- Asymmetric transfer hydrogenation of ketonic substrates catalyzed by (η5-C5Me5)MCl complexes (M = Rh and Ir) of (1S, 2S)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine
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The rhodium and iridium (η5-C5Me5)MCl complexes (3a: M = Rh; 3b: M = Ir) of (1S,25)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine were found to be catalyst precursors for asymmetric transfer hydrogenation of acetophenone, 2-acetonaphthone, 1-tetralone, and 1-indanone to give (S)-1-phenylethanol (90% ee), (S)-1-(2-naphthyl)ethanol (85% ee), (S)-1-tetralol (97% ee), and (S)-indanol (99% ee), respectively.
- Mashima, Kazushi,Abe, Tomoyuki,Tani, Kazuhide
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Read Online
- Asymmetric Aggregative Activation. A New Useful Concept for Asymmetric Reduction
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Reduction of arylketones with a Complex Reducing Agent containing 2 equivalents of Zn0 and 4 equivalents of sodium chiraldate in a mixture of THF and methylcyclohexane for 1 equivalent of arylketone took place with a chiral induction from 56 to 89 percent of enantiomeric excess.
- Lalloz, Lucien,Vanderesse, Regis,Mayesky, Bertrand,Caubere, Paul
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Read Online
- Designer Outer Membrane Protein Facilitates Uptake of Decoy Molecules into a Cytochrome P450BM3-Based Whole-Cell Biocatalyst
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We report an OmpF loop deletion mutant, which improves the cellular uptake of external additives into an Escherichia coli whole-cell biocatalyst. Through co-expression of the OmpF mutant with wild-type P450BM3 in the presence of decoy molecules, the yield
- Karasawa, Masayuki,Shoji, Osami,Stanfield, Joshua Kyle,Suzuki, Kazuto,Yonemura, Kai
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supporting information
(2021/12/16)
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- Cobalt-catalyzed asymmetric hydrogenation of ketones: A remarkable additive effect on enantioselectivity
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A chiral cobalt pincer complex, when combined with an achiral electron-rich mono-phosphine ligand, catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones, affording chiral alcohols with high yields and moderate to excellent enantioselectivities (29 examples, up to 93% ee). Notably, the achiral mono-phosphine ligand shows a remarkable effect on the enantioselectivity of the reaction.
- Du, Tian,Wang, Biwen,Wang, Chao,Xiao, Jianliang,Tang, Weijun
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supporting information
p. 1241 - 1244
(2020/10/02)
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- Biocatalytic asymmetric synthesis of (S)-1-indanol using Lactobacillus paracasei BD71
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Enantiopure benzo-fused cyclic alcohols have been used as a building block of a drug for Parkinson’s disease. Biocatalytic reduction of ketones is one of the most promising and significant routes to prepare optically active alcohols. In this study, the reductive capacity of seven lactic acid bacteria (LAB) strains were investigated as whole-cell biocatalyst in the enantioselective reduction of 1-indanone (1). Lactobacillus paracasei BD71 was found to have the best reductive capacity. Effects of different parameters such as pH, incubation time, agitation speed and temperature, on enantiomeric excess (ee) and conversion were investigated in a bioconversion. (S)-1-indanol ((S)-2) could be used as precursor for the synthesis of rasagiline mesylate TVP1012 for the therapy of Parkinson’s illness. It was produced in gram-scale (5.24 g), high yield (93%) and enantiomerically pure form using L. paracasei BD71 whole-cell biocatalysts. Also, to our knowledge, this is the first report on production of (S)-2 using whole-cell catalyst in enantiopure form, excellent yield, conversion and gram scale. This is a cheap, clean and eco-friendly process for production of (S)-2 compared to chemical processes.
- ?ahin, Engin,Dertli, Enes,Kalay, Erbay
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- Supramolecular chiral electrochemical reduction of acetophenone with hybridization of a chiral multifarene and Au nanoparticles
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A supramolecular chiral electrode was constructed by layer-by-layer assembly of gold nanoparticles (AuNPs) and an S-chiral multifarene [3,2,1] (S-CMF) on the surface of a glassy carbon electrode, which was applied for the electroreduction of acetophenone. The host-guest encapsulation of the substrate within the chiral cavity was confirmed by 1H NMR, fluorescence titration, and molecular simulation. The composite on the electrode surface was characterized by electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM). Optimization of the electrolysis process was performed to give a high yield of 70.9% and high enantioselectivity of 63.9% ee, which exhibited superior reactivity to the previously reported materials. The repeatability of the experiment was tested via five separate experiments and indicated consistent stability, recyclability, and reusability of the novel chiral electrode. The proposed mechanism involved supramolecular encapsulation, two single-electron transfer steps, and proton addition. The chiral electroorganic reduction was extended to more substrates to provide successful yields and enantioselectivity.
- Cong, Hang,Ge, Qingmei,Li, Heng,Liu, Mao,Tao, Zhu,Xue, Yan-Fang
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p. 529 - 536
(2021/11/20)
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- Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
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A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
- Oestreich, Martin,Seliger, Jan
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p. 247 - 251
(2020/10/29)
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- Homochiral Dodecanuclear Lanthanide "cage in Cage" for Enantioselective Separation
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It is extremely difficult to anticipate the structure and the stereochemistry of a complex, particularly when the ligand is flexible and the metal node adopts diverse coordination numbers. When trivalent lanthanides (LnIII) and enantiopure amino acid ligands are utilized as building blocks, self-assembly sometimes yields rare chiral polynuclear structures. In this study, an enantiopure carboxyl-functionalized amino acid-based ligand with C3 symmetry reacts with lanthanum cations to give a homochiral porous coordination cage, (Δ/λ)12-PCC-57. The dodecanuclear lanthanide cage has an unprecedented octahedral "cage-in-cage"framework. During the self-assembly, the chirality is transferred from the enantiopure ligand and fixed by the binuclear lanthanide cluster to give 12 metal centers that have either Δor λ homochiral stereochemistry. The cage exhibits excellent enantioselective separation of racemic alcohols, 2,3-dihydroquinazolinones, and multiple commercially available drugs. This finding exhibits a rare example of a multinuclear lanthanide complex with a dual-walled topology and homochirality. The highly ordered self-assembly and self-sorting of flexible amino acids and lanthanides shed light on the chiral transformation between different complicated artificial systems that mimic natural enzymes.
