- Sequential Chiral Induction and Regulator-Assisted Chiral Memory of Pillar[5]arenes
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Chirality transfer is widely observed in life processes, and many artificial chiral transfer systems have been developed. In these systems, chiral information is transferred from chiral inducers to chiral acceptors by a direct chiral induction process and a direct chiral memorization process. We have developed ternary nondirect chiral transfer systems based on pillar[5]arenes, in which a third factor was introduced as a regulator. The planar chirality of an acceptor was induced and memorized by a chiral inducer with precise control by a regulator. In the chiral induction period, the feed sequence of the chiral inducer and regulator affected the chiral induction behavior of the chiral acceptor. The chiral memory ability of the acceptor was substantially improved by the combined action of the chiral inducer and regulator.
- Adachi, Keisuke,Egami, Kouichi,Fa, Shixin,Kato, Kenichi,Ogoshi, Tomoki
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Read Online
- Chemoselective and Tandem Reduction of Arenes Using a Metal–Organic Framework-Supported Single-Site Cobalt Catalyst
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The development of heterogeneous, chemoselective, and tandem catalytic systems using abundant metals is vital for the sustainable synthesis of fine and commodity chemicals. We report a robust and recyclable single-site cobalt-hydride catalyst based on a porous aluminum metal–organic framework (DUT-5 MOF) for chemoselective hydrogenation of arenes. The DUT-5 node-supported cobalt(II) hydride (DUT-5-CoH) is a versatile solid catalyst for chemoselective hydrogenation of a range of nonpolar and polar arenes, including heteroarenes such as pyridines, quinolines, isoquinolines, indoles, and furans to afford cycloalkanes and saturated heterocycles in excellent yields. DUT-5-CoH exhibited excellent functional group tolerance and could be reusable at least five times without decreased activity. The same MOF-Co catalyst was also efficient for tandem hydrogenation–hydrodeoxygenation of aryl carbonyl compounds, including biomass-derived platform molecules such as furfural and hydroxymethylfurfural to cycloalkanes. In the case of hydrogenation of cumene, our spectroscopic, kinetic, and density functional theory (DFT) studies suggest the insertion of a trisubstituted alkene intermediate into the Co–H bond occurring in the turnover limiting step. Our work highlights the potential of MOF-supported single-site base–metal catalysts for sustainable and environment-friendly industrial production of chemicals and biofuels.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Begum, Wahida,Chauhan, Manav,Newar, Rajashree,Rawat, Manhar Singh,Manna, Kuntal
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supporting information
p. 1031 - 1040
(2022/01/19)
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- Direct Synthesis of α-Amino Nitriles from Sulfonamides via Base-Mediated C-H Cyanation
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Herein, we disclose a transition-metal-free reaction system that enables α-cyanation of sulfonamides through C-H bond cleavage for the preparation of α-amino nitriles, including difficult-to-access all-alkyl α-tertiary scaffolds. More than 50 substrate examples prove a wide functional group tolerance. Additionally, its synthetic practicality is highlighted by gram-scalability and the late-stage modification of natural compounds. Mechanistic experiments suggest that this process involves in situ formation of an imine intermediate via base-promoted elimination of HF.
- Shi, Shasha,Yang, Xianyu,Tang, Man,Hu, Jiefeng,Loh, Teck-Peng
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supporting information
p. 4018 - 4022
(2021/05/26)
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- Asymmetric synthesis of primary amines catalyzed by thermotolerant fungal reductive aminases
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Chiral primary amines are important intermediates in the synthesis of pharmaceutical compounds. Fungal reductive aminases (RedAms) are NADPH-dependent dehydrogenases that catalyse reductive amination of a range of ketones with short-chain primary amines supplied in an equimolar ratio to give corresponding secondary amines. Herein we describe structural and biochemical characterisation as well as synthetic applications of two RedAms fromNeosartoryaspp. (NfRedAm andNfisRedAm) that display a distinctive activity amongst fungal RedAms, namely a superior ability to use ammonia as the amine partner. Using these enzymes, we demonstrate the synthesis of a broad range of primary amines, with conversions up to >97% and excellent enantiomeric excess. Temperature dependent studies showed that these homologues also possess greater thermal stability compared to other enzymes within this family. Their synthetic applicability is further demonstrated by the production of several primary and secondary amines with turnover numbers (TN) up to 14 000 as well as continous flow reactions, obtaining chiral amines such as (R)-2-aminohexane in space time yields up to 8.1 g L?1h?1. The remarkable features ofNfRedAmand NfisRedAm highlight their potential for wider synthetic application as well as expanding the biocatalytic toolbox available for chiral amine synthesis.
