- REACTIONS OF METHYLCOPPER AND CHIRAL ORGANOCUPRATES WITH 1-NITRO-2-PHENYLETHENE AND OF LITHIUM DIMETHYLCUPRATE WITH METHYL 3(NITROPHENYL)PROPENOATES
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Organocopper compounds like methylcopper, lithium dimethylcuprate, chiral lithium methyl-(S)-2(1-dimethylaminoethyl)-phenylcuprate and lithium menthoxy(methyl)cuprate react with 1-nitro-2-phenylethene to give the conjugate addition product 1-nitro-2-phenylpropane in moderate yields.In the reaction with lithium methyl-(S)-2(1-dimethylaminoethyl)phenylcuprate 2percent asymmetric induction was obtained.The reaction between lithium dimethylcuprate and methyl 3(4-nitrophenyl)propenoate gave the corresponding azoxy compound and no conjugate addition product, while methyl 3(3-nitrophenyl)propenoate gave some conjugate addition.
- Hansson, A.-T.,Nilsson, M.
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- Biocatalysis with thermostable enzymes: Structure and properties of a thermophilic 'ene'-reductase related to old yellow enzyme
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We report the crystal structure of a thermophilic "ene" reductase (TOYE) isolated from Thermoanaerobacter pseudethanolicus E39. The crystal structure reveals a tetrameric enzyme and an active site that is relatively large compared to most other structurally determined and related Old Yellow Enzymes. The enzyme adopts higher order oligomeric states (octamers and dodecamers) in solution, as revealed by sedimentation velocity and multiangle laser light scattering. Bead modelling indicates that the solution structure is consistent with the basic tetrameric structure observed in crystallographic studies and electron microscopy. TOYE is stable at high temperatures (T m > 70°C) and shows increased resistance to denaturation in water-miscible organic solvents compared to the mesophilic Old Yellow Enzyme family member, pentaerythritol tetranitrate reductase. TOYE has typical ene-reductase properties of the Old Yellow Enzyme family. There is currently major interest in using Old Yellow Enzyme family members in the preparative biocatalysis of a number of activated alkenes. The increased stability of TOYE in organic solvents is advantageous for biotransformations in which water-miscible organic solvents and biphasic reaction conditions are required to both deliver novel substrates and minimize product racemisation.
- Adalbjoernsson, Bjoern V.,Toogood, Helen S.,Fryszkowska, Anna,Pudney, Christopher R.,Jowitt, Thomas A.,Leys, David,Scrutton, Nigel S.
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- Asymmetric bioreduction of activated C=C bonds using Zymomonas mobilis NCR enoate reductase and old yellow enzymes OYE 1-3 from yeasts
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The asymmetric bioreduction of C=C-bonds bearing an electron-withdrawing group, such as an aldehyde, ketone, imide, nitro, carboxylic acid, or ester moiety by a novel enoate reductase from Zymomonas mobilis and Old Yellow Enzymes OYE 1-3 from yeasts furnished the corresponding saturated products in up to >99%ee. Depending on the substrate type, stereocontrol was achieved by variation of the substrate structure, by switching the (E/Z) geometry of the alkene or by choice of the appropriate enzyme. This substrate- or enzyme-based stereocontrol allowed access to the opposite enantiomeric products. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Hall, Melanie,Stueckler, Clemens,Hauer, Bernhard,Stuermer, Rainer,Friedrich, Thomas,Breuer, Michael,Kroutil, Wolfgang,Faber, Kurt
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- Chemoselective and enantioselective transfer hydrogenation of Β, Β-disubstituted nitroalkenes catalyzed by a water-insoluble chiral diaminerhodium complex in water
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Asymmetric transfer hydrogenation of Β, Β-disubstituted nitroalkenes catalyzed by a chiral diaminerhodium complex in combination with HCO2NaHCO2H as a hydrogen source in water was successfully realized with high reactivity, excellent chemoselectivity and good enantioselectivity. The metal precursor and pH value of the aqueous solution have a large influence on the reactivity and chemoselectivity. The substituents on the benzene rings and the sulfonyl groups of TsDPEN have significant effects on the enantioselectivity. This catalytic asymmetric transformation is one of the most practical pathways to obtain optically active nitroalkanes.
- Tang, Yuanfu,Xiang, Jing,Cun, Linfeng,Wang, Yuqin,Zhu, Jin,Liao, Jian,Deng, Jingen
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- A robust and stereocomplementary panel of ene-reductase variants for gram-scale asymmetric hydrogenation
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We report an engineered panel of ene-reductases (ERs) from Thermus scotoductus SA-01 (TsER) that combines control over facial selectivity in the reduction of electron deficient C[dbnd]C double bonds with thermostability (up to 70 °C), organic solvent tolerance (up to 40 % v/v) and a broad substrate scope (23 compounds, three new to literature). Substrate acceptance and facial selectivity of 3-methylcyclohexenone was rationalized by crystallisation of TsER C25D/I67T and in silico docking. The TsER variant panel shows excellent enantiomeric excess (ee) and yields during bi-phasic preparative scale synthesis, with isolated yield of up to 93 % for 2R,5S-dihydrocarvone (3.6 g). Turnover frequencies (TOF) of approximately 40 000 h?1 were achieved, which are comparable to rates in hetero- and homogeneous metal catalysed hydrogenations. Preliminary batch reactions also demonstrated the reusability of the reaction system by consecutively removing the organic phase (n-pentane) for product removal and replacing with fresh substrate. Four consecutive batches yielded ca. 27 g L?1 R-levodione from a 45 mL aqueous reaction, containing less than 17 mg (10 μM) enzyme and the reaction only stopping because of acidification. The TsER variant panel provides a robust, highly active and stereocomplementary base for further exploitation as a tool in preparative organic synthesis.
