of 2,2,2-trifluoroacetophenone (TFAP) over a Pt/alumina catalyst modified by cinchona alkaloids in toluene/acetic acid (AcOH) solvent mixture with a
- Szollosi, Gy?rgy,Cserényi, Szabolcs,Bucsi, Imre,Bartók, Tibor,Fül?p, Ferenc,Bartók, Mihály
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- Transfer hydrogenation of activated ketones using novel chiral Ru(II)-N-arenesulfonyl-1,2-diphenylethylenediamine complexes
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A series of α-keto esters and α,α,α- trifluoromethyl ketones were reduced in high yields and excellent enantioselectivities under Ru-catalysed transfer hydrogenation using novel chiral N-arenesulfonyl-1,2-diphenylethylenediamine ligands.
- ?terk, Damjan,Stephan, Massoud S.,Mohar, Barbara
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- Genetically programmed chiral organoborane synthesis
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Recent advances in enzyme engineering and design have expanded nature's catalytic repertoire to functions that are new to biology1-3. However, only a subset of these engineered enzymes can function in living systems4-7. Finding enzymatic pathways that form chemical bonds that are not found in biology is particularly difficult in the cellular environment, as this depends on the discovery not only of new enzyme activities, but also of reagents that are both sufficiently reactive for the desired transformation and stable in vivo. Here we report the discovery, evolution and generalization of a fully genetically encoded platform for producing chiral organoboranes in bacteria. Escherichia coli cells harbouring wild-type cytochrome c from Rhodothermus marinus8 (Rma cyt c) were found to form carbon-boron bonds in the presence of borane-Lewis base complexes, through carbene insertion into boron-hydrogen bonds. Directed evolution of Rma cyt c in the bacterial catalyst provided access to 16 novel chiral organoboranes. The catalyst is suitable for gram-scale biosynthesis, providing up to 15,300 turnovers, a turnover frequency of 6,100 h-1, a 99:1 enantiomeric ratio and 100% chemoselectivity. The enantiopreference of the biocatalyst could also be tuned to provide either enantiomer of the organoborane products. Evolved in the context of whole-cell catalysts, the proteins were more active in the whole-cell system than in purified forms. This study establishes a DNA-encoded and readily engineered bacterial platform for borylation; engineering can be accomplished at a pace that rivals the development of chemical synthetic methods, with the ability to achieve turnovers that are two orders of magnitude (over 400-fold) greater than those of known chiral catalysts for the same class of transformation9-11. This tunable method for manipulating boron in cells could expand the scope of boron chemistry in living systems.
- Jennifer Kan,Huang, Xiongyi,Gumulya, Yosephine,Chen, Kai,Arnold, Frances H.
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- Reversal of the ee in enantioselective hydrogenation of activated ketones in continuous-flow fixed-bed reactor system
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A study on the hydrogenation of ethyl pyruvate, methyl benzoylformate and 2,2,2-trifluoroacetophenone over Pt-cinchona alkaloid chiral catalysts and over the "unmodified" catalysts resulted after a cleaning step at 323 K of the chirally modified surfaces in continuous-flow fixed-bed reactor system is presented. According to these investigations the sense of the residual ee observed in the reactions carried out in the absence of modifiers over the catalysts rinsed after the chiral hydrogenations was influenced by the solvent and the structure of the activated ketone, pointing on the effect of these parameters on the structure of the adsorbed intermediate complexes and implicitly on the chiral induction.
- Cserényi, Szabolcs,Szollosi, Gy?rgy,Szori, Kornél,Fül?p, Ferenc,Bartók, Mihály
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- β-Hydroxyamide-based ligands and their use in the enantioselective borane reduction of prochiral ketones
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Hydroxyamide-based ligands have occupied a considerable place in asymmetric synthesis. Here we report the synthesis of seven β-hydroxyamide-based ligands from the reaction of 2-hydroxynicotinic acid with chiral amino alcohols and test their effect on the enantioselective reduction of aromatic prochiral ketones with borane in tetrahydofuran (THF). They produce the corresponding secondary alcohols with up to 76% enantiomeric excess (ee) and good to excellent yields (86-99%). Chirality 26:21-26, 2013. 2013 Wiley Periodicals, Inc.
- Azizoglu, Murat,Erdogan, Asli,Arslan, Nevin,Turgut, Yilmaz
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- Enantioselective transfer hydrogenation of ketone catalysed by artificial metalloenzymes derived from bovine β-lactoglobulin
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Artificial metalloproteins resulting from the embedding of half-sandwich Ru(II)/Rh(III) fatty acid derivatives within β-lactoglobulin catalysed the asymmetric transfer hydrogenation of trifluoroacetophenone with modest to good conversions and fair ee's. T
- Chevalley, Alice,Salmain, Michèle
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- Fundamental insights into the enantioselectivity of hydrogenations on cinchona-modified platinum and palladium
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The influence of the configuration at the C8 and C9 positions of cinchona alkaloids was investigated by comparing the efficiency of cinchonidine, cinchonine, and 9-epi-cinchonidine as chiral modifiers. In the hydrogenation of ketones (methyl benzoylformate, ketopantolactone, methylglyoxal dimethylacetal, 2,2,2-trifluoroacetophenone) on Pt, a change in the configuration at C9 did not affect the absolute configuration of the main products; however, the ees and rates dropped significantly. In the hydrogenation of α-functionalized olefins (E-2-methyl-2-hexenoic acid, 2-phenylcinnamic acid, and 4-methoxy-6-methyl-2H-pyran-2-one) on Pd, replacement of cinchonidine or cinchonine by epi-cinchonidine diminished the rates and almost eliminated the enantioselection, indicating that a subtle combination of C8 and C9 configurations is required on Pd. DFT calculations of the adsorption of the modifiers and the nonlinear behavior of modifier mixtures revealed that the lower reaction rates observed for 9-epi-cinchonidine-modified surfaces cannot be related to different adsorption strength of this modifier. Additionally, substrate-modifier docking interactions are presented.
- Schmidt, Erik,Bucher, Christoph,Santarossa, Gianluca,Mallat, Tamas,Gilmour, Ryan,Baiker, Alfons
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- Chiral terpene auxiliaries IV: new monoterpene PHOX ligands and their application in the catalytic asymmetric transfer hydrogenation of ketones
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New PHOX ligands, derived in three steps from (1R, 2S, 3R, 5R)-3-amino-apopinan-2-ol 1 and (1R, 2R, 3S, 5R)-3-amino-pinan-2-ol 2 were applied as chiral ligands for the formation of ruthenium catalysts. The catalysts were used in asymmetric transfer hydrogenations of prochiral ketones producing the corresponding alcohols in moderate to high yields and enantioselectivity.
- Kmieciak, Anna,Krzemiński, Marek P.
