- Engineering the large pocket of an (S)-selective transaminase for asymmetric synthesis of (S)-1-amino-1-phenylpropane
-
Amine transaminases offer an environmentally benign chiral amine asymmetric synthesis route. However, their catalytic efficiency towards bulky chiral amine asymmetric synthesis is limited by the natural geometric structure of the small pocket, representing a great challenge for industrial applications. Here, we rationally engineered the large binding pocket of an (S)-selective ?-transaminase BPTA fromParaburkholderia phymatumto relieve the inherent restriction caused by the small pocket and efficiently transform the prochiral aryl alkyl ketone 1-propiophenone with a small substituent larger than the methyl group. Based on combined molecular docking and dynamic simulation analyses, we identified a non-classical substrate conformation, located in the active site with steric hindrance and undesired interactions, to be responsible for the low catalytic efficiency. By relieving the steric barrier with W82A, we improved the specific activity by 14-times compared to WT. A p-p stacking interaction was then introduced by M78F and I284F to strengthen the binding affinity with a large binding pocket to balance the undesired interactions generated by F44. T440Q further enhanced the substrate affinity by providing a more hydrophobic and flexible environment close to the active site entry. Finally, we constructed a quadruple variant M78F/W82A/I284F/T440Q to generate the most productive substrate conformation. The 1-propiophenone catalytic efficiency of the mutant was enhanced by more than 470-times in terms ofkcat/KM, and the conversion increased from 1.3 to 94.4% compared with that of WT, without any stereoselectivity loss (ee > 99.9%). Meanwhile, the obtained mutant also showed significant activity improvements towards various aryl alkyl ketones with a small substituent larger than the methyl group ranging between 104- and 230-fold, demonstrating great potential for the efficient synthesis of enantiopure aryl alkyl amines with steric hindrance in the small binding pocket.
- Liu, He,Wang, Hualei,Wei, Dongzhi,Xie, Youyu,Xu, Feng,Xu, Xiangyang,Yang, Lin
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p. 2461 - 2470
(2021/04/22)
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- New chiral stationary phases for liquid chromatography based on small molecules: Development, enantioresolution evaluation and chiral recognition mechanisms
-
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
-
-
- In Vitro and in Vivo One-Pot Deracemization of Chiral Amines by Reaction Pathway Control of Enantiocomplementary ω-Transaminases
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Biocatalytic cascade conversion of racemic amines into optically pure ones using enantiocomplementary ω-transaminases (ω-TAs) has been developed by thermodynamic and kinetic control of reaction pathways where 12 competing reactions occur with pyruvate and isopropylamine used as cosubstrates. Thermodynamic control was achieved under reduced pressure for selective removal of a coproduct (i.e., acetone), leading to elimination of six undesirable reactions. Engineered orthogonality in substrate specificities of ω-TAs was exploited for kinetic control, enabling suppression of four additional reactions. Taken together, the net reaction pathway could be directed to two desired reactions (i.e., oxidative deamination of R-amine and reductive amination of the resulting ketone into antipode S-amine). This strategy afforded one-pot deracemization of various chiral amines with >99% eeS and 85-99% reaction yields of the resulting S-amine products. The in vitro cascade reaction could be successfully implemented in a live microbe using glucose or l-threonine as a cheap amino acceptor precursor, demonstrating a synthetic metabolic pathway enabling deracemization of chiral amines which has never been observed in living organisms.
- Han, Sang-Woo,Jang, Youngho,Shin, Jong-Shik
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p. 6945 - 6954
(2019/08/26)
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- Preparation of chiral primary amine through asymmetric reductive amination of simple ketone under catalytic action of ruthenium-diphosphine catalyst
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The invention relates to a method for preparing chiral primary amine. The method comprises the steps: performing a hydrogenation reductive amination reaction on simple ketone and an ammonium salt RCOONH4 under the action of a ruthenium-chiral diphosphine catalyst, then adding an acid, performing heating for hydrolysis, and adopting a one-pot method to prepare the chiral primary amine. The method has the advantages of good universality of the substrate, high reaction efficiency and the like.
- -
-
Paragraph 0077-0079
(2019/07/04)
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- Evaluation of the Edman degradation product of vancomycin bonded to core-shell particles as a new HPLC chiral stationary phase
-
A modified macrocyclic glycopeptide-based chiral stationary phase (CSP), prepared via Edman degradation of vancomycin, was evaluated as a chiral selector for the first time. Its applicability was compared with other macrocyclic glycopeptide-based CSPs: TeicoShell and VancoShell. In addition, another modified macrocyclic glycopeptide-based CSP, NicoShell, was further examined. Initial evaluation was focused on the complementary behavior with these glycopeptides. A screening procedure was used based on previous work for the enantiomeric separation of 50 chiral compounds including amino acids, pesticides, stimulants, and a variety of pharmaceuticals. Fast and efficient chiral separations resulted by using superficially porous (core-shell) particle supports. Overall, the vancomycin Edman degradation product (EDP) resembled TeicoShell with high enantioselectivity for acidic compounds in the polar ionic mode. The simultaneous enantiomeric separation of 5 racemic profens using liquid chromatography-mass spectrometry with EDP was performed in approximately 3?minutes. Other highlights include simultaneous liquid chromatography separations of rac-amphetamine and rac-methamphetamine with VancoShell, rac-pseudoephedrine and rac-ephedrine with NicoShell, and rac-dichlorprop and rac-haloxyfop with TeicoShell.