- Nett, Nathalie,Duewel, Sabine,Schmermund, Luca,Benary, Gerrit E.,Ranaghan, Kara,Mulholland, Adrian,Opperman, Diederik J.,Hoebenreich, Sabrina
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- Asymmetrie reduction of activated alkenes by pentaerythritol tetranitrate reductase: Specificity and control of stereochemical outcome by reaction optimisation
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We show that pentaerythritol tetranitrate reductase (PETNR), a member of the 'ene' reductase old yellow enzyme family, catalyses the asymmetric reduction of a variety of industrially relevant activated α,β-unsaturated alkenes including enones, enals, maleimides and nitroalkenes. We have rationalised the broad substrate specificity and stereochemical outcome of these reductions by reference to molecular models of enzyme-substrate complexes based on the crystal complex of the PETNR with 2cyclohexenone 4a. The optical purity of products is variable (49-99% ee), depending on the substrate type and nature of substituents. Generally, high enantioselectivity was observed for reaction products with stereogenic centres at Cβ (>99% ee). However, for the substrates existing in two isomeric forms (e.g., citral 11a or nitroalkenes 18-19a), an enantio-divergent course of the reduction of E/Z-forms may lead to lower enantiopurities of the products. We also demonstrate that the poor optical purity obtained for products with stereogenic centres at Ca is due to non-enzymatic racemisation. In reactions with ketoisophorone 3a we show that product racemisation is prevented through reaction optimisation, specifically by shortening reaction time and through control of solution pH. We suggest this as a general strategy for improved recovery of optically pure products with other biocatalytic conversions where there is potential for product racemisation.
- Fryszkowska, Anna,Toogood, Helen,Sakuma, Michiyo,Gardiner, John M.,Stephens, Gill M.,Scrutton, Nigel S.
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- Nitroalkene reduction in deep eutectic solvents promoted by BH3NH3
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Deep eutectic solvents (DESs) have gained attention as green and safe as well as economically and environmentally sustainable alternative to the traditional organic solvents. Here, we report the combination of an atom-economic, very convenient and inexpensive reagent, such as BH3NH3, with bio-based eutectic mixtures as biorenewable solvents in the synthesis of nitroalkanes, valuable precursors of amines. A variety of nitrostyrenes and alkyl-substituted nitroalkenes, including α- and β-substituted nitroolefins, were chemoselectively reduced to the nitroalkanes, with an atom economy-oriented, simple and convenient experimental procedure. A reliable and easily reproducible protocol to isolate the product without the use of any organic solvent was established, and the recyclability of the DES mixture was successfully investigated.
- Benaglia, Maurizio,Boselli, Monica Fiorenza,Faverio, Chiara,Gonzalez, Patricia Camarero,Puglisi, Alessandra
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supporting information
p. 1041 - 1047
(2021/05/17)
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- Metal-Free Deoxygenation of Chiral Nitroalkanes: An Easy Entry to α-Substituted Enantiomerically Enriched Nitriles
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A metal-free, mild and chemodivergent transformation involving nitroalkanes has been developed. Under optimized reaction conditions, in the presence of trichlorosilane and a tertiary amine, aliphatic nitroalkanes were selectively converted into amines or nitriles. Furthermore, when chiral β-substituted nitro compounds were reacted, the stereochemical integrity of the stereocenter was maintained and α-functionalized nitriles were obtained with no loss of enantiomeric excess. The methodology was successfully applied to the synthesis of chiral β-cyano esters, α-aryl alkylnitriles, and TBS-protected cyanohydrins, including direct precursors of four active pharmaceutical ingredients (ibuprofen, tembamide, aegeline and denopamine).
- Pirola, Margherita,Faverio, Chiara,Orlandi, Manuel,Benaglia, Maurizio
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p. 10247 - 10250
(2021/06/18)
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- Radical Capture at Nickel(II) Complexes: C-C, C-N, and C-O Bond Formation
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The dinuclear β-diketiminato NiII tert-butoxide {[Me3NN]Ni}2(μ-OtBu)2 (2), synthesized from [Me3NN]Ni(2,4-lutidine) (1) and di-tert-butylperoxide, is a versatile precursor for the synthesis of a series of NiII complexes [Me3NN]Ni-FG (FG = functional group) to illustrate C-C, C-N, and C-O bond formation at NiII via radical capture. {[Me3NN]Ni}2(μ-OtBu)2 reacts with nitromethane, alkyl and aryl amines, acetophenone, benzamide, ammonia, and phenols to deliver the corresponding mono- or dinuclear [Me3NN]Ni-FG species (FG = O2NCH2, R-NH, ArNH, PhC(O)NH, PhC(O)CH2, NH2, and OAr). Many of these NiII complexes are capable of capturing the benzylic radical PhCH(?)CH3 to deliver the corresponding PhCH(FG)CH3 products featuring C-C, C-N, or C-O bonds. Density functional theory studies shed light on the mechanism of these transformations and suggest two competing pathways that depend on the nature of the functional groups. These radical capture reactions at [NiII]-FG complexes outline key C-C, C-N, and C-O bond forming steps, foreshadowing families of nickel radical relay catalysts.