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- A mechanistic and structural analysis of the basis for high enantioselectivity in the oxazaborolidine-catalyzed reduction of trihalomethyl ketones by catecholborane
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The rates and enantioselectivities of the reduction of a series of trihalomethyl ketones under catalysis by oxazaborolidine 2 can be explained in terms of structural and mechanistic analyses which are detailed herein and which have predictive value.
- Corey,Link, John O.,Bakshi, Raman K.
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- Chiral imidazolidinone and proline-derived surface modifiers for the Pt-catalysed asymmetric hydrogenation of activated ketones
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A series of imidazolidinone and proline derivatives have been synthesised and tested with regard to their suitability for the chiral modification of platinum used for the asymmetric hydrogenation of activated ketones. Hydrogenations of ketopantolactone (KPL), methyl benzoylformate (MBF) and trifluoroacetophenone (TFAP) performed at low hydrogen pressures (1 and 10 bar) were selected as test reactions. With some of these synthethic modifiers, encouraging levels of enantioselectivity were achieved (up to 73.5:26.5 e.r.) without optimisation of the reaction conditions. Moreover, performance enhancement of l-proline derived-modifiers, as a consequence of molecular editing with fluorine, was found to be significant (OH → F, Δee up to 23%) contributing to the growing interest in modulating catalyst performance by fluorine introduction.
- Holland, Mareike C.,Meemken, Fabian,Baiker, Alfons,Gilmour, Ryan
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- Bioreductive synthesis of perfluorinated chiral alcohols
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Perfluorinated chiral alcohols are interesting building blocks for pharmaceuticals and agrochemicals. Different chiral (R)- and (S)-configured perfluorinated alcohols were produced by asymmetric reduction of the corresponding ketones. Commercially available alcohol dehydrogenases were used as catalyst in combination with different cofactor regenerating systems. High selectivities of >99% were observed in most cases. The results also demonstrate the influence of the CF3 group on reactivity and enantioselectivity of alcohol dehydrogenases.
- Rosen, Thomas C.,Feldmann, Ralf,Dünkelmann, Pascal,Dau?mann, Thomas
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- Continuous flow whole cell bioreduction of fluorinated acetophenone
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Several microorganism strains were used to reduce 2,2,2- trifluoroacetophenone (1) and 4′-Br-2,2,2-trifluoroacetophenone (3). Immobilized cells of Geotrichum candidum in calcium alginate led to conversion and enantiomeric excess higher than 99%. By using immobilized G. candidum cells under continuous flow conditions, the same conversion and enantiomeric excess were achieved in 90 min of residence time.
- De Oliveira Lopes, Raquel,Ribeiro, Joyce Benzaquem,Silva De Miranda, Amanda,Vieira Da Silva, Gabriela Veloso,Miranda, Leandro S.M.,Ramos Leal, Ivana Corrêa,Mendon?a Alves De Souza, Rodrigo Octavio
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- Catalytic asymmetric β-hydrogen transfer reduction of α-trifluoromethyl aromatic ketones with diethylzinc
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Abstract The catalytic asymmetric β-hydrogen transfer reduction of α-trifluoromethyl ketones using diethylzinc as the β-hydrogen donor was developed with the use of phosphinamide chiral ligand. The corresponding alcohol products were afforded in good yields with up to 73% ee. This method was successfully applied to the chemo- and enantioselective reduction of α-methyl/trifluoromethyl diketone, affording 88% yield and 70% ee of the fluorinated hydroxylketone product.
- Huang, Huayin,Zong, Hua,Bian, Guangling,Song, Ling
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- Chiral (cyclopentadienone)iron complexes with a stereogenic plane as pre-catalysts for the asymmetric hydrogenation of polar double bonds
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In this paper, we describe a small library of easy-to-prepare chiral (cyclopentadienone)iron pre-catalysts for enantioselective C[dbnd]O and C[dbnd]N hydrogenations. Starting from readily accessible achiral materials, six chiral (cyclopentadienone)iron complexes (1a-f) possessing a stereogenic plane were synthesized in racemic form. Based on the screening of pre-catalysts (±)-1a-f in the hydrogenation of ketones and ketimines, we selected two complexes (1a and 1d) for resolution by semipreparative enantioselective HPLC. The absolute configuration of the separated enantiomers of 1a and 1d was assigned by XRD analysis (1a) and by comparison between experimental and DFT-calculated ECD and ORD spectra (1d). The enantiopure pre-catalysts (S)-1a and (R)-1d were tested in the asymmetric hydrogenation of several ketones and ketimines and showed good activity and modest enantioselectivity, the e.e. values ranging from very low to moderate (54%).
- Bai, Xishan,Cettolin, Mattia,Mazzoccanti, Giulia,Pierini, Marco,Piarulli, Umberto,Colombo, Valentina,Dal Corso, Alberto,Pignataro, Luca,Gennari, Cesare
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- Multiple cycle reaction mechanism in the enantioselective hydrogenation of α,α,α-trifluoromethyl ketones
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The enantioselective hydrogenation of 2,2,2-trifluoroacetophenone (1) on cinchona-modified Pt, combined with the diastereoselective hydrogenation of cinchonidine and NMR analysis of the modifier-substrate-product interactions, revealed the key role of the
- Cakl,Reimann,Schmidt,Moreno,Mallat,Baiker
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- STEREOSELECTIVE REDUCTION OF C=X BY A CHIRAL 1,4-DIHYDROPYRIDINE (NADH-MIMIC) IN A SELF-IMMOLATIVE PROCESS
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A series of prochiral ketones and a prochiral imine was reduced with high absolute stereoselectivity using an optically active 4-methyl-1,4-dihydropyridine in the presence of Mg(ClO4)2.
- Meyers, A. I.,Brown, Jack D.
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- Asymmetric Ketone Reduction by Imine Reductases
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The rapidly growing area of asymmetric imine reduction by imine reductases (IREDs) has provided alternative routes to chiral amines. Here we report the expansion of the reaction scope of IREDs by showing the stereoselective reduction of 2,2,2-trifluoroacetophenone. Assisted by an in silico analysis of energy barriers, we evaluated asymmetric hydrogenations of carbonyls and imines while considering the influence of substrate reactivity on the chemoselectivity of this novel class of reductases. We report the asymmetric reduction of C=N as well as C=O bonds catalysed by members of the IRED enzyme family.
- Lenz, Maike,Meisner, Jan,Quertinmont, Leann,Lutz, Stefan,K?stner, Johannes,Nestl, Bettina M.
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- Direct observation of molecular preorganization for chirality transfer on a catalyst surface
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The chemisorption of specific optically active compounds on metal surfaces can create catalytically active chirality transfer sites. However, the mechanism through which these sites bias the stereoselectivity of reactions (typically hydrogenations) is gen
- Demers-Carpentier, Vincent,Goubert, Guillaume,Masini, Federico,Lafleur-Lambert, Raphael,Dong, Yi,Lavoie, Stephane,Mahieu, Gautier,Boukouvalas, John,Gao, Haili,Rasmussen, Anton M. H.,Ferrighi, Lara,Pan, Yunxiang,Hammer, Bjork,McBreen, Peter H.