- Cosgrove, Sebastian C.,Grogan, Gideon,Mangas-Sanchez, Juan,Marshall, James R.,Palmer, Ryan B.,Ramsden, Jeremy I.,Sharma, Mahima,Thorpe, Thomas W.,Turner, Nicholas J.
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p. 5052 - 5057
(2020/06/09)
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- Ruthenium Catalyzed Direct Asymmetric Reductive Amination of Simple Aliphatic Ketones Using Ammonium Iodide and Hydrogen
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The direct conversion of ketones into chiral primary amines is a key transformation in chemistry. Here, we present a ruthenium catalyzed asymmetric reductive amination (ARA) of purely aliphatic ketones with good yields and moderate enantioselectivity: up to 99 percent yield and 74 percent ee. The strategy involves [Ru(PPh3)3H(CO)Cl] in combination with the ligand (S,S)-f-binaphane as the catalyst, NH4I as the amine source and H2 as the reductant. This is a straightforward and user-friendly process to access industrially relevant chiral aliphatic primary amines. Although the enantioselectivity with this approach is only moderate, to the extent of our knowledge, the maximum ee of 74 percent achieved with this system is the highest reported till now apart from enzyme catalysis for the direct transformation of ketones into chiral aliphatic primary amines.
- Ernst, Martin,Ghosh, Tamal,Hashmi, A. Stephen K.,Schaub, Thomas
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supporting information
(2020/07/14)
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- Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation
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Titania (TiO2) is widely used in the chemical industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying molecular mechanism is not understood due to the presence of multiple catalytic species on the TiO2 surface. This challenge can be addressed with metal-organic frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti8(μ2-O)8(μ2-OH)4 node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO2 support to enable CoII-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported CoII-hydride is strongly dependent on the reduction of the Ti-oxo cluster, definitively proving the pivotal role of TiIII in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understating the strong metal-support interaction of TiO2-supported heterogeneous catalysts.
- Ji, Pengfei,Song, Yang,Drake, Tasha,Veroneau, Samuel S.,Lin, Zekai,Pan, Xiandao,Lin, Wenbin
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p. 433 - 440
(2018/01/17)
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- O -Phthalaldehyde catalyzed hydrolysis of organophosphinic amides and other P(O)-NH containing compounds
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Over 50 years ago, Jencks and Gilchrist showed that formaldehyde catalyses the hydrolysis of phosphoramidate through electrophilic activation, induced by covalent attachment to its nitrogen atom. Given our interest in the use of aldehydes as catalysts, this work was revisited to identify a superior catalyst, o-phthalaldehyde, which facilitates hydrolyses of various organophosphorus compounds bearing P(O)-NH subunits under mild conditions. Interestingly, chemoselective hydrolysis of the P(O)-N bonds could be accomplished in the presence of P(O)-OR bonds.
- Li, Bin-Jie,Simard, Ryan D.,Beauchemin, André M.
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supporting information
p. 8667 - 8670
(2017/08/10)
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- Optical activity 1-cyclohexyl ethylamine preparation method
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The present invention discloses an optical activity 1-cyclohexyl ethylamine preparation method, which comprises that: in water and under the effect of HBr, N-acetylamino-1-cyclohexyl ethylamine represented by a formula 4 or 4' is subjected to a hydrolysis reaction to correspondingly prepare the optical activity 1-cyclohexyl ethylamine represented by a formula 5 or 5'. The preparation method of the present invention can further comprise that a compound represented by a formula I is subjected to an oximation reaction, a reduction acylation reaction and an asymmetric catalysis reaction to prepare the N-acetylamino-1-cyclohexyl ethylamine represented by the formula 4 or 4'. According to the present invention, the preparation method has characteristics of simple operation, low production cost, high product chemical purity, high product optical purity, high product yield, and green environmental protection. The formulas such as 4, 4', 5 and 5' are defined in the specification.