- Bakhoda, Abolghasem Gus,Bertke, Jeffery A.,Figula, Bryan C.,Greene, Christine,Warren, Timothy H.,Wiese, Stefan
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supporting information
p. 1710 - 1718
(2020/07/13)
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- Light-Enabled Enantiodivergence: Stereospecific Reduction of Activated Alkenes Using a Single Organocatalyst Enantiomer
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Light-enabled enantiodivergence is demonstrated in which the alkene substrate configuration is manipulated (E → Z) prior to organocatalytic reduction with a chiral thiourea and Hantzsch ester. This allows stereodivergent reduction to be regulated at the substrate level with high fidelity and mitigates the need for a second, enantiomeric catalyst (up to 93:07 and 95:5 er). The synthetic utility of this strategy has been demonstrated in the synthesis of the weight-loss drug (R)-Lorcaserin (Belviq) and a potent AMPA modulator.
- Hostmann, Theresa,Molloy, John J.,Bussmann, Kathrin,Gilmour, Ryan
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supporting information
p. 10164 - 10168
(2019/12/24)
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- Autoinductive conversion of α,α-diiodonitroalkanes to amides and esters catalysed by iodine byproducts under O2
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Studies to convert nitroalkanes into amides and esters using I2 and O2 revealed in situ-generated iodine species facilitate the homolytic C-I bond cleavage of α,α-diiodonitroalkanes, arguably in an autoinductive or autocatalytic manner. Consequently, we devised a rapid and economical I2/O2-based method to synthesise sterically hindered esters directly from primary nitroalkanes.
- Li, Jing,Lear, Martin J.,Hayashi, Yujiro
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supporting information
p. 6360 - 6363
(2018/06/21)
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- New insights into the catalytic reduction of aliphatic nitro compounds with hypophosphites under ultrasonic irradiation
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This work describes an efficient process for the reduction of nitro compounds to the corresponding amines with a catalytic amount of Pd/C (0.6 mol%), and a mixture of sodium hypophosphite and hypophosphorous acid as a reducing agent in H2O/2-MeTHF at 60 °C. The reaction was optimized under silent conditions. The conditions for the in situ production of H2 using the mixture NaH2PO2/H3PO2 were studied. The influence of ultrasonic activation was investigated both in terms of efficiency and kinetics. The reaction was shown to be efficient in water, at 70 °C with a quantitative conversion and a maximal yield in only 15 min thanks to the ultrasonic activation. Finally, ultrasound was proved to act as a physical agent of phase transfer.
- Letort,Lejeune,Kardos,Métay,Popowycz,Lemaire,Draye
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supporting information
p. 4583 - 4590
(2017/10/13)
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- Enantioselective iridium-catalyzed hydrogenation of β,β-disubstituted nitroalkenes
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An iridium complex with a newly prepared chiral spiro amino-phosphine ligand efficiently catalyzed the hydrogenation of both β-aryl-β-methyl-nitroalkenes and β-alkyl-β-methyl-nitroalkenes to the corresponding saturated nitroalkanes, which represents the f
- Yu, Yan-Bo,Cheng, Lei,Li, Yi-Pan,Fu, Yue,Zhu, Shou-Fei,Zhou, Qi-Lin
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supporting information
p. 4812 - 4815
(2016/04/09)
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- Reversible modulation of the activity of thiourea catalysts with anions: A simple approach to switchable asymmetric catalysis
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Leveraging the anion binding properties of thioureas, we show that the activity of known well-performing chiral catalysts can be reduced by coordinating anions (e.g. chloride) and restored by anion metatheses. Three benchmark enantioselective transformati
- Foli, Giacomo,D'Elia, Cecilia Sasso,Fochi, Mariafrancesca,Bernardi, Luca
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p. 66490 - 66494
(2016/08/02)
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- Substrate Scope Evaluation of the Enantioselective Reduction of β-Alkyl-β-arylnitroalkenes by Old Yellow Enzymes 1-3 for Organic Synthesis Applications
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The substrate scope of the old yellow enzyme catalyzed reduction of β-alkyl-β-arylnitroalkenes is investigated. Compounds bearing either alkyl chains of increasing length at the carbon atom in position β to the nitro group or different substituents on the aromatic ring are prepared and submitted to bioreduction, to define the synthetic potential of this enantioselective reaction in the preparation of chiral fine chemicals. The versatility of the resulting nitroalkanes as chiral building blocks is shown by reducing the nitro group into a primary amine and by converting it into a carboxylic acid moiety by Meyer reaction. An "explosion" of chiral products can be observed by combining the highly enantioselective ene-reductase-mediated reduction of nitroalkenes with the chemical versatility of the nitro group.