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- Alkaloid-induced asymmetric hydrogenation on bimetallic Pt@Cu cathodes under electrochemical conditions
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Bimetallic Pt@Cu nanoparticles (NPs) with low Pt loading obtained by reducing platinum precursors on Cu NPs were coated on carbon paper and used as a cathode for asymmetric hydrogenation by the electrochemical method. The Pt@Cu NPs exhibited enhanced cata
- Yue, Ying-Na,Wu, Di,Zeng, Sheng,Yang, Man-Ping,Wang, Huan,Lu, Jia-Xing
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- Hydrogenation of 2,2,2-trifluoroacetophenone: Molecular insight into the role of solvent in enantioselection
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The unique solvent effect in the enantioselective hydrogenation of α-fluorinated ketones has been investigated in ten different solvents using the hydrogenation of 2,2,2-trifluoroacetophenone (1) on cinchonine (CN)-modified Pt/Al2O3
- Pere?iguez, Rosa,Santarossa, Gianluca,Mallat, Tamas,Baiker, Alfons
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- Artificial metalloenzymes derived from bovine β-lactoglobulin for the asymmetric transfer hydrogenation of an aryl ketone-synthesis, characterization and catalytic activity
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A series of diimines derived from saturated and unsaturated fatty acids and including a dipyridylamine (dpa) or a bispyridylmethane (bpm) scaffold as a chelating moiety were synthesized and characterized spectroscopically. Complexation by [LM(μ-Cl)Cl]sub
- Chevalley, Alice,Cherrier, Mickael V.,Fontecilla-Camps, Juan C.,Ghasemi, Mahsa,Salmain, Michele
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- Accessible Bifunctional Oxy-Tethered Ruthenium(II) Catalysts for Asymmetric Transfer Hydrogenation
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A concise synthesis of new oxy-tethered ruthenium complexes effective for the asymmetric transfer hydrogenation of aromatic ketones is described. The oxy-tether was constructed via a defluorinative etherification arising from an intramolecular nucleophilic substitution of a perfluorinated phenylsulfonyl substituent. The obtained tethered complexes exhibited desirable catalytic activity and selectivity, especially in the asymmetric transfer hydrogenation of functionalized aromatic ketones. The robustness and rigidity of the tether contribute to their superior catalytic performance relative to the nontethered prototype complex.
- Matsunami, Asuka,Ikeda, Marika,Nakamura, Hitomi,Yoshida, Minori,Kuwata, Shigeki,Kayaki, Yoshihito
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- Light-mediated regulation of asymmetric reduction of ketones by a cyanobacterium
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The stereochemical course of the asymmetric reduction of ketones by a photosynthetic microbe is largely regulated by light. Thus, we find that the enantioselectivity of the reduction of α,α-difluoroacetophenone with Synechococcus elongatus PCC 7942 increa
- Nakamura, Kaoru,Yamanaka, Rio
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- Effect of carbon dioxide concentrations on asymmetric reduction of ketones with plant-cultured cells
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Enantioselectivities in asymmetric reduction of ketones were controlled by atmospheric carbon dioxide concentrations: the reaction in high carbon dioxide concentrations under illumination of fluorescent light afforded the corresponding l-alcohol while tha
- Kojima, Hideo,Okada, Akiko,Takeda, Satomi,Nakamura, Kaoru
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- Synthesis of novel C2-symmetric chiral crown ethers and their application to enantioselective trifluoromethylation of aldehydes and ketones
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Synthesis of novel C2-symmetric chiral crown ethers and their application to enantioselective trifluoromethylation of aldehydes and ketones are discussed. The use of a series of C2-symmetric chiral crown ethers 2 or 3 derived from commercially available (R)-1,1′-bi-2-naphthol for the enantioselective trifluoromethylation of 2-naphthyl aldehyde 1a with (trifluoromethyl)trimethylsilane in the presence of a base was attempted. Iodo-substituted crown ether 2b was found to be the most effective in the model reaction. Moderate enantioselectivities were observed for the trifluoromethylation of both aryl or alkyl aldehydes and alkyl aryl ketones in 21-44% ees. Although the ees are still improvable, this is the first example of a chiral crown ether-catalyzed enantioselective trifluoromethylation reaction.
- Kawai, Hiroyuki,Kusuda, Akihiro,Mizuta, Satoshi,Nakamura, Shuichi,Funahashi, Yasuhiro,Masuda, Hideki,Shibata, Norio
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- Chemo- and Enantioselective Addition and β-Hydrogen Transfer Reduction of Carbonyl Compounds with Diethylzinc Reagent in One Pot Catalyzed by a Single Chiral Organometallic Catalyst
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Using a single chiral phosphoramide-Zn(II) complex as the catalyst, the asymmetric β-H transfer reduction of aromatic α-trifluoromethyl ketones and enantioselective addition of aromatic aldehydes with Et2Zn in one pot were successfully realized, affording the corresponding additive products of secondary alcohols in high yields (up to 99%) with excellent enantioselectivities (up to 98% ee) and the reduction products of α-trifluoromethyl alcohols in good to excellent yields with up to 77% ee.
- Huang, Huayin,Zong, Hua,Bian, Guangling,Song, Ling
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- First Enantioselective Hydrogenation of a Trifluoro-β-ketoester with Cinchona-Modified Platinum
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A series of trifluoromethyl ketones possessing different functional groups were hydrogenated over Pt/Al2O3 modified by cinchonidine and O-methylcinchonidine. The highest enantiomeric epcess of 90% was achieved in the hydrogenation of
- Von Arx,Mallat,Baiker
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- Assessment of headspace solid-phase microextraction (HS-SPME) for control of asymmetric bioreduction of ketones by Alternaria alternata
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The aim of this study was to assess the effectiveness of headspace solid-phase microextraction (HS-SPME) compared to liquid–liquid extractions using with methylene chloride (CH2Cl2) for control of fungal biotransformation of ketones of varying volatility. The proposed method was successfully applied. The best way to extract all the components of the mixture (alcohols, aldehydes) in quantities similar to the extraction of methylene chloride was the use of fibres coated with a combination of nonpolar material. SPME fibre assembly polydimethylsiloxane/divinylbenzene (PDMS/DVB) was most suitable for the extraction of the products mixture obtained after biotransformation of acetylcyclohexane and acetophenone. On the other hand, the best results were obtained for 2-acetylthiophene, α,α,α-trifluoroacetophenone and their derivatives using divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre. In addition, our study showed that Alternaria alternata is a good biocatalyst for bioreduction of ketones to alcohols according to Prelog's rule.