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- Imine Reductase-Catalyzed Intermolecular Reductive Amination of Aldehydes and Ketones
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Imine reductases (IREDs) have emerged as promising biocatalysts for the synthesis of chiral amines. In this study, the asymmetric imine reductase-catalyzed intermolecular reductive amination with NADPH as the hydrogen source was investigated. A highly chemo- and stereoselective imine reductase was applied for the reductive amination by using a panel of carbonyls with different amine nucleophiles. Primary and secondary amine products were generated in moderate to high yields with high enantiomeric excess values. The formation of the imine intermediate was studied between carbonyl substrates and methylamine in aqueous solution in the pH range of 4.0 to 9.0 by 1H NMR spectroscopy. We further measured the kinetics of the reductive amination of benzaldehyde with methylamine. This imine reductase-catalyzed approach constitutes a powerful and direct method for the synthesis of valuable amines under mild reaction conditions. IRED all about it: The intermolecular asymmetric reductive amination of carbonyls catalyzed by a stereoselective imine reductase produces chiral amines in high yields with high enantioselectivities. The reaction efficiency is attributed to its remarkable tolerance to high concentrations of amine nucleophiles, high pH values, high chemoselectivity towards imines, and high stereoselectivity of the biocatalyst.
- Scheller, Philipp N.,Lenz, Maike,Hammer, Stephan C.,Hauer, Bernhard,Nestl, Bettina M.
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p. 3239 - 3242
(2015/10/28)
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- CATALYST COMPOUNDS
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The present invention relates to an iridium-based catalyst compound for hydrogenating reducible moieties, especially imines and iminiums, the catalyst compounds being defined by the formulas: where ring B is either itself polycyclic, or ring B together with R is polycyclic. The catalysts of the invention are particularly effective in reductive amination procedures 10 which involve the in situ generation of the imine or iminium under reductive hydrogenative conditions.
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Paragraph 0314; 0322
(2015/03/28)
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- Primary amines by transfer hydrogenative reductive amination of ketones by using cyclometalated IrIII catalysts
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Cyclometalated iridium complexes are found to be versatile catalysts for the direct reductive amination (DRA) of carbonyls to give primary amines under transfer-hydrogenation conditions with ammonium formate as both the nitrogen and hydrogen source. These complexes are easy to synthesise and their ligands can be easily tuned. The activity and chemoselectivity of the catalyst towards primary amines is excellent, with a substrate to catalyst ratio (S/C) of 1000 being feasible. Both aromatic and aliphatic primary amines were obtained in high yields. Moreover, a first example of homogeneously catalysed transfer-hydrogenative DRA has been realised for β-keto ethers, leading to the corresponding β-amino ethers. In addition, non-natural α-amino acids could also be obtained in excellent yields with this method. Reduce the work! A broad range of ketones have been successfully aminated to afford primary amines under transfer-hydrogenation conditions by using ammonium formate as the amine source and 0.1 mol % of a cyclometalated IrIII catalyst (see scheme). Copyright
- Talwar, Dinesh,Salguero, Noemi Poyatos,Robertson, Craig M.,Xiao, Jianliang
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supporting information
p. 245 - 252
(2014/01/17)
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- Microwave-Enhanced Asymmetric Transfer Hydrogenation of N-(tert-Butylsulfinyl)imines
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Microwave irradiation has considerably enhanced the efficiency of the asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)imines in isopropyl alcohol catalyzed by a ruthenium complex bearing the achiral ligand 2-amino-2-methylpropan-1-ol. In addition to shortening reaction times for the transfer hydrogenation processes to only 30 min, the amounts of ruthenium catalyst and isopropyl alcohol can be considerably reduced in comparison with our previous procedure assisted by conventional heating, which diminishes the environmental impact of this new protocol. This methodology can be applied to aromatic, heteroaromatic and aliphatic N-(tert-butylsulfinyl)ketimines, leading, after desulfinylation, to the expected primary amines in excellent yields and with enantiomeric excesses of up to 96 %. Microwave irradiation promotes the asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)imines in 2-propanol catalysed by a ruthenium complex bearing an achiral β-amino alcohol as ligand. After desulfinylation, α-branched primary amines containing aromatic, heteroaromatic and aliphatic substituents are obtained in excellent yields and with enantiomeric excesses of up to 96 %.