- Hellinghausen, Garrett,Lopez, Diego A.,Lee, Jauh T.,Wang, Yadi,Weatherly, Choyce A.,Portillo, Abiud E.,Berthod, Alain,Armstrong, Daniel W.
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p. 1067 - 1078
(2018/08/01)
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- Asymmetric Synthesis of Chiral Primary Amines by Ruthenium-Catalyzed Direct Reductive Amination of Alkyl Aryl Ketones with Ammonium Salts and Molecular H2
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A ruthenium/C3-TunePhos catalytic system has been identified for highly efficient direct reductive amination of simple ketones. The strategy makes use of ammonium acetate as the amine source and H2 as the reductant and is a user-friendly and operatively simple access to industrially relevant primary amines. Excellent enantiocontrol (>90% ee for most cases) was achieved with a wide range of alkyl aryl ketones. The practicability of this methodology has been highlighted by scalable synthesis of key intermediates of three drug molecules. Moreover, an improved synthetic route to the optimal diphosphine ligand C3-TunePhos is also presented.
- Tan, Xuefeng,Gao, Shuang,Zeng, Weijun,Xin, Shan,Yin, Qin,Zhang, Xumu
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supporting information
p. 2024 - 2027
(2018/02/19)
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- Enantioselective synthesis of amines via reductive amination with a dehydrogenase mutant from Exigobacterium sibiricum: Substrate scope, co-solvent tolerance and biocatalyst immobilization
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In recent years, the reductive amination of ketones in the presence of amine dehydrogenases emerged as an attractive synthetic strategy for the enantioselective preparation of amines starting from ketones, an ammonia source, a reducing reagent and a cofactor, which is recycled in situ by means of a second enzyme. Current challenges in this field consists of providing a broad synthetic platform as well as process development including enzyme immobilization. In this contribution these issues are addressed. Utilizing the amine dehydrogenase EsLeuDH-DM as a mutant of the leucine dehydrogenase from Exigobacterium sibiricum, a range of aryl-substituted ketones were tested as substrates revealing a broad substrate tolerance. Kinetics as well as inhibition effects were also studied and the suitability of this method for synthetic purpose was demonstrated with acetophenone as a model substrate. Even at an elevated substrate concentration of 50 mM, excellent conversion was achieved. In addition, the impact of water-miscible co-solvents was examined, and good activities were found when using DMSO of up to 30% (v/v). Furthermore, a successful immobilization of the EsLeuDH-DM was demonstrated utilizing a hydrophobic support and a support for covalent binding, respectively, as a carrier.
- L?we, Jana,Ingram, Aaron A.,Gr?ger, Harald
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p. 1387 - 1392
(2018/03/21)
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- Application of “Smart” Amine Donors for Rapid Screening and Scale-Up of Transaminase-Mediated Biotransformations
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The “smart” amine donors o-xylylenediamine and cadaverine were employed for the rapid screening of a large ketone library and subsequent preparative-scale synthesis of selected compounds using a commercially available amine transaminase, ATA256. The methodology enables both screening and preparative-scale biotransformations to be performed with a single enzyme and simplifies the generation of sp3-rich small-molecule libraries.
- Gomm, Andrew,Grigoriou, Stylianos,Peel, Christopher,Ryan, James,Mujtaba, Nafees,Clarke, Thomas,Kulcinskaja, Evelina,O'Reilly, Elaine
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supporting information
p. 5282 - 5284
(2018/09/14)
-
- Mapping the substrate scope of monoamine oxidase (MAO-N) as a synthetic tool for the enantioselective synthesis of chiral amines
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A library of 132 racemic chiral amines (α-substituted methylbenzylamines, benzhydrylamines, 1,2,3,4-tetrahydronaphthylamines (THNs), indanylamines, allylic and homoallylic amines, propargyl amines) was screened against the most versatile monoamine oxidase (MAO-N) variants D5, D9 and D11. MAO-N D9 exhibited the highest activity for most substrates and was applied to the deracemisation of a comprehensive set of selected primary amines. In all cases, excellent enantioselectivity was achieved (e.e. >99%) with moderate to good yields (55–80%). Conditions for the deracemisation of primary amines using a MAO-N/borane system were further optimised using THN as a template addressing substrate load, nature of the enzyme preparation, buffer systems, borane sources, and organic co-solvents.