- Ogórek, Rafa?,Jarosz, Bogdan
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- Aqueous phase transfer hydrogenation of aryl ketones catalysed by achiral ruthenium(II) and rhodium(III) complexes and their papain conjugates
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Several ruthenium and rhodium complexes including 2,2-dipyridylamine ligands substituted at the central N atom by an alkyl chain terminated by a maleimide functional group were tested along with a newly synthesized Rh(III) complex of unsubstituted 2,2-dip
- Madern, Nathalie,Talbi, Barisa,Salmain, Michele
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- Magnetically separable Pt catalyst for asymmetric hydrogenation
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A magnetic Pt/SiO2/Fe3O4 catalyst consisting of chirally modified platinum supported on silica coated magnetite nanoparticles was prepared using an easy synthetic route and successfully applied for the enantioselective hydrogenation of various activated ketones. The magnetic catalyst modified with cinchonidine showed a catalytic performance (activity, enantioselectivity) in the asymmetric hydrogenation of various activated ketones in toluene comparable to the best known Pt/alumina catalyst used for these reactions. The novel catalyst can be easily separated from the reaction solution by applying an external magnetic field and recycled several times with almost complete retention of activity and enantioselectivity.
- Panella, Barbara,Vargas, Angelo,Baiker, Alfons
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- Novel access to N,N′-diaryl-trans-1,2-diaminocyclohexane ligands. A cheap and easy way to prepare ligand for asymmetric transfer hydrogenation
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N,N′-diaryl-trans-1,2-diaminocyclohexane ligands were prepared from 1,2-diaminocyclohexane and cyclohexanone derivatives via a heterogeneous palladium catalysis. In one step an alkylation followed by an aromatisation is performed under air or in the presence of an hydrogen trap. The interest of the synthesized ligands were evaluated in the reduction of aromatic ketones. The alcohols were efficiently and selectively obtained with an iridium complex and a mixture of formic acid and sodium formate.
- El-Asaad, Bilal,Guicheret, Boris,Métay, Estelle,Karamé, Iyad,Lemaire, Marc
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- Novel evidence on the role of the nucleophilic intermediate complex in the orito-reaction: Unexpected inversion in the enantioselective hydrogenation of 2,2,2-trifluoroacetophenone on Pt-Cinchona chiral catalyst using continuous-flow fixed-bed reactor
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The enantioselective hydrogenation of 2,2,2,- trifluoroacetophenone over Pt/Al2O3 catalysts modified by cinchona alkaloids was investigated for the first time using continuous-flow fixed-bed reactor system in toluene/AcOH 9/1 solvent
- Sz?ll?si, Gyo?rgy,Cserényi, Szabolcs,Bartók, Mihály
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- Abiotic reduction of ketones with silanes catalysed by carbonic anhydrase through an enzymatic zinc hydride
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Enzymatic reactions through mononuclear metal hydrides are unknown in nature, despite the prevalence of such intermediates in the reactions of synthetic transition-metal catalysts. If metalloenzymes could react through abiotic intermediates like these, then the scope of enzyme-catalysed reactions would expand. Here we show that zinc-containing carbonic anhydrase enzymes catalyse hydride transfers from silanes to ketones with high enantioselectivity. We report mechanistic data providing strong evidence that the process involves a mononuclear zinc hydride. This work shows that abiotic silanes can act as reducing equivalents in an enzyme-catalysed process and that monomeric hydrides of electropositive metals, which are typically unstable in protic environments, can be catalytic intermediates in enzymatic processes. Overall, this work bridges a gap between the types of transformation in molecular catalysis and biocatalysis. [Figure not available: see fulltext.]
- Ji, Pengfei,Park, Jeeyoung,Gu, Yang,Clark, Douglas S.,Hartwig, John F.
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(2021/02/26)
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- Asymmetric transfer hydrogenation of ketones promoted by manganese(I) pre-catalysts supported by bidentate aminophosphines
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A series of commercially available chiral amino-phosphines, in combination with Mn(CO)5Br, has been evaluated for the asymmetric reduction of ketones, using isopropanol as hydrogen source. With the most selective ligand, the corresponding manga
- Azouzi, Karim,Bruneau-Voisine, Antoine,Vendier, Laure,Sortais, Jean-Baptiste,Bastin, Stéphanie
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- Highly Enantioselective Transfer Hydrogenation of Prochiral Ketones Using Ru(II)-Chitosan Catalyst in Aqueous Media
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Unprecedentedly high enantioselectivities are obtained in the transfer hydrogenation of prochiral ketones catalyzed by a Ru complex formed in situ with chitosan chiral ligand. This biocompatible, biodegradable chiral polymer obtained from the natural chitin afforded good, up to 86 % enantioselectivities, in the aqueous-phase transfer hydrogenation of acetophenone derivatives using HCOONa as hydrogen donor. Cyclic ketones were transformed in even higher, over 90 %, enantioselectivities, whereas further increase, up to 97 %, was obtained in the transfer hydrogenations of heterocyclic ketones. The chiral catalyst precursor prepared ex situ was examined by scanning electron microscopy, FT-mid- and -far-IR spectroscopy. The structure of the in situ formed catalyst was investigated by 1H NMR spectroscopy and using various chitosan derivatives. It was shown that a Ru pre-catalyst is formed by coordination of the biopolymer to the metal by amino groups. This precursor is transformed in water insoluble Ru-hydride complex following hydrogen donor addition. The practical value of the developed method was verified by preparing over twenty chiral alcohols in good yields and optical purities. The catalyst was applied for obtaining optically pure chiral alcohols at gram scale following a single crystallization.
- Sz?ll?si, Gy?rgy,Kolcsár, Vanessza Judit
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p. 820 - 830
(2018/12/13)
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- Asymmetric Hydrogenation of Aryl Perfluoroalkyl Ketones Catalyzed by Rhodium(III) Monohydride Complexes Bearing Josiphos Ligands
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The asymmetric hydrogenation of 2,2,2-trifluoroacetophenones and aryl perfluoroalkyl ketones was developed using a unique, well-defined chloride-bridged dinuclear rhodium(III) complex bearing Josiphos-type diphosphine ligands. These complexes were prepared from [RhCl(cod)]2, Josiphos ligands, and hydrochloric acid. As catalyst precursors, they allow for the efficient and enantioselective synthesis (up to 99 % ee) of chiral secondary alcohols with perfluoroalkyl groups. This system does not require an activating base for the hydrogenation of 2,2,2-trifluoroacetophenones. Additionally, the enantioselective C=O hydrogenations of 2-phenyl-3-(haloacetyl)-indoles, a class of privileged structures in medicinal chemistry, is reported for the first time.