- Zhu, Chengfeng,Tang, Haitong,Yang, Keke,Fang, Yu,Wang, Kun-Yu,Xiao, Zhifeng,Wu, Xiang,Li, Yougui,Powell, Joshua A.,Zhou, Hong-Cai
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supporting information
p. 12560 - 12566
(2021/08/23)
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- C3 The symmetry contains a chiral ligand H3L of an amide bond. Preparation method and application
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The invention discloses C. 3 Chiral ligand H with symmetric amide bond3 L Relates to the technical field of material chemistry and chiral chemistry. The invention further provides the chiral ligand H. 3 L Preparation method and application thereof. The present invention has the advantage that the chiral ligand H of the present invention is a chiral ligand. 3 The L has a higher C. 3 The symmetric and flexible amide group enables coordination of the lanthanide metal ions with high coordination number and high oxygen affinity to be assembled into a novel structure-structure lanthanide metal chiral porous coordination cage. Moreover, the abundant chiral amide groups and amino acid residues on the ligand framework can be directly introduced into the synthesized lanthanide metal chiral porous coordination cage, thereby being beneficial to generating multiple chiral recognition sites and unique chiral microenvironments which mimic the biological enzyme binding pocket and further realize the purpose of high enantioselectivity separation of a series of chiral small molecule compounds.
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Paragraph 0092-0100
(2021/09/08)
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- Chiral salen - Ni (II) based spherical porous silica as platform for asymmetric transfer hydrogenation reaction and synthesis of potent drug intermediate montekulast
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Heterogeneous catalyst has an edge over homogeneous systems in terms of recyclability, activity, stability and recovery. Silica has evolved as a good support material in heterogeneous systems due to its stability and ability to get modified as per the end application. Herein, we report a novel chiral Ni-Schiff base derived catalyst and its immobilization into mesoporous silica which was synthesized by post-grafting process. The chiral catalyst demonstrated remarkably high catalytic activity, enantioselectivity (up to 99 % enantiomers excess) for heterogeneous asymmetric transfer hydrogenation of various ketones. The developed catalyst was characterized by Ultraviolet-visible spectroscopy (UV–vis), Fourier-Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET isotherm), Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDX), High Resolution – Transmission Electron Microscopy (HR-TEM), Vibrating Sample Magnetometer (VSM), X-ray Photoelectron Spectroscopy (XPS) and elemental analysis. The catalyst could be recovered and reused for multiple consecutive runs without losing the enantioselectivity. The chiral catalyst was used in asymmetric transfer hydrogenation reaction for synthesizing enantiomerically pure drug intermediate Montekulast.
- Shukla, Meenakshi,Barick,Salunke,Chandra, Sudeshna
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- Enantioselective direct, base-free hydrogenation of ketones by a manganese amido complex of a homochiral, unsymmetrical P-N-P′ ligand
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The use of manganese in homogeneous hydrogenation catalysis has been a recent focus in the pursuit of more environmentally benign base metal catalysts. It has great promise with its unique reactivity when coupled with metal-ligand cooperation of aminophosphine pincer ligands. Here, a manganese precatalyst Mn(P-N-P′)(CO)2, where P-N-P′ is the amido form of the ligand (S,S)-PPh2CHPhCHPhNHCH2CH2PiPr2, has been synthesized and used for base-free ketone hydrogenation. This catalyst shows exceptionally high enantioselectivity and good activity, with tolerance for base-sensitive substrates. NMR structural analysis of intermediates formed by the reaction of the amido complex with hydrogen under pressure identified a reactive hydride with an NOE contact with the syn amine proton. Computational analysis of the catalytic cycle reveals that the heterolytic splitting of dihydrogen across the MnN bond in the amido complex has a low barrier while the hydride transfer to the ketone is the turnover-limiting step. The pro-S transition state is found to be usually much lower in energy than the pro-R transition state depending on the ketone structure, consistent with the high (S) enantiomeric excess in the alcohol products. The energy to reach the transition state is higher for the distortion of the in-coming ketone than that of the hydride complex. In a one-to-one comparison with the similar iron catalyst FeH2(CO)(P-NH-P′), the manganese catalyst is found to have higher enantioselectivity, often over 95% ee, while the iron catalyst has higher activity and productivity. An explanation of these differences is provided on the basis of the more deformable iron hydride complex due to the smaller hydride ligands.
- Seo, Chris S. G.,Tsui, Brian T. H.,Gradiski, Matthew V.,Smith, Samantha A. M.,Morris, Robert H.
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p. 3153 - 3163
(2021/05/25)
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- Chiral Yolk-Shell MOF as an Efficient Nanoreactor for Asymmetric Catalysis in Organic-Aqueous Two-Phase System
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It remains a great challenge to introduce large and efficient homogeneous asymmetric catalysts into MOFs and other microporous materials as well as retain their degrees of freedom. Herein, a new heterogeneous strategy of homogeneous chiral catalysts is proposed, that is, to construct a yolk-shell MOFs-confined, large-size, and highly efficient homogeneous chiral catalyst, which can be used as a nanoreactor for asymmetric catalytic reactions.
- Shi, Shunli,Zhong, Yicheng,Hu, Zhuo,Wang, Lei,Yuan, Mingwei,Ding, Shunmin,Wang, Shuhua,Chen, Chao
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supporting information
p. 12714 - 12718
(2021/09/11)
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- Enantiocomplementary C–H Bond Hydroxylation Combining Photo-Catalysis and Whole-Cell Biocatalysis in a One-Pot Cascade Process
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Enantiocomplementary hydroxylation of alkyl aromatics through a one-pot photo-biocatalytic cascade reaction is described. The photoredox process is implemented in aqueous phase with O2 as oxidant and the subsequent (R)- or (S)-selective bioreduction is performed by whole cell system without the addition of the expensive cofactor (NADPH). This mild, operationally simple protocol transforms a wide variety of readily available aromatic compounds into valuable chiral alcohols with high yield (up to 90 %) and stereoselectivity (up to 99 %), thereby displaying important potentials in organic synthesis.