- Pablo, Oscar,Guijarro, David,Yus, Miguel
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p. 7034 - 7038
(2016/02/19)
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- A highly fluorescent metallosalalen-based chiral cage for enantioselective recognition and sensing
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A highly fluorescent coordination cage [Zn8L4I 8] has been constructed by treating enantiopure pyridyl- functionalized metallosalalen units (L) with zinc(II) iodide and characterized by a variety of techniques including microanalysis, thermogravimetric analysis (TGA), circular dichroism (CD) spectroscopy, and single-crystal and powder X-ray diffraction. Strong intermolecular π-π, CH-π, and CH-I interactions direct packing of the cage molecules to generate a 3D polycage network interconnected by pentahedral cages formed by adjacent pentamers. The cage has an amphiphilic helical cavity decorated with chiral NH functionalities capable of interactions with guest species such as saccharides. The fluorescence of the cage was greatly enhanced by five enantiomeric saccharides in solution, with enantioselectivity factors of 2.480-4.943, and by five enantiomeric amines in the solid state, with enantioselective fluorescence enhancement ratios of 1.30-3.60. This remarkable chiral sensing of both saccharides and amines with impressive enantioselectivity may result from the steric confinement of the cavity as well as its conformational rigidity. It holds great promise for the development of novel chiral cage materials for sensing applications. Cage-based chiral sensor: A highly fluorescent coordination cage [Zn8L 4I8] can be prepared from enantiopure pyridyl- functionalized metallosalalen units (L). The cage has an amphiphilic helical cavity decorated with chiral NH functionalities and supramolecular interactions generate a 3D polycage network interconnected by pentahedral cages formed by adjacent pentamers (see graphic). The fluorescence of the cage is greatly enhanced either in solution or in the solid state in the presence of enantiomeric saccharides or amines, respectively, with significant enantioselectivity factors.
- Dong, Jinqiao,Zhou, Yanfang,Zhang, Fangwei,Cui, Yong
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supporting information
p. 6455 - 6461
(2014/06/09)
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- Nickel nanoparticles as racemization catalysts for primary amines
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By combining bases that are known to racemize benzylic amines with a nickel(II) salt, active nickel nanoparticles were obtained that can be used as catalysts in the racemization of both aliphatic and benzylic primary amines. The nanoparticles are stable in the ionic liquid tetrabutylammonium bromide and can complete most racemizations within a few hours with excellent selectivity. The problem of the incompatibility of the strongly reducing racemization catalyst and the enzymatic amine resolution catalyst was overcome by using a two-pot system with a biphasic racemization step. Consecutive contact of a nonane layer that contained the amine with the acylating enzyme and with the racemizing Ni nanoparticles in the ionic liquid allowed the 50 % amide yield limit of a kinetic resolution to be successfully surpassed. Copyright
- Geukens, Inge,Plessers, Eva,Seo, Jin Won,De Vos, Dirk E.
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p. 2623 - 2628
(2013/07/11)
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- CATALYST COMPOUNDS
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The present invention relates to an iridium-based catalyst compound for hydrogenating reducible moieties, especially imines and iminiums, the catalyst compounds being defined by the formulas: where ring B is either itself polycyclic, or ring B together with R is polycyclic. The catalysts of the invention are particularly effective in reductive amination procedures 10 which involve the in situ generation of the imine or iminium under reductive hydrogenative conditions.
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Paragraph 00163; 00171
(2013/11/05)
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- N-octanoyldimethylglycine trifluoroethyl ester, an acyl donor leading to highly enantioselective protease-catalysed kinetic resolution of amines
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The use of N-octanoyldimethylglycine trifluoroethyl ester as acyl donor in the kinetic resolution of aliphatic amines catalysed by proteases led to enantiomeric ratios >200 in most cases. The resolutions mediated by Protex 6L were shown to be much faster
- Queyroy, Severine,Vanthuyne, Nicolas,Gastaldi, Stephane,Bertrand, Michele P.,Gil, Gerard
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supporting information; experimental part
p. 1759 - 1764
(2012/08/08)
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- Enzymatic asymmetric synthesis of enantiomerically pure aliphatic, aromatic and arylaliphatic amines with (R)-selective amine transaminases
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Seven (R)-selective amine transaminases (R-ATAs) recently discovered by an in silico-based approach in sequence databases were produced recombinantly in Escherichia coli and subjected to partial purification by ammonium sulfate precipitation. A range of additives and various buffers were investigated to identify best conditions to ensure good storage stability and stable activity during biocatalysis. All enzymes show pH optima between pH 7.5-9. These R-ATAs were then applied in the asymmetric synthesis of twelve aliphatic, aromatic and arylaliphatic (R)-amines starting from the corresponding prochiral ketones using a lactate dehydrogenase/glucose dehydrogenase system to shift the equilibrium. For all ketones, at least one enzyme was found that allows complete conversion to the corresponding chiral amine having excellent optical purities >99% ee. Variations in substrate profiles are also discussed based on the phylogenetic relationships between the seven R-ATAs. Thus, we have identified a versatile toolbox of (R)-amine transaminases showing remarkable properties for application in biocatalysis. Copyright
- Schaetzle, Sebastian,Steffen-Munsberg, Fabian,Thontowi, Ahmad,Hoehne, Matthias,Robins, Karen,Bornscheuer, Uwe T.