- Herter, Susanne,Medina, Florian,Wagschal, Simon,Benha?m, Cyril,Leipold, Friedemann,Turner, Nicholas J.
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p. 1338 - 1346
(2017/10/06)
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- A Single Lipase-Catalysed One-Pot Protocol Combining Aminolysis Resolution and Aza-Michael Addition: An Easy and Efficient Way to Synthesise β-Amino Acid Esters
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A novel one-pot protocol combining aza-Michael addition and aminolysis resolution was developed to obtain chiral β-amino acid esters with lipase B from Candida antarctica (CAL-B) as the only catalyst. This method is conducted under mild reaction conditions and is very easy to handle. After a series of detailed optimization studies, ten racemic aromatic or aliphatic amines were subjected to this one-pot procedure, and twelve chiral β-amino acid esters and ten chiral amides were successfully synthesised with excellent ee values in theoretical yields. Scaled-up procedures also worked without apparent reduction in reaction rate or enantioselectivity, which makes this method suitable for large-scale production of chiral β-amino acid esters. A one-pot protocol for simultaneous synthesis of chiral β-amino acid esters and amides was developed by combining single lipase B from Candida antarctica (CAL-B) catalysed aza-Michael addition and aminolysis resolution. This method requires mild reaction conditions and is very easy to handle. Chiral β-amino acid esters and chiral amides were obtained with excellent ee values and in theoretical yields.
- Xu, Fan,Wu, Qiongsi,Chen, Xiaoyang,Lin, Xianfu,Wu, Qi
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p. 5393 - 5401
(2015/08/24)
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- Mechanism-Guided Engineering of ω-Transaminase to Accelerate Reductive Amination of Ketones
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Asymmetric reductive amination of ketones using ω-transaminases (ω-TAs) offers a promising alternative to the chemocatalytic synthesis of chiral amines. One fundamental challenge to the biocatalytic strategy is the very low enzyme activities for most ketones compared with native substrates (i.e., cat/KM for acetophenone). The W58L mutant afforded an efficient synthesis of enantiopure amines (i.e., >99% ee) using isopropylamine as an amino donor.
- Han, Sang-Woo,Park, Eul-Soo,Dong, Joo-Young,Shin, Jong-Shik
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p. 1732 - 1740
(2015/06/02)
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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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- Modification of supported Pd catalysts by alkalic salts in the selective racemization and dynamic kinetic resolution of primary amines
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Supported Pd nanoparticles (PdNPs) were modified with various alkalic salts by incipient wetness impregnation method. The effect of the salts on the catalytic activity and selectivity behavior of Pd catalysts for the racemization of (S)-1-phenylethylamine was investigated. The presence of alkalic salts can greatly enhance the selectivity of Pd catalysts, without significantly decreasing the catalytic activity. This modification method is suitable for PdNPs supported on various supports, such as micro/mesoporous silica and activated carbon. Combined with the immobilized lipases (Novozyme 435), this catalyst system can efficiently catalyze the dynamic kinetic resolution (DKR) of 1-phenylethylamine with yield and enantioselectivity up to 97% and 99%, respectively. The Royal Society of Chemistry.
- Jin, Qianru,Jia, Guoqing,Zhang, Yanmei,Li, Can
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p. 464 - 471
(2014/02/14)
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- Asymmetric synthesis of nonracemic primary amines via spiroborate-catalyzed reduction of pure (E)- and (Z)-O-benzyloximes: Applications toward the synthesis of calcimimetic agents
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Highly enantiopure (1-aryl)- and (1-naphthyl)-1-ethylamines were synthesized by the borane-mediated reduction of single-isomeric (E)- and (Z)-O-benzyloxime ethers using the stable spiroborate ester derived from (S)-diphenyl valinol and ethylene glycol as the chiral catalyst. Primary (R)-arylethylamines were prepared by the reduction of pure (Z)-ethanone oxime ethers in up to 99% ee using 15% of catalyst. Two convenient and facile approaches to the synthesis of new and known calcimimetic analogues employing enantiopure (1-naphthalen-1-yl)ethylamine as chiral precursor are described.