- Peng, Yongzhen,Li, Danyang,Fan, Jiajie,Xu, Weihua,Xu, Jian,Yu, Huilei,Lin, Xianfu,Wu, Qi
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supporting information
p. 821 - 825
(2020/02/20)
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- Iridium-Catalyzed Enantioselective Transfer Hydrogenation of Ketones Controlled by Alcohol Hydrogen-Bonding and sp3-C?H Noncovalent Interactions
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Iridium-catalyzed enantioselective transfer hydrogenation of ketones with formic acid was developed using a prolinol-phosphine chiral ligand. Cooperative action of the iridium atom and the ligand through alcohol-alkoxide interconversion is crucial to facilitate the transfer hydrogenation. Various ketones including alkyl aryl ketones, ketoesters, and an aryl heteroaryl ketone were competent substrates. An attractive feature of this catalysis is efficient discrimination between the alkyl and aryl substituents of the ketones, promoting hydrogenation with the identical sense of enantioselection regardless of steric demand of the alkyl substituent and thus resulting in a rare case of highly enantioselective transfer hydrogenation of tert-alkyl aryl ketones. Quantum chemical calculations revealed that the sp3-C?H/π interaction between an sp3-C?H bond of the prolinol-phosphine ligand and the aryl substituent of the ketone is crucial for the enantioselection in combination with O?H???O/sp3-C?H???O two-point hydrogen-bonding between the chiral ligand and carbonyl group. (Figure presented.).
- Murayama, Hiroaki,Heike, Yoshito,Higashida, Kosuke,Shimizu, Yohei,Yodsin, Nuttapon,Wongnongwa, Yutthana,Jungsuttiwong, Siriporn,Mori, Seiji,Sawamura, Masaya
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supporting information
p. 4655 - 4661
(2020/07/13)
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- P-chirogenic Trost ligands mediated asymmetric hydrogenation of simple ketones
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Herein, we report a highly active catalyst system consisting of (Rc,Rc,Rp,Rp)-P-chirogenic Trost ligand and [Ru(C6H6)Cl2]2 for asymmetric hydrogenation of simple ketones, affording the corresponding optically active alcohols in moderate enantioselectivity. A synergetic effect between P- and C-chirogenic centers of the P-chirogenic Trost ligands was observed in this asymmetric hydrogenation process.
- Du, Peng,Liu, Yan-Lan,Lu, Xiao-Bing
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supporting information
(2020/09/22)
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- Production of enantiomerically enriched chiral carbinols using whole-cell biocatalyst
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Biocatalytic asymmetric reduction of ketone is an efficient method for the production of chiral carbinols. The study indicates selective bioreduction of different ketones (1–8) to their respective (R)-alcohols (1a–8a) in low to high selectivity (0- >99%) with good yields (11–96%). In this work, whole-cell of Lactobacillus kefiri P2 catalysed enantioselective reduction of various prochiral ketones was investigated. (R)-4-Phenyl-2-butanol 2a, which is used as a precursor to antihypertensive agents and spasmolytics (anti-epileptic agents), was obtained using L kefiri P2 in 99% conversion and 91% enantiomeric excess (ee). Moreover, bioreduction of 2-methyl-1-phenylpropan-1-one substrate 8, containing a branched alkyl chain and difficult to asymmetric reduction with chemical catalysts as an enantioselective, to (R)-2-methyl-1-phenylpropan-1-ol (8a) in enantiomerically pure form was carried out in excellent yield (96%). The gram-scale production was carried out, and 9.70 g of (R)-2-methyl-1-phenylpropan-1-ol (8a) in enantiomerically pure form was obtained in 96% yield. Also especially, the yield and gram scale of (R)-2-methyl-1-phenylpropan-1-ol (8a) synthesised through catalytic asymmetric reduction using the biocatalyst was the highest report so far. The efficiency of L kefiri P2 for the conversion of the substrates and ee of products were markedly influenced by the steric factors of the substrates. This is a cheap, clean and eco-friendly process for production of chiral carbinols compared to chemical processes.
- ?ahin, Engin,Bayda?, Yasemin,Kalay, Erbay
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- Engineering a homochiral metal-organic framework based on an amino acid for enantioselective separation
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A chiral metal-organic framework possessing an open amphiphilic channel is constructed from a dicarboxylate ligand derived from an amino acid and is shown to be an efficient and recyclable chiral solid adsorbent, which is capable of separating racemic secondary alcohols, epoxides, and ibuprofen with very high enantioselectivity.
- Tang, Haitong,Yang, Keke,Wang, Kun-Yu,Meng, Qi,Wu, Fan,Fang, Yu,Wu, Xiang,Li, Yougui,Zhang, WenCheng,Luo, Yunfei,Zhu, Chengfeng,Zhou, Hong-Cai
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p. 9016 - 9019
(2020/08/17)
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- Redox-driven deracemization of secondary alcohols by sequential ether/O2-mediated oxidation and Ru-catalyzed asymmetric reduction
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The deracemization of benzylic alcohols has been achieved using a redox-driven one-pot two-step process. The racemic alcohols were oxidized by bis(methoxypropyl) ether and oxygen to give the ketone intermediates, followed by an asymmetric transfer hydrogenation with a chiral ruthenium catalyst. This compatible oxidation/reduction process gave the enantiomerically enriched alcohols with up to 95% ee values.
- Yang, Bing,Cui, Peng,Chen, Yongsheng,Liu, Qixing,Zhou, Haifeng
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- An Enantioconvergent Benzylic Hydroxylation Using a Chiral Aryl Iodide in a Dual Activation Mode
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The application of a triazole-substituted chiral iodoarene in a direct enantioselective hydroxylation of alkyl arenes is reported. This method allows the rapid synthesis of chiral benzyl alcohols in high yields and stereocontrol, despite its nontemplated nature. In a cascade activation consisting of an initial irradiation-induced radical C-H-bromination and a consecutive enantioconvergent hydroxylation, the iodoarene catalyst has a dual role. It initiates the radical bromination in its oxidized state through an in-situ-formed bromoiodane and in the second, Cu-catalyzed step, it acts as a chiral ligand. This work demonstrates the ability of a chiral aryl iodide catalyst acting both as an oxidant and as a chiral ligand in a highly enantioselective C-H-activating transformation. Furthermore, this concept presents an enantioconvergent hydroxylation with high selectivity using a synthetic catalyst.