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experimental part
p. 2439 - 2445
(2011/11/06)
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- Asymmetric synthesis of chiral primary amines by transfer hydrogenation of N -(tert -Butanesulfinyl)ketimines
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(Figure presented) The diastereoselective reduction of (R)-N-(tert- butanesulfinyl)ketimines by a ruthenium-catalyzed asymmetric transfer hydrogenation process in isopropyl alcohol, followed by desulfinylation of the nitrogen atom, is an excellent method to prepare highly enantiomerically enriched α-branched primary amines (up to >99% ee) in short reaction times (1-4 h). (1S,2R)-1-Amino-2-indanol has been shown to be a very efficient ligand to perform this transformation. Ketimines bearing either an aryl or a heteroaryl group and an alkyl group as substituents of the iminic carbon atom are very good substrates for this process. The reduction of a dialkyl ketimine could also be achieved, affording the expected amine with moderate optical purity (69% ee). Some amines which are precursors of very interesting biologically and pharmacologically active compounds have been prepared in excellent yields and enantiomeric excesses.
- Guijarro, David,Pablo, Oscar,Yus, Miguel
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supporting information; experimental part
p. 5265 - 5270
(2010/10/21)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 63
(2010/12/31)
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- Deracemisation of α-chiral primary amines by a one-pot, two-step cascade reaction catalysed by ω-transaminases
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Racemic a-chiral primary amines were deracemised to optically pure amines in up to >99 % conversion and >99 % ee within 48 h. The deracemisation was a result of a stereoinver- sion of one amine enantiomer; the formal stereoinversion was achieved by a one-pot, two-step procedure: in the first step, kinetic resolution of the chiral racemic amine was performed by employing a -transaminase to yield an intermediate ketone and the remaining optically pure amine; in the second step, the ketone intermediate was stereoselectively transformed into the amine by employing alanine as the amine donor and a -transaminase displaying opposite stereopref- erence than the -transaminase in the first step. In the second step, lactate dehydrogenase was used to remove the side product pyruvate to shift the unfavourable reaction equilibrium to the product side. Depending on the order of the en- antiocomplementary enzymes employed in the cascade, the (R), as well as the (S), enantiomer was accessible.
- Koszelewski, Dominik,Clay, Dorina,Rozzell, David,Kroutil, Wolfgang
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experimental part
p. 2289 - 2292
(2009/08/09)
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- N-Acyl glycinates as acyl donors in serine protease-catalyzed kinetic resolution of amines. Improvement of selectivity and reaction rate
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Enzymatic kinetic resolution of aliphatic and benzylic amines leading to (S)-amides was achieved by using alkaline protease as the catalyst and N-octanoyl glycine trifluoroethyl ester as the acyl donor; enantioselectivity ranged between 4 to 244, while reaction times were dramatically shortened and ranged between 15 min to 6 h. The 2008 Royal Society of Chemistry.
- Nechab, Malek,El Blidi, Lahssen,Vanthuyne, Nicolas,Gastaldi, Stephane,Bertrand, Michele P.,Gil, Gerard
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supporting information; scheme or table
p. 3917 - 3920
(2009/06/28)
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- 5-CYAN0-4- (PYRROLO [2, 3B] PYRIDINE-3-YL) -PYRIMIDINE DERIVATIVES USEFUL AS PROTEIN KINASE INHIBITORS
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The present invention relates to compounds useful as inhibitors of protein kinase. The invention also provides pharmaceutically acceptable compositions comprising said compounds and methods of using the compositions in the treatment of various disease, conditions, or disorders. The invention also provides processes for preparing compounds of the inventions.