- Ou, Wenhua,Espinosa, Sandraliz,Meléndez, Héctor J.,Farré, Silvia M.,Alvarez, Jaime L.,Torres, Valerie,Martínez, Ileanne,Santiago, Kiara M.,Ortiz-Marciales, Margarita
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p. 5314 - 5327
(2013/07/25)
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- Asymmetric synthesis of novel (1h-benzo[d]imidazol -2-ylthio)- and (di-n-butylamino-2-ylthio)acetamides
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Asymmetric synthesis of novel (1H-benzo[d]imidazol-2-ylthio)- and (di-n-butylamino)acetamides is described. The o-nitrobenzyl oxime ethers were reduced with borane in the presence of oxazaborolidenes derived from norephedrine or diphenylvalinol and diphenylphosphinic amide was reduced with modified sodium tetrahydroborate catalyzed with β-ketoiminato cobalt(II) complex to the corresponding amines with high yields and moderate enantiomeric excess. Reaction of amines with 2-chloroacetyl chloride and next with thiobenzimidazole or n-dibutylamine gave corresponding products with high yields.
- Laczkowski, Krzysztof Z.
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p. 237 - 244
(2013/06/04)
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- An efficient single-enzymatic cascade for asymmetric synthesis of chiral amines catalyzed by ω-transaminase
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An efficient single-enzymatic cascade approach for the asymmetric synthesis of chiral amines has been developed, which applies the amino donor 3-aminocyclohexa-1,5-dienecarboxylic acid spontaneously tautomerizing to reach reaction completion with excellen
- Wang, Bo,Land, Henrik,Berglund, Per
-
supporting information
p. 161 - 163
(2013/02/23)
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- Enantioselective reduction of ketoxime ethers with borane-oxazaborolidines and synthesis of the key intermediate leading to (S)-rivastigmine
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The reduction of representative alkyl aryl (E)-ketoxime O-benzyl ethers with borane catalyzed by terpene oxazaborolidines, derived from (1R)-nopinone and (1R)-camphor, gave the corresponding amines with 82-99% ee. Oxazaborolidines derived from (1S)-2-carene and (1S)-3-carene were less selective. (S)-1-(3-Methoxyphenyl)ethanamine (94% ee) the key intermediate in the synthesis of (S)-rivastigmine, was obtained by the reduction of (E)-1-(3-methoxyphenyl) ethanone O-benzyl oxime with borane/oxazaborolidine generated from (S)-valinol.
- Pakulski, Marcin M.,Mahato, Sanjit K.,Bosiak, Mariusz J.,Krzeminski, Marek P.,Zaidlewicz, Marek
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p. 716 - 721
(2012/09/21)
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- N-octanoyldimethylglycine trifluoroethyl ester, an acyl donor leading to highly enantioselective protease-catalysed kinetic resolution of amines
-
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)
-
- Achiral β-amino alcohols as efficient ligands for the ruthenium-catalysed asymmetric transfer hydrogenation of sulfinylimines
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Some achiral β-amino alcohols have been shown as efficient ligands for the ruthenium-catalysed asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)imines in isopropanol. The ruthenium complex prepared from [RuCl2(p-cymene)]2 (2.5 mol %) and 2-amino-2-methyl-1- propanol (5 mol %) leads to α-branched chiral primary amines with very high optical purities (up to 98% ee) by the diastereoselective reduction of the imines followed by removal of the sulfinyl group under mild acidic conditions. Short reaction times (2-3 h) were needed to complete the reduction reactions when they were performed at 50 °C.
- Guijarro, David,Pablo, óscar,Yus, Miguel
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experimental part
p. 789 - 791
(2011/03/20)
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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; 62
(2010/12/31)
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- Chemoenzymatic asymmetric total synthesis of (S)-Rivastigmine using ω-transaminases
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A straightforward, high-yielding, chemoenzymatic total synthesis of enantiopure (S)-Rivastigmine was developed using various ω-transaminases for the asymmetric amination of appropriate acetophenone precursors. Optimisation of the biotransformation allowed scale-up and the total synthesis of (S)-Rivastigmine. The Royal Society of Chemistry 2010.
- Fuchs, Michael,Koszelewski, Dominik,Tauber, Katharina,Kroutil, Wolfgang,Faber, Kurt
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supporting information; experimental part
p. 5500 - 5502
(2010/10/19)
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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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- Ruthenium-catalysed asymmetric transfer hydrogenation of N-(tert-butanesulfinyl)imines
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The ruthenium complex prepared from [RuCl2(p-cymene)]2 and (1S,2R)-1-amino-2-indanol is a very efficient catalyst for the asymmetric transfer hydrogenation of (R)-N-(tert-butanesulfinyl)ketimines in isopropanol. By carefully removing
- Guijarro, David,Pablo, óscar,Yus, Miguel
-
experimental part
p. 5386 - 5388
(2009/12/06)
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- Asymmetric synthesis of N-substituted N-hydroxyureas
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Asymmetric synthesis of (S)-N-(1-arylethyl)-N-hydroxyureas, (S)-N-(6-methoxy)- and (S)-N-(6-benzyloxy-2,3-dihydrobenzofuran-3-yl)-N-hydroxyurea- lipoxygenase inhibitor, is described. Three approaches to the formation of the N-hydroxyurea moiety at the stereogenic center have been used. The first one, via the reaction of (R)-6-benzyloxy-2,3-dihydrobenzofuran-3-ol with N,O-bis(phenoxycarbonyl)hydroxylamine under Mitsunobu conditions, leads to a partially racemized product. Alternatively, the enantioselective reduction of oximes O-benzyl ethers of acetophenone, 4-methoxy- and 4-benzyloxyacetophenone, 6-methoxy- and 6-benzyloxy-2,3-dihydrobenzofuran-3-one with borane/oxazaborolidines can be controlled to produce either the corresponding hydroxylamine O-benzyl ethers or primary amines which have been transformed into N-substituted N-hydroxyureas in 57% to 99% ee.