- Abazid, Ayham H.,Clamor, Nils,Nachtsheim, Boris J.
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p. 8042 - 8048
(2020/09/21)
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- New chiral stationary phases for liquid chromatography based on small molecules: Development, enantioresolution evaluation and chiral recognition mechanisms
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Recently, we reported the development of new chiral stationary phases (CSPs) for liquid chromatography (LC) based on chiral derivatives of xanthones (CDXs). Based on the most promising CDX selectors, 12 new CSPs were successfully prepared starting from suitable functionalized small molecules including xanthone and benzophenone derivatives. The chiral selectors comprising one, two, three, or four chiral moieties were covalently bonded to a chromatographic support and further packed into LC stainless-steel columns (150?×?2.1?mm I.D.). The enantioselective performance of the new CSPs was evaluated by LC using different classes of chiral compounds. Specificity for enantioseparation of some CDXs was observed in the evaluation of the new CSPs. Besides, assessment of chiral recognition mechanisms was performed by computational studies using molecular docking approach, which are in accordance with the chromatographic parameters. X-Ray analysis was used to establish a chiral selector 3D structure.
- Phyo, Ye' Zaw,Teixeira, Joana,Tiritan, Maria Elizabeth,Cravo, Sara,Palmeira, Andreia,Gales, Luís,Silva, Artur M.S.,Pinto, Madalena M.M.,Kijjoa, Anake,Fernandes, Carla
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- Enantioselective Hydroxylation of Benzylic C(sp3)-H Bonds by an Artificial Iron Hydroxylase Based on the Biotin-Streptavidin Technology
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The selective hydroxylation of C-H bonds is of great interest to the synthetic community. Both homogeneous catalysts and enzymes offer complementary means to tackle this challenge. Herein, we show that biotinylated Fe(TAML)-complexes (TAML = Tetra Amido Macrocyclic Ligand) can be used as cofactors for incorporation into streptavidin to assemble artificial hydroxylases. Chemo-genetic optimization of both cofactor and streptavidin allowed optimizing the performance of the hydroxylase. Using H2O2 as oxidant, up to ~300 turnovers for the oxidation of benzylic C-H bonds were obtained. Upgrading the ee was achieved by kinetic resolution of the resulting benzylic alcohol to afford up to >98% ee for (R)-tetralol. X-ray analysis of artificial hydroxylases highlights critical details of the second coordination sphere around the Fe(TAML) cofactor.
- Barnet, Maxime,Peterson, Ryan L.,Rebelein, Johannes G.,Rumo, Corentin,Serrano-Plana, Joan,Ward, Thomas R.
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supporting information
p. 10617 - 10623
(2020/07/04)
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- Palladium Complexes Bearing Chiral bis(NHC) Chelating Ligands on a Spiro Scaffold: Synthesis, Characterization, and Their Application in the Oxidative Kinetic Resolution of Secondary Alcohols
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A series of chiral bis-N-heterocyclic carbene ligands H2[(S)-1a-d]X2 (X = Br, I) on a spiro scaffold and their palladium complexes (S)-2a-d and (S)-3a,b were prepared and applied in the enantioselective oxidative kinetic resolution of secondary alcohols. The corresponding alcohols can be obtained in high yields with moderate to excellent ee values.
- Zhang, Dao,Yu, Jueqin
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p. 605 - 613
(2020/02/13)
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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 transfer hydrogenation of ketones using Ru(0) nanoparticles modified by Chiral Thiones
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The catalytic asymmetric transfer hydrogenation (ATH) of acetophenone in isopropanol by Ru(0) nanoparticles (NPs) obtained by the in-situ reduction of Ru (II) half-sandwich complexes of chiral 2-oxazolidinethiones and 2-thiozolidinethiones was examined and compared with the catalytic activity of Ru(0) NPs formed in-situ by the reduction of [Ru(p-cymene)(Cl)2]2 in presence of optically active ligands such as (S)-4-isobutylthiazolidine-2-thione, (S)-4-Isopropyl-2(?2-pyridinyl)-2-oxazoline, (8S, 9R)-(?)-cinchonidine, (S)-leucinol, (S)-phenylalaninol, and (S)-leucine. Three of the best catalytic systems were then examined for ATH of thirteen aromatic ketones with different electronic and steric properties. A maximum of 24% ee was obtained using NPs generated from the Ru (II) half-sandwich complex with (S)-4-isobutylthiazolidine-2-thione in the TH of acetophenone. The NPs were characterized by TEM and DLS measurements. Kinetic studies and poisoning experiments confirmed that the reaction is catalyzed by the chiral NPs formed in-situ. Complete characterization of the complexes, including the X-ray crystallographic characterization of two complexes, was also carried out.
- Din Reshi, Noor U.,Senthurpandi, Dineshchakravarthy,Samuelson, Ashoka G.
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- Enantioselective Hydrogenation of Ketones using Different Metal Complexes with a Chiral PNP Pincer Ligand
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The synthesis of different metal pincer complexes coordinating to the chiral PNP ligand bis(2-((2R,5R)-2,5-dimethyl-phospholanoethyl))amine is described in detail. The characterized complexes with Mn, Fe, Re and Ru as metal centers showed good activities regarding the reduction of several prochiral ketones. Comparing these catalysts, the non-noble metal complexes produced best selectivities not only for aromatic substrates, but also for different kinds of aliphatic ones leading to enantioselectivities up to 99% ee. Theoretical investigations elucidated the mechanism and rationalized the selectivity. (Figure presented.).