- Brüning, Fabian,Nagae, Haruki,K?ch, Daniel,Mashima, Kazushi,Togni, Antonio
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supporting information
p. 10818 - 10822
(2019/07/31)
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- Chemoenzymatic Synthesis of an Odanacatib Precursor through a Suzuki-Miyaura Cross-Coupling and Bioreduction Sequence
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A series of 1-aryl-2,2,2-trifluoroethanones has been chemically synthesized to later study their bioreduction using stereocomplementary alcohol dehydrogenases (ADHs). Satisfyingly, (R)-alcohols were obtained in high conversions and selectivities using the ADH from Ralstonia species and the one from Rhodococcus ruber, while the (S)-enantiomers were independently produced using the ADH from Lactobacillus brevis and the commercially available evo-1.1.200. In the search for a stereoselective route towards the Odanacatib, an orally bioavailable and selective inhibitor of Cathepsin K, the development of a sequential methodology combining a palladium-catalyzed cross coupling between 1-(4-bromophenyl)-2,2,2-trifluoroethanone and 4-(methylsulfonyl)phenylboronic acid in aqueous medium with the bioreduction of the resulting 2,2,2-trifluoro-1-(4′-(methylsulfonyl)-[1,1′-biphenyl]-4-yl)ethanone has been extensively studied. Finally, the desired (R)-2,2,2-trifluoro-1-(4′-(methylsulfonyl)-[1,1′-biphenyl]-4-yl)ethanol was obtained in enantiomerically pure form and 85 % yield with a 128 g L?1 d?1 productivity following a sequential approach.
- González-Martínez, Daniel,Gotor, Vicente,Gotor-Fernández, Vicente
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p. 5800 - 5807
(2019/11/05)
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- Proteins as Macromolecular Ligands for Metal-Catalysed Asymmetric Transfer Hydrogenation of Ketones in Aqueous Medium
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Biohybrid catalysts resulting from the dative anchoring of half-sandwich organometallic complexes [M(arene)(H2O)x(Cl)y]n+ (M = RuII, arene = η6-benzene, p-cymene or mesitylene; M = IrIII, RhIII, arene = η5-Cp*; x = 1–3, y = 0–2, n = 0–2) to bovine beta-lactoglobulin (βLG) or hen egg white lysozyme showed unprecedented behaviour. These constructs were shown to catalyse the asymmetric transfer hydrogenation of aryl ketones in water with sodium formate as hydrogen donor at a much faster rate than the complexes alone. Full conversion of the benchmark substrate 2,2,2-trifluoroacetophenone was reached with an ee of 86 % for the most selective biohybrid. Surprisingly, even the crude biohybrid gave a good ee despite the presence of non-protein-bound metal species in the reaction medium. Other aryl ketones were reduced in the same way, and the highest ee was obtained for ortho-substituted acetophenone derivatives. Furthermore, treatment of βLG with dimethyl pyrocarbonate resulted in a noticeable decrease of the activity and selectivity of the biohybrid, indicating that the sole accessible histidine residue (His146) was probably involved in the coordination and activation of Ru(benzene). This work underscores that protein scaffolds are efficient chiral ligands for asymmetric catalysis. The use of sodium formate instead of dihydrogen makes this approach safe, inexpensive and environmentally friendly.
- de Jesús Cázares-Marinero, José,Przybylski, Cédric,Salmain, Michèle
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p. 1383 - 1393
(2018/04/06)
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- Molecular Basis for the High Activity and Enantioselectivity of the Carbonyl Reductase from Sporobolomyces salmonicolor toward α-Haloacetophenones
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In an effort to develop a practical method for the synthesis of optically pure 2,2,2-trifluoro-1-phenylethanol, we found that the carbonyl reductase (SSCR) from Sporobolomyces salmonicolor showed excellent activity and enantioselectivity toward the halogenated acetophenones. Especially, SSCR exhibited more than 1000 times higher activity toward α,α,α-trifluoroacetophenone than unsubstituted acetophenone, a strikingly different observation from the previously well-studied alcohol dehydrogenase (LBADH) from Lactobacillus brevis. Enzyme-substrate docking and site-directed mutagenesis studies revealed the molecular basis for the high enzyme activity and enantioselectivity of SSCR toward the α-halogenated acetophenones. The hydrogen bond of the Asn207 side chain with the substrate halogen atom and the XH/π interaction of the substrate phenyl group with the side chains of Ser222/Thr223 resulted in the formation of the highly reactive conformation of α-halogenated acetophenones in the active site of the enzyme. (S)-2,2,2-Trifluoro-1-phenylethanol was prepared in excellent isolated yield and enantiomeric excess from the reduction of α,α,α-trifluoroacetophenone with mutant T209A. These results suggest that tuning the interactions between the halogen atoms/phenyl group of the substrate and the amino acid residues of the enzyme would lead to valuable mutants for the practical synthesis of β-haloalcohols.
- Chen, Xi,Zhang, Hongliu,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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p. 3525 - 3531
(2018/04/14)
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- HEME PROTEIN CATALYSTS FOR CARBON-BORON BOND FORMATION IN VITRO AND IN VIVO
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Provided herein are methods for producing an organoboron product. The methods include combining a boron-containing reagent and a carbene precursor in the presence of a heme protein, e.g., a cytochrome c, a cytochrome P450, a globin, a protoglobin, a nitric oxide dioxygenase, a peroxidase, or a catalase, or a variant thereof, under conditions sufficient to form the organoboron product. Reaction mixtures for producing organoboron products are also described, as well as whole-cell catalysts comprising heme proteins and variants thereof for forming carbon-boron bonds.
- -
-
Paragraph 0028; 0267; 0269
(2018/09/28)
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- Synthesis of new C3 symmetric amino acid- and aminoalcohol-containing chiral stationary phases and application to HPLC enantioseparations
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We recently reported a new C3-symmetric (R)-phenylglycinol N-1,3,5-benzenetricarboxylic acid-derived chiral high-performance liquid chromatography (HPLC) stationary phase (CSP 1) that demonstrated better results as compared to a previously described N-3,5-dintrobenzoyl (DNB) (R)-phenylglycinol-derived CSP. Over a decade ago, (S)-leucinol, (R)-phenylglycine, and (S)-leucine derivatives were used as the starting materials of 3,5-DNB-based Pirkle-type CSPs for chiral separation. In this study, three new C3-symmetric CSPs (CSP 2, 3, and 4) were prepared by combining the ideas and results mentioned above. Here we describe the synthetic procedures and applications of the new C3-symmetric CSPs (CSP 2–CSP 4).
- Yu, Jeongjae,Armstrong, Daniel W.,Ryoo, Jae Jeong
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- Acylative Kinetic Resolution of Alcohols Using a Recyclable Polymer-Supported Isothiourea Catalyst in Batch and Flow
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A polystyrene-supported isothiourea catalyst, based on the homogeneous catalyst HyperBTM, has been prepared and used for the acylative kinetic resolution of secondary alcohols. A wide range of alcohols, including benzylic, allylic, and propargylic alcohols, cycloalkanol derivatives, and a 1,2-diol, has been resolved using either propionic or isobutyric anhydride with good to excellent selectivity factors obtained (28 examples, s values up to 600). The catalyst can be recovered and reused by a simple filtration and washing sequence, with no special precautions needed. The recyclability of the catalyst was demonstrated (15 cycles) with no significant loss in either activity or selectivity. The recyclable catalyst was also used for the sequential resolution of 10 different alcohols using different anhydrides with no cross-contamination between cycles. Finally, successful application in a continuous flow process demonstrated the first example of an immobilized Lewis base catalyst used for the kinetic resolution of alcohols in flow.