- Bertolotti, Mattia,Brenna, Elisabetta,Crotti, Michele,Gatti, Francesco G.,Monti, Daniela,Parmeggiani, Fabio,Santangelo, Sara
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p. 577 - 583
(2016/02/23)
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- Metal-Templated Design: Enantioselective Hydrogen-Bond-Driven Catalysis Requiring only Parts-per-Million Catalyst Loading
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Based on a metal-templated approach using a rigid and globular structural scaffold in the form of a bis-cyclometalated octahedral iridium complex, an exceptionally active hydrogen-bond-mediated asymmetric catalyst was developed and its mode of action inve
- Xu, Weici,Arieno, Marcus,L?w, Henrik,Huang, Kaifang,Xie, Xiulan,Cruchter, Thomas,Ma, Qiao,Xi, Jianwei,Huang, Biao,Wiest, Olaf,Gong, Lei,Meggers, Eric
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supporting information
p. 8774 - 8780
(2016/08/02)
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- Two "classical" Old Yellow Enzymes from Chryseobacterium sp. CA49: Broad substrate specificity of Chr-OYE1 and limited activity of Chr-OYE2
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Two putative Old Yellow Enzyme (OYE) homologues, Chr-OYE1 and Chr-OYE2, were identified from the genome of Chryseobacterium sp. CA49 as new members of the "classical" subfamily. Chr-OYE1 and Chr-OYE2 were most closely related to the SYE4 from Shewanella oneidensis and NerA from Agrobacterium radiobacter with 41% and 45% identity, respectively. Both enzymes were expressed in Escherichia coli in soluble form, but their catalytic abilities as ene-reductases were quite different. Among the 19 substrate tested, Chr-OYE1 could catalyze the reduction of 18 of them including an ynone with excellent stereoselectivity for several prochiral ones, and its specific activity was roughly 1100-fold high than Chr-OYE2, which only catalyzed 3 of the substrates. After restoring the conserved tyrosine, Chr-OYE2 remained the same substrate spectrum, but showed significantly enhanced activity and stereoselectivity.
- Pei, Xiao-Qiong,Xu, Meng-Yu,Wu, Zhong-Liu
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- The organic-synthetic potential of recombinant Ene reductases: Substrate-Scope Evaluation and Process Optimization
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In this study an evaluation of the synthetic potential of a broad range of recombinant ene reductases was performed. In detail, a library of 23 ene reductases was used to screen the C=C reduction of 21 activated alkenes from different compound classes as substrates. The chosen set of substrates comprises nitroalkenes with an aryl substituent at the β-position and a methyl substituent at the α- or β-position, α,β-unsaturated carboxylic acids and their esters with and without substituents at the β-position, a range of cyclic α,β-unsaturated ketones with different ring sizes and substitution patterns and one α,β-unsaturated boronic acid. After we obtained insight into the substrate scope, several biotransformations were prioritised and further investigated in a screening of 41 reaction parameters (which included chaotropic and kosmotropic salts, polyols, buffer solutions, amino acids and organic solvents) towards their impact on the activity and enantioselectivity of the applied ene reductases. Under the optimised conditions, selected reduction processes were performed on an increased lab scale (up to 30 mL) with up to 10% substrate concentration, which led in general to both high conversion and (if chiral products were formed) enantioselectivity. Comprehensive screening: A detailed screening of 23 recombinant ene reductases for the reduction of 21 activated alkenes is performed as well as a subsequent study of the influence of 41 reaction parameters towards the enzyme activity and selectivity of selected reactions. In addition, a range of biocatalytic reductions on an increased laboratory scale are performed with substrate concentrations between 5 and 100 gL-1. EWG=Electron-withdrawing group.
- Re?, Tina,Hummel, Werner,Hanlon, Steven P.,Iding, Hans,Gr?ger, Harald
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p. 1302 - 1311
(2015/04/27)
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- Biocatalytic asymmetric alkene reduction: Crystal structure and characterization of a double bond reductase from Nicotiana tabacum
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The application of biocatalysis for the asymmetric reduction of activated C=C is a powerful tool for the manufacture of high-value chemical commodities. The biocatalytic potential of "-ene" reductases from the Old Yellow Enzyme (OYE) family of oxidoreductases is well-known; however, the specificity of these enzymes toward mainly small molecule substrates has highlighted the need to discover "-ene" reductases from different enzymatic classes to broaden industrial applicability. Here, we describe the characterization of a flavin-free double bond reductase from Nicotiana tabacum (NtDBR), which belongs to the leukotriene B4 dehydrogenase (LTD) subfamily of the zinc-independent, medium chain dehydrogenase/reductase superfamily of enzymes. Using steady-state kinetics and biotransformation reactions, we have demonstrated the regio- and stereospecificity of NtDBR against a variety of α,β-unsaturated activated alkenes. In addition to catalyzing the reduction of typical LTD substrates and several classical OYE-like substrates, NtDBR also exhibited complementary activity by reducing non-OYE substrates (i.e., reducing the exocyclic C=C double bond of (R)-pulegone) and in some cases showing an opposite stereopreference in comparison with the OYE family member pentaerythritol tetranitrate (PETN) reductase. This serves to augment classical OYE "-ene" reductase activity and, coupled with its aerobic stability, emphasizes the potential industrial value of NtDBR. Furthermore, we also report the X-ray crystal structures of the holo-, binary NADP(H)-bound, and ternary [NADP+ and 4-hydroxy-3-methoxycinnamaldehyde (9a)-bound] NtDBR complexes. These will underpin structure-driven site-saturated mutagenesis studies aimed at enhancing the reactivity, stereochemistry, and specificity of this enzyme.