- Garbe, Marcel,Wei, Zhihong,Tannert, Bianca,Spannenberg, Anke,Jiao, Haijun,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
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supporting information
p. 1913 - 1920
(2019/03/13)
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- Asymmetric Magnesium-Catalyzed Hydroboration by Metal-Ligand Cooperative Catalysis
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Asymmetric catalysis with readily available, cheap, and non-toxic alkaline earth metal catalysts represents a sustainable alternative to conventional synthesis methodologies. In this context, we describe the development of a first MgII-catalyzed enantioselective hydroboration providing the products with excellent yields and enantioselectivities. NMR spectroscopy studies and DFT calculations provide insights into the reaction mechanism and the origin of the enantioselectivity which can be explained by a metal-ligand cooperative catalysis pathway involving a non-innocent ligand.
- Falconnet, Alban,Magre, Marc,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 17567 - 17571
(2019/11/13)
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- Enhanced activity and modified substrate-favoritism of Burkholderia cepacia lipase by the treatment with a pyridinium alkyl-PEG sulfate ionic liquid
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Three types of pyridinium salts, i.e., 1-ethylpyridin-1-ium cetyl-PEG10 sulfate (PYET), 1-butylpyridin-1-ium cetyl-PEG10 sulfate (PYBU), and 1-(3-methoxypropyl)pyridin-1-ium cetyl-PEG10 sulfate (PYMP), have been prepared and evaluated for their activation property of Burkholderia cepacia lipase by comparison to the control IL-coated enzymes, 1-butyl-2,3-dimethylimidazolium cetyl-PEG10 sulfate-coated lipase PS (IL1-PS). Among the tested pyridinium salt-coated lipases, the PYET-coated lipase PS (PYET-PS) exhibited the best results; the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, 1-(pyridin-4-yl)ethanol, or 4-phenylbut-3-en-2-ol proceeded faster than those of the IL1-PS-catalyzed reaction while maintaining an excellent enantioselectivity (E > 200). This improved efficiency was found to be dependent on the increased Kcat value.
- Kadotani, Shiho,Nokami, Toshiki,Itoh, Toshiyuki
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p. 441 - 447
(2019/01/04)
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- Pickering Emulsion-Derived Liquid-Solid Hybrid Catalyst for Bridging Homogeneous and Heterogeneous Catalysis
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We describe a novel method to prepare a liquid-solid hybrid catalyst via interfacial growth of a porous silica crust around Pickering emulsion droplets, which allowed us to overcome the current limitations of both homogeneous and heterogeneous catalysts. The inner micron-scaled liquid (for example, ionic liquids) pool of the resultant catalyst can host free homogeneous molecular catalysts or enzymes to create a true homogeneous catalysis environment. The porous silica crust of the hybrid catalyst has excellent stability, which makes it amenable to packing directly in fixed-bed reactors for continuous flow catalysis. As a proof of concept, the enzymatic kinetic resolution of racemic alcohols, CrIII(salen) complex-catalyzed asymmetric ring opening of epoxides and Pd-catalyzed Tsuji-Trost allylic substitution reactions were used to verify the generality and versatility of our strategy for bridging homogeneous and heterogeneous catalysis. The hybrid catalyst-based continuous flow system exhibited a 1.6a16-fold enhancement in activity relative to homogeneous counterparts even over 1500 h, and the afforded enantioselectivities were completely equal to those obtained in the homogeneous counterpart systems. Interestingly, the catalytic efficiency can be tuned through rational engineering of the porous crust and the dimensions of the liquid pool, resulting in features of an innovatively designed catalyst. This contribution provides a new method to design efficient catalysts that can bridge the conceptual and technical gaps between homogeneous and heterogeneous catalysis.
- Zhang, Xiaoming,Hou, Yiting,Ettelaie, Rammile,Guan, Ruqun,Zhang, Ming,Zhang, Yabin,Yang, Hengquan
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supporting information
p. 5220 - 5230
(2019/03/11)
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- Cleavage of N-H Bond of Ammonia via Metal-Ligand Cooperation Enables Rational Design of a Conceptually New Noyori-Ikariya Catalyst
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The asymmetric transfer hydrogenation (ATH) of ketones/imines with Noyori-Ikariya catalyst represents an important reaction in both academia and fine chemical industry. The method allows for the preparation of chiral secondary alcohols/amines with very good to excellent optical purities. Remarkably, the same chiral Noyori-Ikariya complex is also a precatalyst for a wide range of other chemo- and stereoselective reductive and oxidative transformations. Among them are enantioselective sulfonamidation of acrylates (intramolecular aza-Michael reaction) and carboxylation of indoles with CO2. Development of these catalytic reactions has been inspired by the realized cleavage of the N-H bond of sulfonamides and indoles by the 16e- amido derivative of the 18e- precatalyst via metal-ligand cooperation (MLC). This paper summarizes our efforts to investigate N-H bond cleavage of gaseous ammonia in solution via MLC and reports the serendipitous discovery of a new class of chiral tridentate I3[N,N′,N″] Ru and Ir metallacycles, derivatives of the famous M-FsDPEN catalysts (M = Ru, Ir). The protonation of these metallacycles by strong acids containing weakly coordinating (chiral) anions generates ionic complexes, which were identified as conceptually novel Noyori-Ikariya precatalysts. For example, the ATH of aromatic ketones with some of these complexes proceeds with up to 99% ee.
- Dub, Pavel A.,Matsunami, Asuka,Kuwata, Shigeki,Kayaki, Yoshihito
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p. 2661 - 2677
(2019/02/14)
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- Plant-mediated enantioselective transformation of indan-1-one and indan-1-ol. Part 2
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The main purpose of this publication was to obtain the S-enantiomer of indan-1-ol with high enantiomeric excess and satisfactory yield. In our research, we used carrot callus cultures (Daucus carota L.), whereby the enzymatic system reduced indan-1-one an
- M?czka, Wanda,Wińska, Katarzyna,Grabarczyk, Ma?gorzata,Galek, Renata
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- Continuous Flow Asymmetric Transfer Hydrogenation with Long Catalyst Lifetime and Low Metal Leaching
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Homogenous iridium complexes with asymmetric ligands and different tether lengths have been solid-supported and prepared in multi-gram quantities. Packed in a fixed-bed, they have been used in continuous flow for up to 120 hours in the asymmetric transfer hydrogenation of APs in 2-propanol to make 1-phenethyl alcohols in > 95 % conversion and ee. The CsDPEN ligand and C5 tether showed higher performance than TsDPEN and the C14 tether, whilst the ketone feed concentration and reaction temperature were optimized to enable the catalyst to be used at 5 mol-% loading with a residence time of 39 minutes. The total amount iridium leaching of from the support during sustained operation was 58–147 ppm. The flow system gives higher catalyst turnover numbers than the related batch reactions, but the nature and concentration of the base were found to influence strongly the catalyst's performance, with the finding that triethylamine maintains high enantioselectivity but slowly deactivates the catalyst, whilst potassium tert-butoxide does the opposite. The utility of the system is shown in the high ee's and good conversions achieved for a range of aryl alcohols.