- Neyyappadath, Rifahath Mon,Chisholm, Ross,Greenhalgh, Mark D.,Rodríguez-Escrich, Carles,Pericàs, Miquel A.,H?hner, Georg,Smith, Andrew D.
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p. 1067 - 1075
(2018/02/14)
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- Efficient Synthesis of (R)-2-Chloro-1-(2,4-dichlorophenyl)ethanol with a Ketoreductase from Scheffersomyces stipitis CBS 6045
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By enzyme screening, a ketoreductase cloned from Scheffersomyces stipitis CBS 6045 and named SsCR was identified that could catalyze the asymmetric hydrogenation of a variety of aromatic ketones. SsCR exhibited a specific activity of 65 U mg?1p
- Shang, Yue-Peng,Chen, Qi,Kong, Xu-Dong,Zhang, Yu-Jun,Xu, Jian-He,Yu, Hui-Lei
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supporting information
p. 426 - 431
(2017/02/10)
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- Catalytic asymmetric Meerwein-Ponndorf-Verley reduction of glyoxylates induced by a chiral N,N′-dioxide/Y(OTf)3 complex
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An asymmetric Meerwein-Ponndorf-Verley (MPV) reduction of glyoxylates was for the first time accomplished via an N,N′-dioxide/Y(OTf)3 complex with aluminium alkoxide and molecular sieves (MSs) as crucial additives. A variety of optically active α-hydroxyesters were obtained with excellent results. A possible reaction mechanism was proposed based on the experiments.
- Wu, Wangbin,Zou, Sijia,Lin, Lili,Ji, Jie,Zhang, Yuheng,Ma, Baiwei,Liu, Xiaohua,Feng, Xiaoming
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supporting information
p. 3232 - 3235
(2017/03/20)
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- Synthetically useful variants of industrial lipases from: Burkholderia cepacia and Pseudomonas fluorescens
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Industrial enzymes lipase PS (LPS) and lipase AK (LAK), which originate from Burkholderia cepacia and Pseudomonas fluorescens, respectively, are synthetically useful biocatalysts. To strengthen their catalytic performances, we introduced two mutations into hot spots of the active sites (residues 287 and 290). The LPS-L287F/I290A double mutant showed high catalytic activity and enantioselectivity for poor substrates for which the wild-type enzyme showed very low activity. The LAK-V287F/I290A double mutant was also an excellent biocatalyst with expanded substrate scope, which was comparable to the LPS-L287F/I290A double mutant. Thermodynamic parameters were determined to address the origin of the high enantioselectivity of the double mutant. The ΔΔH? term, but not the ΔΔS? term, was predominant, which suggests that the enantioselectivity is driven by a differential energy associated with intermolecular interactions around Phe287 and Ala290. A remarkable solvent effect was observed, giving a bell-shaped profile between the E values and the log&P or ? values of solvents with the highest E value in i-Pr2O. This suggests that an organic solvent with appropriate hydrophobicity and polarity provides the double mutant with some flexibility that is essential for excellent catalytic performance.
- Yoshida, Kazunori,Ono, Masakazu,Yamamoto, Takahiro,Utsumi, Takashi,Koikeda, Satoshi,Ema, Tadashi
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supporting information
p. 8713 - 8719
(2017/11/03)
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- Fine tuning of molecular and supramolecular properties of simple trianglimines-the role of the functional group
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Chiral, triangular poly-azamacrocycles (trianglimines) readily available from enantiomerically pure trans-1,2-diaminocyclohexane and various aromatic dialdehydes, differ in their nature and substitution pattern. The highly symmetrical macrocycle having two electron-donating groups attached to the aryl moieties is formed under thermodynamic control that fulfilled the so called entropy of symmetry rule. Conversely, from the 2-nitroterephthaldehyde a kinetic product of trivial C1 symmetry is solely obtained, whereas from 2-methoxyterepthaldehyde a mixture of C3- and C1-symmetrical macrocycles are formed. The factors that contribute to the mechanism of the macrocycle formation were determined on the basis of an experimental/theoretical approach. The non-symmetrical structure of the macrocycle resulted from a symmetrical intermediate that appeared during cyclocondensation. The chiroptical properties of the trianglimines were studied by means of experimental ECD and VCD methods supported by quantum-chemical calculations. The nitro-substituted trianglimine appeared to be a simple, low molecular weight supergelator forming in polar media of stable chiral organogels. The structure of the gel is affected by the nature and chirality of the dopant. The hexaimine macrocycles after reduction of the CN imine bonds formed trianglamines-useful chiral ligands in stereoselective synthesis. The Zn-trianglamine complexes were employed as catalysts for asymmetric hydrosilylation of prochiral ketones, providing products of enantiomeric excess up to 98%. This remains the best result obtained for Zn-diamine catalysed asymmetric hydrosilylation of ketones so far.
- Gajewy,Szymkowiak,Kwit
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p. 53358 - 53369
(2016/06/14)
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- A series of novel β-hydroxyamide based catalysts for borane-mediated enantioselective reductions of prochiral ketones: Dedicated to Professor Halil Hosgoren on the occasion of his 66th birthday
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The enantioselective reduction of prochiral ketones with borane in the presence of a chiral ligand has received considerable attention. Hydroxylamine-based chiral ligands with amide and hydroxyl functions in the presence of other co-ordinating groups are highly effective in these asymmetric reductions. The current work presents a simple one step synthesis of a series of β-hydroxyamide-based ligands from the reaction between 3-hydroxy-2-naphthoic acid and chiral amino alcohols and their applications as catalysts in asymmetric borane-mediated reductions of aromatic prochiral ketones in THF. The reductions provided the corresponding secondary alcohols with up to 96% ee and in good to excellent yields (89–99%). DFT calculations at B3LYP/6-31+g(d) level offered theoretical models to account for the enantioselectivity imposed by the chiral ligands in the reductions of the ketones.