- Mansell, David J.,Toogood, Helen S.,Waller, John,Hughes, John M.X.,Levy, Colin W.,Gardiner, John M.,Scrutton, Nigel S.
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p. 370 - 379
(2013/08/25)
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- Rh-catalyzed highly enantioselective hydrogenation of nitroalkenes under basic conditions
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Go catalytic! A highly enantioselective hydrogenation of β,β-disubstituted nitroalkenes and isomeric mixtures of nitroalkenes by using a Rh/DuanPhos catalytic system under basic conditions has furnished a convenient approach to β-chiral nitroalkanes, whic
- Li, Shengkun,Huang, Kexuan,Zhang, Jiwen,Wu, Wenjun,Zhang, Xumu
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p. 10840 - 10844
(2013/09/02)
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- A novel chiral bisphosphine-thiourea ligand for asymmetric hydrogenation of β,β-disubstituted nitroalkenes
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A novel chiral bisphosphine-thiourea ligand was developed and applied in the highly enantioselective hydrogenation of β,β-disubstituted nitroalkenes (up to 99% yield and 99% ee). With low catalytic loading (0.25 mol %), 98% ee and 98% conversion were obta
- Zhao, Qingyang,Li, Shengkun,Huang, Kexuan,Wang, Rui,Zhang, Xumu
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supporting information
p. 4014 - 4017
(2013/09/02)
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- Enantio- and regioselective conjugate addition of organometallic reagents to linear polyconjugated nitroolefins
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The copper-catalysed conjugate addition of trialkylaluminium and dialkylzinc reagents to polyconjugated nitroolefins (nitrodiene and nitroenyne derivatives) is reported. A reversed Josiphos ligand L7 allows for the selective 1,4- or 1,6-addition with high enantioselectivities. Copyright
- Tissot, Matthieu,Alexakis, Alexandre
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supporting information
p. 11352 - 11363
(2013/09/02)
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- Asymmetric catalysis with an inert chiral-at-metal iridium complex
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The development of a chiral-at-metal iridium(III) complex for the highly efficient catalytic asymmetric transfer hydrogenation of β,β′- disubstituted nitroalkenes is reported. Catalysis by this inert, rigid metal complex does not involve any direct metal coordination but operates exclusively through weak interactions with functional groups properly arranged in the ligand sphere of the iridium complex. Although the iridium complex relies only on the formation of three hydrogen bonds, it exceeds the performance of most organocatalysts with respect to enantiomeric excess (up to 99% ee) and catalyst loading (down to 0.1 mol %). This work hints at an advantage of structurally complicated rigid scaffolds for non-covalent catalysis, which especially relies on conformationally constrained cooperative interactions between the catalyst and substrates.
- Chen, Liang-An,Xu, Weici,Huang, Biao,Ma, Jiajia,Wang, Lun,Xi, Jianwei,Harms, Klaus,Gong, Lei,Meggers, Eric
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supporting information
p. 10598 - 10601
(2013/08/23)
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- Highly enantioselective hydrogenation of β,β-disubstituted nitroalkenes
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Building the building blocks: A highly enantioselective hydrogenation of ?-aryl-?-alkyl disubstituted nitroalkenes 1 has been developed. This method results in enantiomerically pure nitroalkanes 2, which are versatile precursors for chemical synthesis.
- Li, Shengkun,Huang, Kexuan,Cao, Bonan,Zhang, Jiwen,Wu, Wenjun,Zhang, Xumu
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p. 8573 - 8576
(2012/09/10)
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- Nicotinamide-dependent Ene reductases as alternative biocatalysts for the reduction of activated alkenes
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Four NAD(P)H-dependent non-flavin ene reductases have been investigated for their ability to reduce activated C=C bonds in an asymmetric fashion by using 20 structurally diverse substrates. In comparison with flavin-dependent Old Yellow Enzyme homologues, a higher degree of electronic activation was required, because the best activities were obtained with enals and nitroalkenes rather than enones and carboxylic esters. Although FaEO from Fragaria x ananassa (strawberry) and its homologue SlEO from Solanum lycopersicum (tomato) exhibited a narrow substrate spectrum, progesterone 5β-reductase (At5β-StR) from Arabidopsis thaliana (thale cress) and leukotriene B4 12-hydroxydehydrogenase (LTB4DH/PGR) from Rattus norvegicus (rat) appear to be promising candidates, in particular for the asymmetric bioreduction of open-chain enals, nitroalkenes and α,β-unsaturated γ-butyrolactones. Competing nitro reduction and non-enzymatic Weitz-Scheffer epoxidation were largely suppressed. Electronically activated alkenes have been stereoselectively reduced by using a single-enzyme-cofactor system employing nicotinamide-dependent non-flavin ene reductases. Copyright
- Durchschein, Katharina,Wallner, Silvia,MacHeroux, Peter,Schwab, Wilfried,Winkler, Thorsten,Kreis, Wolfgang,Faber, Kurt
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p. 4963 - 4968
(2013/01/14)
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- A Site-Saturated Mutagenesis Study of Pentaerythritol Tetranitrate Reductase Reveals that Residues 181 and 184 Influence Ligand Binding, Stereochemistry and Reactivity
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We have conducted a site-specific saturation mutagenesis study of H181 and H184 of flavoprotein pentaerythritol tetranitrate reductase (PETN reductase) to probe the role of these residues in substrate binding and catalysis with a variety of α,β-unsaturated alkenes. Single mutations at these residues were sufficient to dramatically increase the enantiopurity of products formed by reduction of 2-phenyl-1-nitropropene. In addition, many mutants exhibited a switch in reactivity to predominantly catalyse nitro reduction, as opposed to C=C reduction. These mutants showed an enhancement in a minor side reaction and formed 2-phenylpropanal oxime from 2-phenyl-1-nitropropene. The multiple binding conformations of hydroxy substituted nitro-olefins in PETN reductase were examined by using both structural and catalytic techniques. These compounds were found to bind in both active and inhibitory complexes; this highlights the plasticity of the active site and the ability of the H181/H184 couple to coordinate with multiple functional groups. These properties demonstrate the potential to use PETN reductase as a scaffold in the development of industrially useful biocatalysts. Divergent evolution: A site-saturation study of PETN reductase was performed at conserved substrate binding residues H181 and H184. These residues were shown to dramatically alter the ratio of alkene versus nitro-group reduction in favour of oxime by-product formation, as summarised in the picture.