- Laczkowski, Krzysztof Z.,Pakulski, Marcin M.,Krzeminski, Marek P.,Jaisankar, Parasuraman,Zaidlewicz, Marek
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p. 788 - 795
(2008/09/20)
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- Enantioselective hydrosilylation of ketimines with trichlorosilane promoted by chiral N-picolinoylaminoalcohols
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Enantioselective hydrosilylation of N-aryl and N-benzyl ketimines with trichlorosilane catalyzed by readily accessible chiral N-picolinoylaminoalcohols proceeded smoothly furnishing chiral secondary amines in good yields (up to 93%) and moderate to excellent enantioselectivities (up to 95% ee).
- Zheng, Hongjie,Deng, Jingen,Lin, Wenqing,Zhang, Xiaomei
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p. 7934 - 7937
(2008/03/14)
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- Palladium catalysts on alkaline-earth supports for racemization and dynamic kinetic resolution of benzylic amines
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Palladium catalysts on alka-line-earth supports were studied as new heterogeneous catalysts for racemization of chiral benzylic amines such as 1-phenylethylamine. Particularly 5% Pd/BaSO4 and 5% Pd/CaCO 3 were able to selectively racemize amines, with minimal formation of secondary amines or hydrogenolysis to ethylbenzene. In contrast, these side reactions were pronounced on Pd/C. A reaction mechanism is proposed that is consistent with the reaction kinetics. The catalyst activity was found to depend on the number of available surface Pd atoms, determined by titration with CO. The selectivity crucially depends on the rate of condensation of the amine and the primary imine. which is highest on Pd/C. The racemization catalysts were combined in one pot with an immobilized lipase to perform dynamic kinetic resolution of chiral amines. High yields (up to 88%) of essentially enantiopure amides were obtained in a single step. The chemo-enzymatic catalyst system proved to be stable and could be reused without losing the initial activity.
- Parvulescu, Andrei N.,Jacobs, Pierre A.,De Vos, Dirk E.
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p. 2034 - 2043
(2008/02/03)
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- Asymmetric reduction of oxime ethers promoted by chiral spiroborate esters with an O3BN framework
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Enatioselective reduction of oxime ethers promoted by chiral spiroborate esters with an O3BN framework is reported for the first time. In the presence of (R,S)-1, 11 aralkyloxime ethers are reduced by borane-THF at 0-5 °C to give (S)-1-aralkylamine in high yield and excellent enatiomeric excess (up to 98% ee). Influence of reaction conditions on the enantioselectivity of the reduction is investigated, and a possible mechanism of the catalytic reduction is suggested.
- Chu, Yunbo,Shan, Zixing,Liu, Dejun,Sun, Nannan
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p. 3998 - 4001
(2007/10/03)
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- Resolution of 1-arylalkylamines with 3-O-hydrogen phthalate glucofuranose derivatives: Role of steric bulk in a family of resolving agents
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The development of three new acidic resolving agents which are hydrogen phthalates of 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose 1, 1,2:5,6-di-O-cyclohexylidene-α-d-glucofuranose 2 and 1,2-O- cyclohexylidene-5,6-O-diphenylmethylidene-α-d-glucofuranose 3 is shown for the resolution of 1-arylalkylamines 7a-k. The salts between 1, 2 and (RS)-1-arylalkylamines 7a-k selectively crystallize 1?(S) 7a-j and 2?(S) 7a-h salts, allowing us to recover the corresponding bases (S) 7a-j and (S) 7a-h, respectively, in good yield and enantiomeric excess (73-95% ee). Whereas, the salts between 3 and (RS)-1-arylalkylamines 7a-c,g-i,k selectively crystallize 3?(S)-7a-c,g-i salts to recover the corresponding bases (S)-7a-c,g-i in poor enantiomeric excess (4-35% ee). The difference between the resolving ability of 1 and 2 for 1-arylalkylamines 7a-h is very slight, but there is considerable difference compared to ortho-substituted 1-arylalkylamines 7i and 7j. The role of substituents on a family of resolving agents 1, 2 and 3 is also discussed to interpret their resolving ability.