- Azizoglu, Murat,Erdogan, Asl?,Arslan, Nevin,Turgut, Y?lmaz,Hosgoren, Halil,Pirinccioglu, Necmettin
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p. 614 - 622
(2016/07/12)
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- Third-Generation Amino Acid Furanoside-Based Ligands from d-Mannose for the Asymmetric Transfer Hydrogenation of Ketones: Catalysts with an Exceptionally Wide Substrate Scope
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A modular ligand library of α-amino acid hydroxyamides and thioamides was prepared from 10 different N-tert-butyloxycarbonyl-protected α-amino acids and three different amino alcohols derived from 2,3-O-isopropylidene-α-d-mannofuranoside. The ligand library was evaluated in the half-sandwich ruthenium- and rhodium-catalyzed asymmetric transfer hydrogenation of a wide array of ketone substrates, including simple as well as sterically demanding aryl alkyl ketones, aryl fluoroalkyl ketones, heteroaromatic alkyl ketones, aliphatic, conjugated and propargylic ketones. Under the optimized reaction conditions, secondary alcohols were obtained in high yields and in enantioselectivities up to >99%. The choice of ligand/catalyst allowed for the generation of both enantiomers of the secondary alcohols, where the ruthenium-hydroxyamide and the rhodium-thioamide catalysts act complementarily towards each other. The catalytic systems were also evaluated in the tandem isomerization/asymmetric transfer hydrogenation of racemic allylic alcohols to yield enantiomerically enriched saturated secondary alcohols in up to 98% ee. Furthermore, the catalytic tandem α-alkylation/asymmetric transfer hydrogenation of acetophenones and 3-acetylpyridine with primary alcohols as alkylating and reducing agents was studied. Secondary alcohols containing an elongated alkyl chain were obtained in up to 92% ee. (Figure presented.).
- Margalef, Jèssica,Slagbrand, Tove,Tinnis, Fredrik,Adolfsson, Hans,Diéguez, Montserrat,Pàmies, Oscar
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p. 4006 - 4018
(2016/12/30)
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- Preparation of enantiomerically enriched aromatic β-hydroxynitriles and halohydrins by ketone reduction with recombinant ketoreductase KRED1-Pglu
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A NADPH-dependent benzil reductase (KRED1-Pglu) was used as recombinant enzyme for catalysing the reduction of different functionalised ketones. The reactions were carried out in the presence of a catalytic amount of NADP+and an enzyme-coupled transformation (oxidation of glucose catalysed by glucose dehydrogenase), for regenerating the cofactor and thus driving the reaction to completion. KRED1-Pglu showed remarkable versatility, being able to reduce different β-ketonitriles and α-haloketones at different pHs; notably, depending on the nature of the substrate, KRED1-Pglu can be used for efficient and clean enzymatic reduction, avoiding side-reactions due to the pH of the medium. The reduction generally occurred with high enantioselectivity, allowing the preparation of enantiomerically enriched β-hydroxynitriles and halohydrins in high yields; the stereochemical outcome of the reduction followed in all the cases the so-called Prelog's rule.
- Contente, Martina L.,Serra, Immacolata,Molinari, Francesco,Gandolfi, Raffaella,Pinto, Andrea,Romano, Diego
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p. 3974 - 3979
(2016/07/06)
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- Chiral terpene auxiliaries III: Spiroborate esters from (1R,2S,3R,5R)-3-amino-apopinan-2-ol as highly effective catalysts for asymmetric reduction of ketones with borane
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New spiroborate esters, derived from terpene amino alcohols, (S)-prolinol, and 2-aminoethanol, were employed as catalysts in the borane reduction of acetophenone and other aryl alkyl and halogenated ketones. The corresponding alcohols were obtained in high yields and with enantioselectivities up to 98% ee. The influence of the amino alcohol and the diol moieties of spiroborate on the reaction selectivity was examined. The catalyst load, the nature of the solvent, the borane source, and the reaction conditions were also investigated.
- ?wiklińska, Marta,Krzemiński, Marek P.,Tafelska-Kaczmarek, Agnieszka
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p. 1453 - 1458
(2015/12/09)
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- Identification of an ε-keto ester reductase for the efficient synthesis of an (R)-α-lipoic acid precursor
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Abstract A novel reductase (CpAR2) with unusually high activity toward an ε-keto ester, ethyl 8-chloro-6-oxooctanoate, was isolated from Candida parapsilosis. The asymmetric reduction of ethyl 8-chloro-6-oxooctanoate using Escherichia coli cells coexpressing CpAR2 and glucose dehydrogenase genes gave ethyl (R)-8-chloro-6-hydroxyoctanoate, a key precursor for the synthesis of (R)-α-lipoic acid, in high space-time yield (530 gL-1d-1) and with excellent enantiomeric excess (>99%). This bioprocess was shown to be viable on a 10-L scale. This method provides a greener and more cost-effective method for the industrial production of (R)-α-lipoic acid.
- Zhang, Yu-Jun,Zhang, Wen-Xia,Zheng, Gao-Wei,Xu, Jian-He
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supporting information
p. 1697 - 1702
(2015/06/02)
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- Modular hydroxyamide and thioamide pyranoside-based ligand library from the sugar pool: New class of ligands for asymmetric transfer hydrogenation of ketones
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A large library of pyranoside-based hydroxyamide and thioamide ligands has been synthesized for asymmetric transfer hydrogenation in an attempt to expand the scope of the substrates to cover a broader range of challenging heteroaromatic and aryl/fluoroalkyl ketones. These ligands have the advantage that they are prepared from commercial D-glucose, D-glucosamine and α-amino acids, inexpensive natural chiral feedstocks. By carefully selecting the ligand components (substituents/configurations at the amide/thioamide moiety, the position of amide/thioamide group and the configuration at C-2), we found that pyranoside-based thioamide ligands provided excellent enantioselectivities (in the best cases, ees of >99% were achieved) in a broad range of ketones, including the less studied heteroaromatics and challenging aryl/fluoroalkyls. Note that both enantiomers of the reduction products can be obtained with excellent enantioselectivities by simply changing the absolute configuration of the thioamide substituent.
- Coll, Mercè,Pàmies, Oscar,Diéguez, Montserrat
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p. 2293 - 2302
(2014/07/21)
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- Synthesis and catalytic applications of an extended range of tethered ruthenium(II)/η6-arene/diamine complexes
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A series of novel enantiopure Ru(II) complexes containing a chiral diamine and η6-arene connected by a tethering group have been prepared and were evaluated in the asymmetric reductions of a range of ketones. Changes to the level of steric hindrance and the addition of an electron-withdrawing functionality on the sulfonyl group have a significant effect on the reactivity and enantioselectivity of the catalysts.
- Hodgkinson, Roy,Jurk, Vclav,Zanotti-Gerosa, Antonio,Nedden, Hans Günter,Blackaby, Andrew,Clarkson, Guy J.,Wills, Martin
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supporting information
p. 5517 - 5524
(2015/02/19)
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- Iron catalyzed asymmetric hydrogenation of ketones
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Chiral molecules, such as alcohols, are vital for the manufacturing of fine chemicals, pharmaceuticals, agrochemicals, fragrances, and novel materials. These molecules need to be produced in high yield and high optical purity and preferentially catalytically. Among all the asymmetric catalytic reactions, asymmetric hydrogenation with H2 (AH) is the most widely used in the industry. With few exceptions, these AH processes use catalysts based on the three critical metals, rhodium, ruthenium, and iridium. Herein we describe a simple, industrially viable iron catalyst that allows for the AH of ketones, a process currently dominated by ruthenium and rhodium catalysts. By combining a chiral, 22-membered macrocyclic ligand with the cheap, readily available Fe 3(CO)12, a wide variety of ketones have been hydrogenated under 50 bar H2 at 45-65 C, affording highly valuable chiral alcohols with enantioselectivities approaching or surpassing those obtained with the noble metal catalysts. In contrast to AH by most noble metal catalysts, the iron-catalyzed hydrogenation appears to be heterogeneous.