- Kawakami, Yuji,Borissova, Antonia,Chapman, Michael R.,Goltz, Gert,Koltsova, Eleonora,Mitrichev, Ivan,Blacker, A. John
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supporting information
p. 7499 - 7505
(2019/11/28)
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- Identification of an Esterase Isolated Using Metagenomic Technology which Displays an Unusual Substrate Scope and its Characterisation as an Enantioselective Biocatalyst
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Evaluation of an esterase annotated as 26D isolated from a marine metagenomic library is described. Esterase 26D was found to have a unique substrate scope, including synthetic transformations which could not be readily effected in a synthetically useful manner using commercially available enzymes. Esterase 26D was more selective towards substrates which had larger, more sterically demanding substituents (i. e. iso-propyl or tert-butyl groups) on the β-carbon, which is in contrast to previously tested commercially available enzymes which displayed a preference for substrates with sterically less demanding substituents (e.g. methyl group) at the β-carbon. (Figure presented.).
- Gavin, Declan P.,Murphy, Edel J.,Foley, Aoife M.,Castilla, Ignacio Abreu,Reen, F. Jerry,Woods, David F.,Collins, Stuart G.,O'Gara, Fergal,Maguire, Anita R.
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p. 2466 - 2474
(2019/03/11)
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- CHIRAL METAL COMPLEX COMPOUNDS
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The invention comprises novel chiral metal complex compounds of the formula (I) wherein M, PR2, R3 and R4 are outlined in the description, its stereoisomers, in the form as a neutral complex or a complex cation with a suitable counter ion. The chiral metal complex compounds can be used in asymmetric reactions, particularly in asymmetric reductions of ketones, imines or oximes.
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Page/Page column 18; 19; 20; 21; 24; 27
(2018/11/10)
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- Silylative Kinetic Resolution of Racemic 1-Indanol Derivatives Catalyzed by Chiral Guanidine
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Efficient kinetic resolution of racemic 1-indanol derivatives was achieved using triphenylchlorosilane by asymmetric silylation in the presence of chiral guanidine catalysts. The chiral guanidine catalyst (R,R)-N-(1-(β-naphthyl)ethyl)benzoguanidine was found to be highly efficient as only 0.5 mol % catalyst loading was sufficient to catalyze the reaction of various substrates with appropriate conversion and high s-values (up to 89). This catalyst system was successfully applied to the gram-scale silylative kinetic resolution of racemic 1-indanol with high selectivity.
- Yoshimatsu, Shuhei,Yamada, Akira,Nakata, Kenya
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p. 452 - 458
(2018/02/19)
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- The open d-shell enforces the active space in 3d metal catalysis: Highly enantioselective chromium(ii) pincer catalysed hydrosilylation of ketones
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Bis(oxazolinyldimethylmethyl)pyrrol (PdmBox) stereodirecting ligands provided the key to the chromium(ii)-catalysed highly enantioselective hydrosilylation of ketones. A rare square planar, chiral chromium(ii) alkyl complex was found to serve as a potent precatalyst for the reduction of a broad range of aryl alkyl and dialkyl ketone derivatives. The stereoelectronic preference of the open d4 shell of chromium(ii) firmly locks the molecular catalyst in a square planar geometry giving rise to two blocked quadrants of the coordination sphere. This earth-abundant base metal catalytic platform produces the corresponding chiral alcohols in excellent isolated yields with up to 98 %ee under mild reaction conditions (-40 °C to rt) and at low catalyst loadings (as low as 0.5 mol%).
- Schiwek, Christian H.,Vasilenko, Vladislav,Wadepohl, Hubert,Gade, Lutz H.
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supporting information
p. 9139 - 9142
(2018/08/24)
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- Engineering P450LaMO stereospecificity and product selectivity for selective C-H oxidation of tetralin-like alkylbenzenes
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The P450-mediated asymmetric hydroxylation of inert C-H bonds is a chemically challenging reaction. Self-sufficient P450LaMO from the CYP116B subfamily could catalyze the transformation of 1,2,3,4-tetrahydronaphthalene to (S)-tetralol, despite its poor enantioselectivity (er 66:34) and product selectivity (the ratio of alcohol and ketone, ak, 76:24). To improve the selectivity, phenylalanine scanning and further protein engineering were performed to reshape the active pocket of P450LaMO, resulting in a mutant (T121V/Y385F/M391L) with not only improved (S)-enantioselectivity (er 98:2) but also excellent product selectivity (ak 99:1), in contrast to another mutant L97F/T121F/E282V/T283Y with complementary (R)-enantioselectivity (er 23:77). Moreover, the enantiopure (S)-alcohols formed by the P450LaMO-catalyzed oxidation of a series of alkylbenzenes are potentially important building blocks in the pharmaceutical industry. This Phe-based enantioselectivity engineering used for reshaping the active pocket of P450s could provide a guide to the protein evolution of other CYP116B members.