- Mereyala, Hari Babu,Koduru, Sreenivasulu Reddy,Cheemalapati, Venkata Narasimhaji
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p. 259 - 267
(2007/10/03)
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- Selective diethylzinc reduction of imines in the presence of ketones catalyzed by Ni(acac)2
-
(Chemical Equation Presented) A selective reduction method of an electronically deficient imine in the presence of ketone was developed by employing Et2Zn and 5 mol % of Ni(acac)2. The method was applied in the reduction of SS-tert-butanesulfinyl ketimines 1 to afford amines 2 in 23-92% yields and 73:27 to 98:2 diastereoselectivities. A plausible mechanism was proposed on the basis of an NMR study.
- Xiao, Xue,Wang, Haowei,Huang, Zhiyan,Yang, Jun,Bian, Xiaoxia,Qin, Yong
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p. 139 - 142
(2007/10/03)
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- Optical resolution reagent and manufacturing method of optically active amines that uses it
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PROBLEM TO BE SOLVEDTo provide an effective reagent for optical resolution which produce an optically active amines by resolving the (+/-)-amines and the method for producing the optically active amines characterized by using the same reagent. SOLUTION The O-alkylthiophosphoric acid represented as the following formula (1) is effective for the optical resolution of various amines.
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Page/Page column 19-20
(2008/06/13)
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- Resolution of 1-arylalkylamines with 6-(1,2:3,4-di-O-isopropylidene- α-D-galactopyranosyl)hydrogen phthalate
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The resolving ability of a new acidic resolving agent, the hydrogen phthalate of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose 1, against various 1-arylalkylamines 2a-k is described. Treatment of 1 with amines 2a-f to obtain diastereomeric salts 1·(S)2a-f in 2-propanol allowing the corresponding (S)-amines 2a-f to be recovered in good yield and 61-89% ee. Recrystallization in dichloromethane/hexane, and regeneration gave the amines in enhanced enantiomeric purity (>98% ee). 1 resolved 1-phenylpropylamine 2f in high enantiomeric purity (99% ee) than 1-phenylethylamine 2g (11% ee) and o- and m-methoxy 2h-i, o-chloro-2j and p-fluoro-2k substituted 1-arylamines (11-19% ee). A possible chiral recognition mechanism based on the ability of 1 to exist in two conformations is described.
- Mereyala, Hari Babu,Fatima, Liyakat,Pola, Pallavi
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p. 585 - 587
(2007/10/03)
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- A new hydrogen-bonding motif for chiral recognition in the diastereomeric salts of racemic 1-phenylethylamine derivatives with enantiopure O-ethyl phenylphosphonothioic acid
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(Chemical Equation Presented) An enantiopure phosphonothioic acid showed a unique and superior chiral recognition ability, arising from its P-stereogenicity, for racemic 1-phenylethylamine derivatives through diastereomeric crystallization. Spherical molecular clusters, associated by hydrogen bonds and CH/π interactions, aggregated with high symmetry in the less-soluble diastereomeric salts.
- Kobayashi, Yuka,Morisawa, Fumi,Saigo, Kazuhiko
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p. 4227 - 4230
(2007/10/03)
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- Highly Enantioselective Hydrogen-Transfer Reductive Amination: Catalytic Asymmetric Synthesis of Primary Amines
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Ammonium formate is the hydrogen source in the catalytic asymmetric reductive amination of ketones presented here (Leuckart-Wallach-type reaction). The reaction proceeds smoothly in methanol in the presence of Ir, Rh, and Ru catalysts. Primary amines were obtained as products in good yields with high enantioselectivities after hydrolytic workup when [((R)-tol-binap) RuCl 2] was used as the catalyst (see scheme). R1, R 2=alkyl, aryl.
- Kadyrov, Renat,Riermeier, Thomas H.
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p. 5472 - 5474
(2007/10/03)
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- Process for preparing optically active amines and optically active carboxylic acids, and intermediates for preparation
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Disclosed is a process for preparing an optically active 1-aryl- or 2-aryl-alkylamines of formulas Ia, Ib and Ic with high optical purity and high yield. The process uses an optically active 1- or 2-naphthylglycolic acid of the general formula II as a resolving agent. Also disclosed is a process for praparing an optically active 1- or 2-naphthylglycolic acid of formula II using an optically active 1-aryl- or 2-aryl-alkylamines of formulas Ia, Ib and Ic as the resolving agents
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- An efficient and mild ruthenium-catalyzed racemization of amines: Application to the synthesis of enantiomerically pure amines
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An efficient and mild Ru-catalyzed racemization of amines under transfer hydrogenation conditions is reported. A significant advantage of this new procedure is that the ruthenium hydrogen transfer catalysts allow high functional group tolerance. Interestingly, both primary and secondary amines were efficiently racemized under these conditions. We also report on the combination of this new amine racemization with an enzymatic kinetic resolution of primary amines.