- Li, Yanyun,Yu, Shenluan,Wu, Xiaofeng,Xiao, Jianliang,Shen, Weiyi,Dong, Zhenrong,Gao, Jingxing
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supporting information
p. 4031 - 4039
(2014/04/03)
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- β-Hydroxyamide derivatives of salicylic acid as organocatalysts for enantioselective reductions of prochiral ketones
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In order to find the most effective catalyst for the enantioselective reduction of a prochiral ketone, a series of novel β-hydroxyamide derivatives of salicylic acid and chiral amino alcohols were synthesized. Different substituted prochiral ketones have been reduced in high yield (up to 99%) and the corresponding secondary alcohols are formed with good enantiomeric excess (up to 86%). The mechanism of this type of catalyst can be explained by considering the reaction mechanism for the CBS catalyst.
- Turgut, Yilmaz,Azizoglu, Murat,Erdogan, Asli,Arslan, Nevin,Hosgoren, Halil
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p. 853 - 859
(2013/08/23)
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- Biphasic glycerol/2-MeTHF, ruthenium-catalysed enantioselective transfer hydrogenation of ketones using sodium hypophosphite as hydrogen donor
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Sodium hypophosphite has been used as an efficient hydrogen donor in the transfer hydrogenation of aliphatic and aromatic ketones in the presence of [RuCl2(p-cymene)]2 and 2,2′-bipyridine in water. The corresponding alcohols were isolated in moderate to excellent yields (39-95 %). Good chemoselectivity was observed with ester, nitrile and halide functionalities in the ketones not being reduced. An enantioselective version of the reaction using [RuCl(p-cymene){(R,R)-TsDPEN}] as catalyst in a glycerol/2-MeTHF biphasic solvent mixture has been developed and allowed the reduction of (hetero)aromatic ketones with excellent chemo- and enantioselectivities (up to 97 % ee). Sodium hypophosphite has been used in the reduction of ketones in water (nine examples, 40-95 % yield). An original glycerol/2-MeTHF biphasic solvent system has been developed for the enantioselective version of the reaction. This system allows the preparation of aryl alkyl alcohols with up to 97 % ee (22 examples). Copyright
- Guyon, Carole,Metay, Estelle,Duguet, Nicolas,Lemaire, Marc
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supporting information
p. 5439 - 5444
(2013/09/02)
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- Synthesis of enantiopure fluorohydrins using alcohol dehydrogenases at high substrate concentrations
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The use of purified and overexpressed alcohol dehydrogenases to synthesize enantiopure fluorinated alcohols is shown. When the bioreductions were performed with ADH-A from Rhodococcus ruber overexpressed in E. coli, no external cofactor was necessary to obtain the enantiopure (R)-derivatives. Employing Lactobacillus brevis ADH, it was possible to achieve the synthesis of enantiopure (S)-fluorohydrins at a 0.5 M substrate concentration. Furthermore, due to the activated character of these substrates, a huge excess of the hydrogen donor was not necessary.
- Borzeicka, Wioleta,Lavandera, Ivan,Gotor, Vicente
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p. 7312 - 7317
(2013/08/23)
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- Enzymatic resolution by CALB of organofluorine compounds under conventional condition and microwave irradiation
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Enzymatic kinetic resolution of organofluorine rac-alcohols by CALB yielded ( )-(R)-2,2,2-trifluoro-1- phenylethanol (2a), ()-(R)-1-(3-bromophenyl)-2,2,2- trifluoroethanol (2b), ()-(R)-1-(4-bromophenyl)- 2,2,2-trifluoroethanol (2c), ()-(S)-1-(2,4,5-trifluorophenyl)ethanol (2d), (+)-(S)-2,2,2-trifluoro-1- phenylethyl acetate (3a), (+)-(S)-1-(3-bromophenyl)-2,2,2-trifluoroethyl acetate (3b), (+)-(S)-1-(4- bromophenyl)-2,2,2-trifluoroethyl acetate (3c) and (+)-(R)-1-(2,4,5-trifluorophenyl)ethyl acetate (3d) in high enantiomeric excess (up to >99% ee). The reactions were conducted under conventional conditions (orbital shaking) and microwave irradiation in toluene and vinyl acetate as acylating agent. The CALB showed excellent selectivities and good yields in the transesterification of fluorinated aromatic compounds.
- Ribeiro, Sandra S.,Raminelli, Cristiano,Porto, André L.M.
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- The enantioselective trifluoromethylation of aromatic aldehydes by quaternary ammonium bromide and (IPr)CuF at low catalyst loading
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A general catalytic enantioselective trifluoromethylation of aromatic aldehydes using (IPr)CuF and quinidine-derived quaternary ammonium salt as catalysts has been developed. A wide range of aromatic aldehydes are converted to the corresponding products in up to 92% yield and 81% ee at 2 mol% of catalyst loading.
- Wu, Shaoxiang,Guo, Jiyi,Sohail, Muhammad,Cao, Chengyao,Chen, Fu-Xue
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- Stereospecific reduction of methyl o-chlorobenzoylformate at 300 g·L-1 without additional cofactor using a carbonyl reductase mined from Candida glabrata
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In order to search for oxidoreductases suitable for the preparation of methyl (R)-o-chloromandelate [(R)-CMM], the key intermediate for clopidogrel, the homologous proteins of Gre2p were expressed in Escherichia coli, among which CgKR1 showed the most satisfactory activity and stereoselectivity towards methyl o-chlorobenzoylformate (CBFM). Using the crude enzyme of CgKR1 and glucose dehydrogenase (GDH), as much as 300 g·L-1 of CBFM was almost stoichiometrically converted to (R)-CMM with excellent enantiomeric excess (98.7% ee). More importantly, the reaction could be performed without external addition of an expensive cofactor. The substrate profile indicates that keto esters serve as the most suitable substrate, which was confirmed by gram-scale preparations. Homology modeling and docking analysis revealed the molecular basis for the high stereoselectivity of CgKR1. These demonstrate not only the feasibility of in silico mining of novel enzymes based on sequence homology but also the applicability of this new reductase for the practical production of optically active (R)-CMM. Copyright
- Ma, Hongmin,Yang, Linlin,Ni, Yan,Zhang, Jie,Li, Chun-Xiu,Zheng, Gao-Wei,Yang, Huaiyu,Xu, Jian-He
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experimental part
p. 1765 - 1772
(2012/08/08)
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