- Toogood, Helen S.,Fryszkowska, Anna,Hulley, Martyn,Sakuma, Michiyo,Mansell, David,Stephens, Gill M.,Gardiner, John M.,Scrutton, Nigel S.
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scheme or table
p. 738 - 749
(2012/02/01)
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- Readily available hydrogen bond catalysts for the asymmetric transfer hydrogenation of nitroolefins
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This paper focuses on readily accessible thiourea hydrogen bond catalysts derived from amino acids, whose steric and electronic features are modulated by their degree of substitution at the carbinol carbon center. These catalysts were applied in the asymmetric transfer hydrogenation of nitroolefins furnishing the chiral products in up to 99% yield and 86% enantiomeric excess. The proposed catalyst's mode of action is supported by mechanistic investigations.
- Schneider, Jakob F.,Lauber, Markus B.,Muhr, Vanessa,Kratzer, Domenic,Paradies, Jan
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p. 4323 - 4327
(2011/07/08)
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- CHIRAL IRIDIUM AQUA COMPLEX AND METHOD FOR PRODUCING OPTICALLY ACTIVE HYDROXY COMPOUND USING THE SAME
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The present invention provides a novel chiral iridium aqua complex which has good preservation stability, can be easily produced and enables asymmetric transfer hydrogenation in a higher yield and with higher stereoselectivity. The present invention provi
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Page/Page column 46-47
(2011/05/05)
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- Asymmetric bioreduction of alkenes using ene-reductases YersER and KYE1 and effects of organic solvents
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Asymmetric trans-bioreduction of activated alkenes by KYE1 from Kluyveromyces lactis and Yers-ER from Yersinia bercovieri, two ene-reductases from the Old Yellow Enzyme family, showed a broad substrate spectrum with a moderate to excellent degree of stereoselectivity. Both substrate- and enzyme-based stereocontrols were observed to furnish opposite stereoisomeric products. The effects of organic solvents on enzyme activity and stereoselectivity were outlined in this study, where two-phase systems hexane and toluene are shown to sustain bioreduction efficiency even at high organic solvent content.
- Yanto, Yanto,Winkler, Christoph K.,Lohr, Stephanie,Hall, Melanie,Faber, Kurt,Bommarius, Andreas S.
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supporting information; experimental part
p. 2540 - 2543
(2011/06/25)
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- Reductive biotransformation of nitroalkenes via nitroso-intermediates to oxazetes catalyzed by xenobiotic reductase A (XenA)
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A novel reductive biotransformation pathway for β,β-disubstituted nitroalkenes catalyzed by flavoproteins from the Old Yellow Enzyme (OYE) family was elucidated. It was shown to proceed via enzymatic reduction of the nitro-moiety to furnish the corresponding nitroso-alkene, which underwent spontaneous (non-enzymatic) electrocyclization to form highly strained 1,2-oxazete derivatives. At elevated temperatures the latter lost HCN via a retro-[2 + 2]-cycloaddition to form the corresponding ketones. This pathway was particularly dominant using xenobiotic reductase A, while pentaerythritol tetranitrate-reductase predominantly catalyzed the biodegradation via the Nef-pathway.
- Durchschein, Katharina,Fabian, Walter M. F.,MacHeroux, Peter,Zangger, Klaus,Trimmel, Gregor,Faber, Kurt
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p. 3364 - 3369
(2011/06/25)
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- Focused Directed Evolution of Pentaerythritol Tetranitrate Reductase by Using Automated Anaerobic Kinetic Screening of Site-Saturated Libraries
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This work describes the development of an automated robotic platform for the rapid screening of enzyme variants generated from directed evolution studies of pentraerythritol tetranitrate (PETN) reductase, a target for industrial biocatalysis. By using a 96-well format, near pure enzyme was recovered and was suitable for high throughput kinetic assays; this enabled rapid screening for improved and new activities from libraries of enzyme variants. Initial characterisation of several single site-saturation libraries targeted at active site residues of PETN reductase, are described. Two mutants (T26S and W102F) were shown to have switched in substrate enantiopreference against substrates (E)-2-aryl-1-nitropropene and α-methyl-trans-cinnamaldehyde, respectively, with an increase in ee (62 % (R) for W102F). In addition, the detection of mutants with weak activity against α,β-unsaturated carboxylic acid substrates showed progress in the expansion of the substrate range of PETN reductase. These methods can readily be adapted for rapid evolution of enzyme variants with other oxidoreductase enzymes.