- Pàmies, Oscar,éll, Alida H.,Samec, Joseph S.M.,Hermanns, Nina,B?ckvall, Jan-E.
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p. 4699 - 4702
(2007/10/03)
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- Catalytic asymmetric hydroboration/amination and alkylamination with rhodium complexes of 1,1′-(2-diarylphosphino-1-naphthyl)isoquinoline
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Catecholboronate esters formed by asymmetric hydroboration of arylalkenes are not directly converted to amines by reaction with hydroxylamine-O-sulfonic acid. Prior conversion to a trialkylborane by reaction with ZnEt2 or MeMgCl permits a subsequent amination reaction to occur with essentially complete retention of configuration, leading to a range of primary α-arylalkylamines in up to 97% enantiomeric excess (ee). Secondary, but not tertiary amines may be formed by a related pathway when in situ generated alkylchloramines are employed as the aminating agent. The catalytic asymmetric hydroboration, β-alkylation and amination steps may be combined in a single stage. Overall, this provides a practical procedure for the synthesis of enantiomerically enriched arylamines, exemplified inter alia by the synthesis of (S)-1,2,3,4-tetrahydro-1-naphthylamine in 95-97% ee and of (R)-N-(cyclohexyl)-1′-(4-methoxyphenyl)ethylamine in 93 % ee.
- Fernandez, Elena,Maeda, Kenji,Hooper, Mark W.,Brown, John M.
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p. 1840 - 1846
(2007/10/03)
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- A high-performance, tailor-made resolving agent: Remarkable enhancement of resolution ability by introducing a naphthyl group into the fundamental skeleton1
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A novel resolving agent, 2-naphthylglycolic acid (2-NGA), was designed for p-substituted 1-arylethylamines on the basis of the consideration that a rigid and large naphthyl group would be favorable for the close packing of supramolecular hydrogen-bond sheets formed between the carboxy groups of 2-NGA and the amino groups of p-substituted 1-arylethylamines. Racemic 2-NGA was readily available from commercially available raw materials, and both enantiopure forms could be obtained by simple diastereomeric resolution with enantiopure 1-phenyl-ethylamine. Thus-prepared enantiopure 2-NGA was found to have an excellent resolution ability not only for p-substituted 1-arylethylamines, but also for a wide variety of chiral primary amines. X-Ray crystallographic analyses of the less- and more-soluble diastereomeric salts revealed that this excellent resolution ability of 2-NGA arose from the formation of a supramolecular hydrogen-bond sheet with the primary amine, as we had expected, and also from the possible achievement of an infinite chain of CH... π interaction between its naphthyl group and the aromatic group of the amine, which was formed in the hydrophobic region of the supramolecular hydrogen-bond sheet.
- Kinbara, Kazushi,Harada, Yoshiko,Saigo, Kazuhiko
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p. 1339 - 1347
(2007/10/03)
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- Design and SAR of novel potassium channel openers targeted for urge urinary incontinence. 1. N-cyanoguanidine bioisosteres possessing in vive bladder selectivity
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A structurally novel series of adenosine 5'-triphosphate-sensitive potassium (K(ATP)) channel openers is described. As part of our efforts directed toward identifying novel, bladder-selective potassium channel openers (KCOs) targeted for urge urinary incontinence (UUI), we found that bioisosteric replacement of the N-cyanoguanidine moiety of pinacidil (1, Figure 1) with a diaminocyclobutenedione template afforded squaric acid analogue 2, the prototype of a novel series of K(ATP) channel openers with unique selectivity for bladder smooth muscle in vive. Further modification of the heterocyclic ring to give substituted aryl derivatives (3) afforded potent KCOs that possessed the desired detrusor selectivity when administered orally. The effects of these potassium channel agonists on bladder contractile function was studied in vitro using isolated rat detrusor strips. Potent relaxants were evaluated in vive in a rat model of bladder instability. Lead compounds were evaluated concomitantly in normotensive rats for their effects on mean arterial blood pressure (MAP) and heart rate as a measure of in vive bladder selectivity. (R)-4-[3,4-Dioxo-2-(1,2,2-trimethyl- propylamino)-cyclobut-1-enyαmino]-3-ethyl-benzonitrile (79) met our potency and selectivity criteria and represents an attractive development candidate for the treatment of UUI. Electrophysiological studies using isolated rat bladder detrusor myocytes have demonstrated that compound 79 produces significant hyperpolarization which is glyburide-reversed, thus consistent with the activation of K(ATP). The design, synthesis, structure-activity relationships (SAR), and pharmacological activity associated with this series of novel KCOs will be discussed.