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Page/Page column 66; 67
(2008/12/07)
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- Heterogeneous raney nickel and cobalt catalysts for racemization and dynamic kinetic resolution of amines
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Raney metals were studied as heterogeneous catalysts for racemization and dynamic kinetic resolution (DKR) of chiral amines, as an alternative to metals like palladium or ruthenium. Both Raney nickel and cobalt were able to selectively racemize various chiral amines with high selectivity. In the racemization of benzylic primary amines, the minor formation of side products, e.g., secondary amines, can be suppressed by varying the hydrogen pressure. In the racemization of aliphatic amines over Raney catalysts, the selectivity is very high, with the enantiomeric amine as the sole product. DKR of racemic aliphatic amines can be performed with immobilized Candida antarctica lipase B and Raney nickel in one pot; for 2-hexylamine, a yield of 95% of the acetylated amide was achieved, with 97% ee. Attention is devoted to the compatibility of the enzyme and the metal catalyst during the DKR. For benzylic primary amines, a two-pot process is proposed in which the liquid is alternatingly shuttled between two vessels containing the solid racemization catalyst and the biocatalyst. After 4 such cycles, the amide of (R)-1-phenylethylamine was obtained with 94% yield and more than 90% ee.
- Parvulescu, Andrei N.,Jacobs, Pierre A.,De Vos, Dirk E.
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scheme or table
p. 113 - 121
(2009/04/16)
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- Enantioselective oxidation of O-methyl-N-hydroxylamines using monoamine oxidase N as catalyst
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Enantioselective oxidation of racemic O-methyl-N- hydroxycyclohexylethylamine, using a variant of monoamine oxidase N (MAO-N) from Aspergillus niger, yields unreacted (R)-enantiomer (e.e. = 99%) together with the oxime exclusively in the (E)-configuration. The Royal Society of Chemistry.
- Eve, Tom S. C.,Wells, Andrew,Turner, Nicholas J.
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p. 1530 - 1531
(2008/02/04)
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- Catalytic Leuckart-Wallach-type reductive amination of ketones
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A Cp*Rh(III) complex catalyzes reductive amination of ketones using HCOONH4 at 50-70°C to give the corresponding primary amines in high yields. The reaction is clean and operationally simple and proceeds at a lower temperature and with higher chemoselectivity than the original Leuckart-Wallach reaction. The new method has been applied to the synthesis of α-amino acids directly from α-keto acids.
- Kitamura, Masato,Lee, Donghyun,Hayashi, Shinnosuke,Tanaka, Shinji,Yoshimura, Masahiro
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p. 8685 - 8687
(2007/10/03)
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- 2-aminobenzoxazole derivatives and combinatorial libraries thereof
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The present invention relates to novel 2-aminobenzoxazole derivative compounds of the following formula: wherein R1 to R4 and Z have the meanings provided herein. The invention further relates to combinatorial libraries containing two or more such compounds, as well as methods of preparing 2-aminobenzoxazole derivative compounds.
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- Highly efficient resolutions with isopropylidene glycerol 3-carboxy-2-naphthoate
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A number of chiral 1-arylethylamines and 1-alkylethylamines were resolved with the 3-carboxy-2-naphthoate of isopropylidene glycerol 2, previously reported to be an even more efficient resolving agent for 1-phenylethylamine than the corresponding hemiphthalate 1. The results obtained for the 1-arylethylamines confirm such a trend, revealing impressive resolution ability, in particular, for 1-(4-bromophenyl)-, 1-(4-nitrophenyl)- and 1-(2-naphthyl)ethylamine, whose enantiomers were almost quantitatively separated with (S)-2 by a single precipitation of the less soluble (S,S) diastereomeric salt. Additionally, the success of the resolutions of 1-alkylethylamines (1-phenyl-2-propylamine, 1-cyclohexylethylamine and 2-butylamine), which could not be resolved with 1, indicates that the novel carboxy ester 2 has a wider range of application than 1.