- Hulley, Martyn E.,Toogood, Helen S.,Fryszkowska, Anna,Mansell, David,Stephens, Gill M.,Gardiner, John M.,Scrutton, Nigel S.
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experimental part
p. 2433 - 2447
(2011/07/08)
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- Characterization of xenobiotic reductase A (XenA): Study of active site residues, substrate spectrum and stability
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Xenobiotic reductase A (XenA) has broad catalytic activity and reduces various α,β-unsaturated and nitro compounds with moderate to excellent stereoselectivity. Single mutants C25G and C25V are able to reduce nitrobenzene, a non-active substrate for the wild type, to produce aniline. Total turnover is dominated by chemical rather than thermal instability. The Royal Society of Chemistry 2010.
- Yanto, Yanto,Yu, Hua-Hsiang,Hall, Melanie,Bommarius, Andreas S.
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scheme or table
p. 8809 - 8811
(2011/02/28)
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- The flavoprotein-catalyzed reduction of aliphatic nitro-compounds represents a biocatalytic equivalent to the Nef-reaction
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The bioreduction of aliphatic sec-nitro compounds catalyzed by purified flavoproteins from the old-yellow-enzyme family unexpectedly furnished the corresponding carbonyl compounds instead of the expected amines and thus represents a biocatalytic equivalent to the Nef-reaction. The pathway was shown to proceed via initial reduction of the nitro-group to yield the nitroso-derivative, which spontaneously tautomerized to yield the more stable oxime, which was enzymatically reduced in a second step to furnish a hydrolytically unstable imine-species, which spontaneously hydrolyzed to finally give a carbonyl compound and ammonia.
- Durchschein, Katharina,Ferreira-Da Silva, Bianca,Wallner, Silvia,MacHeroux, Peter,Kroutil, Wolfgang,Glueck, Silvia Maria,Faber, Kurt
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experimental part
p. 616 - 619
(2010/09/05)
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- The substrate spectra of pentaerythritol tetranitrate reductase, morphinone reductase, N-ethylmaleimide reductase and estrogen-binding protein in the asymmetric bioreduction of activated alkenes
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Four flavoproteins from the old yellow enzyme (OYE) family, pentaerythritol tetranitrate (PETNR) reductase, N-ethylmaleimide reductase (NEMR), morphinone reductase (MorR) and estrogen-binding protein (EBP1), exhibited a broad substrate tolerance by accepting conjugated enals, enones, imides, dicarboxylic acids and esters, as well as a nitroalkene and therefore can be employed for the asymmetric bioreduction of carbon-carbon double (C=C) bonds. In particular, morphinone reductase and estrogen-binding protein often showed a complementary stereochemical preference in comparison to that of previously investigated OYES.
- Mueller, Nicole J.,Stueckler, Clemens,Hauer, Bernhard,Baudendistel, Nina,Housden, Hazel,Bruce, Neil C.,Faber, Kurt
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experimental part
p. 387 - 394
(2010/06/11)
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- Planar-chiral thioureas as hydrogen-bond catalysts
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The synthesis of the first enantiopure planar-chiral thiourea catalysts is herewith described. New catalysts 1-3 were applied in asymmetric transformations, such as the FriedelCrafts alkylation of indole, as well as in the transfer hydrogenation of nitroo
- Schneider, Jakob F.,Falk, Florian C.,Froehlich, Roland,Paradies, Jan
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supporting information; experimental part
p. 2265 - 2269
(2010/07/10)
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- Transfer hydrogenation in water: Enantioselective, catalytic reduction of (E)-β,β-disubstituted nitroalkenes
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A mild catalytic asymmetric transfer hydrogenation of β,β- disubstituted nitroalkenes Is reported. Formic acid Is used as a reductant in combination with an Ir catalyst. The reaction Is conducted in water at low pH and open to air to give adducts In prepa
- Soltani, Omid,Ariger, Martin A.,Carreira, Erick M.
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supporting information; experimental part
p. 4196 - 4198
(2009/12/31)
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- Sugar-based phosphite and phosphoroamidite ligands for the Cu-catalyzed asymmetric 1,4-addition to enones
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A modular sugar-based phosphoroamidite L1-L5a-g and phosphite L6-L9a-g ligand library was tested in the asymmetric Cu-catalyzed 1,4-conjugate addition reactions of β-substituted (cyclic and linear) and β,β′-disubstituted (cyclic) enones. The selectivity d
- Raluy, Eva,Pamies, Oscar,Dieguez, Montserrat,Rosset, Stephane,Alexakis, Alexander
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experimental part
p. 2167 - 2172
(2010/03/24)
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- Asymmetric bioreduction of C=C bonds using enoate reductases OPR1, OPR3 and YqjM: Enzyme-based stereocontrol
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Three cloned enoate reductases from the "old yellow enzyme" family of flavoproteins were investigated in the asymmetric bioreduction of activated alkenes. 12-Oxophytodienoate reductase isoenzymes OPR1 and OPR3 from Lycopersicon esculentum (tomato), and YqjM from Bacillus subtilis displayed a remarkably broad substrate spectrum by reducing α,β-unsaturated aldehydes, ketones, maleimides and nitroalkenes. The reaction proceeded with absolute chemoselectivity-only the conjugated C=C bond was reduced, while isolated olefins and carbonyl groups remained intact-with excellent stereoselectivities (ees up to >99%). Upon reduction of a nitroalkene, the stereochemical outcome could be determined via choice of the appropriate enzyme (OPR1 versus OPR3 or YqjM), which furnished the corresponding enantiomeric nitroalkanes in excellent ee. Molecular modelling suggests that this "enzyme-based stereocontrol" is caused by subtle differences within the active site geometries.