- Butera, John A.,Antane, Madelene M.,Antane, Schuyler A.,Argentieri, Thomas M.,Freeden, Chris,Graceffa, Russell F.,Hirth, Bradford H.,Jenkins, Douglas,Lennox, Joseph R.,Matelan, Edward,Norton, N. Wesley,Quagliato, Dominick,Sheldon, Jeffrey H.,Spinelli, Walter,Warga, Dawn,Wojdan, Alexandra,Woods, Morgan
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p. 1187 - 1202
(2007/10/03)
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- (2-naphthyl)glycolic acid: A tailored resolving agent for p-substituted 1-arylethylamines
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A tailored resolving agent for p-substituted l-arylethylamines, which was designed on the basis of a criterion derived from our crystal-structure study, namely that the racemate and the resolving agent should have similar molecular lengths, is described. The designed enantiopure (2- naphthyl)glycolie acid (2-NGA) showed excellent resolving ability for a wide variety of p-substituted l-arylethylamines.
- Kinbara, Kazushi,Harada, Yoshiko,Saigo, Kazuhiko
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p. 2219 - 2222
(2007/10/03)
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- Reduction of amines with isopropylidene glycerol hydrogen phthalate
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The hydrogen phthalate of isopropylidene glycerol has been recently described as an efficient resolving agent of 1-arylethylamines. In order to gain more information on its versatility and to develop a rationale which accounts for its effectiveness, further 1-arylethylamines and other racemic amines were subjected to the same resolution process. A preliminary qualitative analysis of the results reported herein allows to identify some structural features of the aminic substrates conditioning the feasibility of the resolution.
- Pallavicini, Marco,Valoti, Ermanno,Villa, Luigi,Piccolo, Oreste
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p. 1069 - 1073
(2007/10/03)
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- Asymmetric recognition of 1-arylethylamines by (R)-phenylglycyl-(R)-phenylglycine and its mechanism
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An unprotected dipeptide, (R)-phenylglycyl-(R)-phenylglycine, which is insoluble in water, was shown to be an excellent resolving reagent for racemic 1-arylethylamines. By simply stirring the mixture of the dipeptide and racemic 1-phenylethylamine in presence of water, asymmetric recognition occurred to give a salt of (S)-1-phenylethylamine (95% ee) and the dipeptide. X-Ray crystallographic study of the salt elucidated the crystal structure of the diastereomeric salt, where hydrogen bonding and hydrophobic interaction between the dipeptide and amines play important roles in the construction of layers.
- Akazome, Motohiro,Matsuno, Hirozumi,Ogura, Katsuyuki
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p. 2331 - 2336
(2007/10/03)
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- Catalytic asymmetric hydroboration-amination
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A one-pot asymmetric synthesis of primary amines from vinylarenes via catalytic hydroboration is described.
- Fernandez, Elena,Hooper, Mark W.,Knight, Frances I.,Brown, John M.
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p. 173 - 174
(2007/10/03)
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- Asymmetric synthesis of amines using a chiral, non-racemic, benzylidene sulfinamide derived from a recoverable precursor
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The homochiral cyclic sulfinamide S(S)R-(+)-1 has been employed for the asymmetric synthesis of α-substituted benzylamines via the benzylidene sulfinamides R(S)R-(-)-4. Following diastereoselective reduction and hydrolysis S(S)R-(+)-1 can be recycled in one step from the sulfinic acid 11. The addition of zinc(II) bromide reverses the diastereoselectivity of the diisobutylaluminium hydride (DIBAL) reduction of the substrates 4. The same reversal is not observed in the reactions of analogues lacking an amide side chain. In one case the required benzylidene sulfinamide exists in the form of an enamine 15, the X-ray crystallographic structure of which is also featured. A second approach to chiral amines, via the addition of Grignard reagents to sulfinylamines derived from S(S)R-(+)-1, is also described.
- Hose, David R. J.,Mahon, Mary F.,Molloy, Kieran C.,Raynham, Tony,Wills, Martin
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p. 691 - 703
(2007/10/03)
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- Enantiomerically pure amines by a new method: Biotransformation of oxalamic esters using the lipase from Candida antarctica
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Octyl oxalamic esters of 1-phenylethylamine and substituted 1-phenylethylamines are kinetically resolved with high stereoselectivity by lipase B from Candida antarctica.
- Chapman, Daniel T.,Crout, David H. G.,Mahmoudian, Mahmoud,Scopes, David I. C.,Smith, Paul W.
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p. 2415 - 2416
(2007/10/03)
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- HIV PROTEASE INHIBITORS
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Peptide mimics, having a constrained peptide backbone conformation, are HIV protease inhibitors. A compound of this invention is, for example, 3-Benzyl-5(alaninyl-1-aminoethyl)-2,3,6,7-tetrahydro-N-azepinyl-2-propionyl-valinyl-valinyl methyl ester.
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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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