- Li, Ren-Jie,Li, Aitao,Zhao, Jing,Chen, Qi,Li, Ning,Yu, Hui-Lei,Xu, Jian-He
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p. 4638 - 4644
(2018/09/29)
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- Design and Assembly of a Chiral Metallosalen-Based Octahedral Coordination Cage for Supramolecular Asymmetric Catalysis
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Supramolecular containers featuring both high catalytic activity and high enantioselectivity represent a design challenge of practical importance. Herein, it is demonstrated that a chiral octahedral coordination cage can be constructed by using twelve enantiopure Mn(salen)-derived dicarboxylic acids as linear linkers and six Zn4-p-tert-butylsulfonylcalix[4]arene clusters as tetravalent four-connected vertices. The porous cage features a large hydrophobic cavity (≈3944 ?3) decorated with catalytically active metallosalen species and is shown to be an efficient and recyclable asymmetric catalyst for the oxidative kinetic resolution of racemic secondary alcohols and the epoxidation of olefins with up to >99 % enantiomeric excess. The cage architecture not only prevents intermolecular deactivation and stabilizes the Mn(salen) catalysts but also encapsulates substrates and concentrates reactants in the cavity, resulting in enhanced reactivity and enantioselectivity relative to the free metallosalen catalyst.
- Tan, Chunxia,Jiao, Jingjing,Li, Zijian,Liu, Yan,Han, Xing,Cui, Yong
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supporting information
p. 2085 - 2090
(2018/02/06)
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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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p. 467 - 472
(2017/03/24)
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- Manganese(I)-Catalyzed Enantioselective Hydrogenation of Ketones Using a Defined Chiral PNP Pincer Ligand
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A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30–40 °C, 4 h, 30 bar H2). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry.
- Garbe, Marcel,Junge, Kathrin,Walker, Svenja,Wei, Zhihong,Jiao, Haijun,Spannenberg, Anke,Bachmann, Stephan,Scalone, Michelangelo,Beller, Matthias
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supporting information
p. 11237 - 11241
(2017/09/02)
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- Enantioselective bioreduction of benzo-fused cyclic ketones with engineered: Candida glabrata ketoreductase 1-a promising synthetic route to ladostigil (TV3326)
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Biocatalysis has been recently emerging as a promising alternative to traditional chemical synthesis because of its "green" characteristics and comparable selectivities, which accord with the concept of sustainable development and demand for asymmetric synthesis. In this study, whole-cell biocatalysts containing glucose dehydrogenase (GDH) and Candida glabrata ketoreductase 1 (CgKR1) variants were constructed. These biocatalysts were applied to the reduction of benzo-fused cyclic ketones and showed good to high activities and enantioselectivities. Particularly, CgKR1 variants displayed high activities (90.6%-98.4% conversions) and enantioselectivities (>99.9% ee) towards 5a, a key intermediate of ladostigil (TV3326). Based on these results, a chemoenzymatic synthesis of (S)-5b was developed by using biocatalytic asymmetric reduction as a key step, giving the product with a total yield of 34.0% and 99.9% ee.
- Ou-Yang, Jingping,Zhang, Wenhe,Qin, Fengyu,Zuo, Weiguo,Xu, Shaoyu,Wang, Yan,Qin, Bin,You, Song,Jia, Xian
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supporting information
p. 7374 - 7379
(2017/09/25)
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- Remarkably improved stability and enhanced activity of a: Burkholderia cepacia lipase by coating with a triazolium alkyl-PEG sulfate ionic liquid
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Three types of triazolium cetyl-PEG10 sulfate ionic liquid were synthesized and their activation of Burkholderia cepacia lipase was investigated; both the reaction rate and enantioselectivity depended on the cationic part of the coating ILs and 1-butyl-3-methyl-1,2,3-triazolium cetyl-PEG10 sulfate (Tz1)-coated lipase PS, which is especially suitable for the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, and 1-(pyridin-4-yl)ethanol, among 12 types of tested secondary alcohol. The most important result was obtained when these enzymes were stored in an IL ([N221MEM][Tf2N]) solvent: Tz1-PS showed an amazing stability and it exhibited an excellent activity after 2 years when the enzyme was stored in [N221MEM][Tf2N].
- Nishihara,Shiomi,Kadotani,Nokami,Itoh
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supporting information
p. 5250 - 5256
(2017/11/09)
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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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- The Oxidation of Hydrophobic Aromatic Substrates by Using a Variant of the P450 Monooxygenase CYP101B1
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The cytochrome P450 monooxygenase CYP101B1, from a Novosphingobium bacterium is able to bind and oxidise aromatic substrates but at a lower activity and efficiency than norisoprenoids and monoterpenoid esters. Histidine 85 of CYP101B1 aligns with tyrosine 96 of CYP101A1, which, in the latter enzyme forms the only hydrophilic interaction with its substrate, camphor. The histidine residue of CYP101B1 was mutated to phenylalanine with the aim of improving the activity of the enzyme for hydrophobic substrates. The H85F mutant lowered the binding affinity and activity of the enzyme for β-ionone and altered the oxidation selectivity. This variant also showed enhanced affinity and activity towards alkylbenzenes, styrenes and methylnaphthalenes. For example the rate of product formation for acenaphthene oxidation was improved sixfold to 245 nmol per nmol CYP per min. Certain disubstituted naphthalenes and substrates, such as phenylcyclohexane and biphenyls, were oxidised with lower activity by the H85F variant. Variants at H85 (A and G) designed to introduce additional space into the active site so as to accommodate these larger substrates did not improve the oxidation activity. As the H85F mutant of CYP101B1 improved the oxidation of hydrophobic substrates, this residue is likely to be in the substrate binding pocket or the access channel of the enzyme. The side chain of the histidine might interact with the carbonyl groups of the favoured norisoprenoid substrates of CYP101B1.
- Sarkar, Md. Raihan,Lee, Joel H. Z.,Bell, Stephen G.
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p. 2119 - 2128
(2017/10/12)
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- Asymmetric Autoamplification in the Oxidative Kinetic Resolution of Secondary Benzylic Alcohols Catalyzed by Manganese Complexes
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Herein, chiral Mn–aminopyridine complexes have been shown to catalyze the oxidation of alkylarenes to enantiomerically enriched 1-arylalkanols with hydrogen peroxide. The observed enantiomeric excess values result from the direct enantioselective benzylic C?H hydroxylation, accompanied by stereoconvergent oxidative kinetic resolution of the resulting alcohol. Testing several (S,S)-bipyrrolidine derived Mn complexes has revealed a novel catalyst (6) that exhibits the best kinetic resolution in the series (krel up to 8.8), along with sufficient reactivity and efficiency (>1000 catalytic turnovers). The mechanistic study of the Mn-mediated alcohol oxidation witnesses electrophilic active species (ρ=?1.2), with rate-limiting H abstraction (kH/kD=2.2), followed by oxygen rebound and dehydration of the resulting gem-diol to form the ketone. Intriguingly, while for the resolution of the relatively bulky 1,2-diphenylethanol, krel is virtually constant throughout the reaction, for less bulky alcohols, krel increases with increasing conversion, in line with the rising optical purity of the 1-arylalkanol. The latter participates in the oxidation as an auxiliary ligand, assisting the chiral recognition. This effect is related to the previously described asymmetric autocatalysis and asymmetric autoinduction, but is not identical with either of those, with the differences being discussed. To unambiguously identify this effect, the term asymmetric autoamplification (chiral autoamplification) is proposed.