- Pallavicini, Marco,Bolchi, Cristiano,Fumagalli, Laura,Valoti, Ermanno,Villa, Luigi
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p. 2277 - 2282
(2007/10/03)
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- Stereoselective transformation of amines via chiral 2,4,6-triphenylpyridinium intermediates
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We herein report the preparation and the nucleophilic substitution of the chiral 2,4,6-triphenylpyridinium tetrafluoroborates 2a and 2b. The triphenylpyridinium intermediates were generated from homochiral amines (1a, 1b) and 2,4,6-triphenylpyrylium tetrafluoroborate and used as substrates for stereoselective nucleophilic substitution. The degree of inversion in the substitution reactions has been studied. The alcohol (3a, 3b) and azide (4a, 4b) products were obtained with >99 and 96-98% inversion of configuration, respectively.
- Said, Sadri A.,Fiksdahl, Anne
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p. 1947 - 1951
(2007/10/03)
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- N,N-1,2-benzenedisulfonylimide, a new cyclic leaving group for the stereoselective nucleophilic substitution of amines
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We hereby report the preparation and nucleophilic substitutions of the N,N-1,2-benzenedisulfonylimide derivatives la and 2a of the chiral amines 1 and 2. The nucleophilic attack of KNO2 afforded the respective alcohols 3 and 4 with 84-90% inversion of configuration. Nucleophilic attack by the azide ion afforded the azide products 5 and 6 which were reduced to the corresponding inverted mines 1 and 2 (94-98.5% inversion). The improved leaving group ability of the N,N-1,2-benzenedisulfonylimides compared with previously reported N,N-disulfonylimides is discussed. Chiral GLC analysis of all products is summarized and the alternative chiral analysis of product 3 by 13C NMR using heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin as a chiral solvating agent (CSA) is discussed.
- Sorbye, Karsten,Tautermann, Christoffer,Carlsen, Per,Fiksdahl, Anne
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p. 681 - 689
(2007/10/03)
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- Catalytic asymmetric reductive amination of ketones via highly enantioselective hydrogenation of the C=N double bond
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We describe a convenient, chemoselective asymmetric reductive amination procedure for the conversion of ketones to chiral hydrazines and amines. The key step in the three-step process is enantioselective DuPHOS-Rh-catalyzed hydrogenation of the C=N double bond of N-acylhydrazones. Detailed optimization studies revealed the effect of solvent, temperature, and the N- acyl group on the enantioselectivity and catalytic efficiency of the reaction. The reduction products, N-acylhydrazines, were converted to hydrazines or amines through hydrolysis or treatment with samarium(II) iodide, respectively.
- Burk, Mark J.,Martinez, Jose P.,Feaster, John E.,Cosford, Nick
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p. 4399 - 4428
(2007/10/02)
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- Asymmetric Syntheses. Part 11. Reduction of Ketones and Related Ketone Oximes with Lithium Aluminium Hydride-3-O-cyclohexylmethyl-1,2-O-cyclohexylidene-α-D-glucofuranose Complex to give Optically Active Alcohols and Amines
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The asymmetric reduction of ketones and structurally related isoelectronic ketone oximes with lithium aluminium hydride-3-O-cyclohexylmethyl-1,2-O-cyclohexylidene-α-D-glucofuranose complex yields optically active alcohols of up to 42percent optical purity and optically active amines of up to 52percent optical purity, respectively.The resulting alcohols as well as amines all have the S-configuration.When the asymmetric reduction is carried out with the ethanol-modified glucofuranose complex, the resulting alcohols and amines have the R-configuration.
- Landor, Stephen R.,Chan, Yuet M.,Sonola, Olutunji O.,Tatchell, Austin R.
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p. 493 - 496
(2007/10/02)
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- BASIC STUDY OF THE AMINO ACID RESIDUE IN PROTEIN. THE ROLE OF HYDROCARBON GROUPS IN ENANTIOMER-DIFFERENTIATING ACYLATION.
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The enantiomer-differentiation acylation (kinetic resolution) of 1-phenylalkylamines and their derivatives was carried out with (S)-2-phenylbutyric anhydride and its derivatives in aqueous and nonaqueous media. On the basis of the distributions of the two diastereomeric products, the molecular interactions between hydrocarbon residues responsible for the structural recognition of the reacting molecules were studied. In nonpolar media, the (R,S)-isomer was predominantly formed over the (S,S)-isomer. Moreover, the differentiation was mainly controlled by the size of the alkyl substituents of the substrates.
- Hiraki,Tai
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p. 1570 - 1575
(2007/10/02)
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