- Talsi, Evgenii P.,Samsonenko, Denis G.,Bryliakov, Konstantin P.
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p. 2599 - 2607
(2017/07/12)
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- A convenient enantioselective CBS-reduction of arylketones in flow-microreactor systems
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A convenient, versatile, and green CBS-asymmetric reduction of aryl and heteroaryl ketones has been developed by using the microreactor technology. The study demonstrates that it is possible to handle borane solution safely within microreactors and that the reaction performs well using 2-MeTHF as a greener solvent.
- De Angelis, Sonia,De Renzo, Maddalena,Carlucci, Claudia,Degennaro, Leonardo,Luisi, Renzo
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supporting information
p. 4304 - 4311
(2016/05/24)
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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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- Transfer hydrogenation reactions catalyzed by chiral half-sandwich Ruthenium complexes derived from Proline
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Chiral ruthenium half-sandwich complexes were prepared using a chelating diamine made from proline with a phenyl, ethyl, or benzyl group, instead of hydrogen on one of the coordinating arms. Three of these complexes were obtained as single diastereoisomers and their configuration identified by X-ray crystallography. The complexes are recyclable catalysts for the reduction of ketones to chiral alcohols in water. A ruthenium hydride species is identified as the active species by NMR spectroscopy and isotopic labelling experiments. Maximum enantio-selectivity was attained when a phenyl group was directly attached to the primary amine on the diamine ligand derived from proline. [Figure not available: see fulltext.]
- Pandia Kumar, Arun Kumar,Samuelson, Ashoka G
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p. 1405 - 1415
(2016/09/19)
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- IRON(II) CATALYSTS CONTAINING TRIDENTATE PNP LIGANDS, THEIR SYNTHESIS, AND USE THEREOF
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The application describes catalytic materials for hydrogenation or asymmetric hydrogenation. In particular, the application describes iron(ll) complexes containing tridentate diphosphine PNP ligands useful for catalytic hydrogenation.
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Paragraph 0263
(2016/11/28)
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- HPLC enantioseparation on a homochiral MOF-silica composite as a novel chiral stationary phase
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The last frontier in the development of chiral stationary phases for chromatographic enantioseparation involves homochiral metal-organic frameworks (MOFs). Using enantiopure (R)-2,2′-dihydroxy-1,1′-binaphthalene-6,6′-dicarboxylic acid as a starting material, we prepared three homochiral MOFs that were further used as chiral stationary phases for high-performance liquid chromatography to separate the enantiomers of various kinds of racemic sulfoxides, sec-alcohols, β-lactams, benzoins, flavanones and epoxides. The experimental results showed excellent performances for enantioseparation, and highlighted that enantioseparation on homochiral MOF columns is practical.
- Tanaka, Koichi,Muraoka, Toshihide,Otubo, Yasuhiro,Takahashi, Hiroki,Ohnishi, Atsushi
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p. 21293 - 21301
(2016/03/08)
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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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- Stereospecific Synthesis of Alkenes by Eliminative Cross-Coupling of Enantioenriched sp3-Hybridized Carbenoids
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1-Aryl-1,2-dialkylethenes were generated by a sequence of electrophilic substitution, 1,2-metalate rearrangement, and β-elimination initiated by the addition of enantioenriched α-(carbamoyloxy)alkylboronates to enantioenriched lithiated carbamates. The carbenoid stereochemical pairing [i.e., “like”=(S)+(S) or “unlike”=(S)+(R)] and the elimination mechanism (syn or anti), not substituent effects, determined the configuration of the trisubstituted alkene target. For example, (Z)-2,5-diphenyl-2-pentene was produced in 70 % yield with E/Z=5:95 by a like combination of Li and B carbenoids and syn (thermal) elimination whereas the E isomer was obtained in the same yield with E/Z>98:2 by an otherwise identical process involving an unlike stereochemical pairing. The concept elaborated overcomes an intrinsic limitation of traditional strategies for direct connective alkene synthesis, which cannot realize meaningful stereochemical bias unless the alkene substituents are strongly differentiated.
- Wu, Zhenhua,Sun, Xun,Potter, Kristin,Cao, Yang,Zakharov, Lev N.,Blakemore, Paul R.
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supporting information
p. 12285 - 12289
(2016/10/13)
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- Chiral spiro-pyridylamidophosphine ligand compound, synthesis method therefor and application thereof
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The present invention relates to a chiral spiro-pyridylamidophosphine ligand compound, synthesis method therefor and application thereof. The chiral spiro-pyridylamidophosphine compound is a compound having a structure of Formula (I), a racemate or optical isomer thereof, or a catalytically acceptable salt thereof, and is mainly characterized by having a chiral spiro-dihydro-indene skeleton in its structure. The chiral spiro-pyridylamidophosphine compound may be synthesized with optical active 7-diaryl/alkylphosphino-7′-amino-1,1′-spiro-dihydro-indene or substituted 7-diaryl/alkylphosphino-7′-amino-1,1′-spiro-dihydro-indene having a spiro-skeleton as chiral starting material. The chiral spiro-pyridylamidophosphine compound may be used as a chiral ligand in asymmetric hydrogenation of a carbonyl compound catalyzed by iridium, in which the reaction activity is very high, the amount of the catalyst may be 0.0001 mol %, and the enantioselectivity of the reaction is up to 99.9% ee.
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Page/Page column 17; 18-20
(2015/03/03)
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