- Hall, Melanie,Stueckler, Clemens,Ehammer, Heidemarie,Pointner, Eva,Oberdorfer, Gustav,Gruber, Karl,Hauer, Bernard,Stuermer, Rainer,Kroutil, Wolfgang,Macheroux, Peter,Faber, Kurt
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experimental part
p. 411 - 418
(2009/04/10)
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- Structure-based insight into the asymmetric bioreduction of the C=C double bond of α,β-unsaturated nitroalkenes by pentaerythritol tetranitrate reductase
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Biocatalytic reduction of α- or β-alkyl-barylnitroalkenes provides a convenient and efficient method to prepare chiral substituted nitroalkanes. Pentaerythritol tetranitrate reductase (PETN reductase) from Enterobacter cloacae st. PB2 catalyses the reduction of nitroolefins such as 1-nitrocyclohexene (1) with steady state and rapid reaction kinetics comparable to other old yellow enzyme homologues. Furthermore, it reduces 2-aryl-1-nitropropenes (4a-d) to their equivalent (S)-nitropropanes 9a-d. The enzyme shows a preference for the (Z)-isomer of substrates 4a-d, providing almost pure enantiomeric products 9a-d (ees up to > 99%) in quantitative yield, whereas the respective (E)-isomers are reduced with lower enantioselectivity (63-89% ee) and lower product yields. 1-Aryl-2-nitropropenes (5a, b) are also reduced efficiently, but the products (R)-10 have lower optical purities. The structure of the enzyme complex with 1-nitrocyclohexene (1) was determined by X-ray crystallography, revealing two substrate-binding modes, with only one compatible with hydride transfer. Models of nitropropenes 4 and 5 in the active site of PETN reductase predicted that the enantioselectivity of the reaction was dependent on the orientation of binding of the (E)- and (Z)- substrates. This work provides a structural basis for understanding the mechanism of asymmetric bioreduction of nitroalkenes by PETN reductase.
- Toogood, Helen S.,Fryszkowska, Anna,Hare, Victoria,Fisher, Karl,Roujeinikova, Anna,Leys, David,Gardiner, John M.,Stephens, Gill M.,Scrutton, Nigel S.
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supporting information; experimental part
p. 2789 - 2803
(2009/10/20)
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- Highly enantioselective reduction of β,β-disubstituted aromatic nitroalkenes catalyzed by Clostridium sporogenes
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(Chemical Equation Presented) This is the first report of the use of Clostridium sporogenes extracts for enantioselective reduction of C=C double bonds of β,β-disubstituted (1) and α,β-disubstituted nitroalkenes (3). Crude enzyme preparations reduced aryl derivatives 1a-e and 1h, in 35-86% yield with ≥97% ee. Reduction of (E)- and (Z)-isomers of 1c gave the same enantiomer of 2c (≥99% ee). In contrast, α,β- disubstituted nitroalkene 3a was a poor substrate, yielding (S)-4a in low yield (10-20%), and the ee (30-70% ee) depended on NADH concentration. An efficient synthesis of a library of nitroalkenes 1 is described.
- Fryszkowska, Anna,Fisher, Karl,Gardiner, John M.,Stephens, Gill M.
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p. 4295 - 4298
(2008/12/20)
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- Optically active nitrile oxides: synthesis and 1,3-dipolar cycloaddition reactions
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Baker's yeast-promoted reduction of the C{double bond, long}C bond in 2-aryl-1-nitropropenes gave the corresponding optically active (R)-2-aryl-1-nitropropanes of high enantiomeric purity (ee >90%). They were next converted with the aid of the Mukaiyama and Hoshino method into the optically active nitrile oxides, which were made to react in situ with ethyl propiolate, methylvinyl ketone and (R)-1-phenyl-2-(phenylsulfonyl)ethyl acrylate to yield the appropriate, enantiomerically enriched, isoxazoles or 4,5-dihydroisoxazoles as diastereomeric mixtures, respectively.
- Zagozda, Marcin,Plenkiewicz, Jan
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p. 1457 - 1464
(2008/02/11)
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- Organocatalytic asymmetric transfer hydrogenation of nitroolefins
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We describe a highly efficient and highly enantioselective Hantzsch ester mediated conjugate transfer hydrogenation of β,β-disubstituted nitroolefins that is catalyzed by a Jacobsen-type thiourea catalyst. Copyright
- Martin, Nolwenn J. A.,Ozores, Lidia,List, Benjamin
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p. 8976 - 8977
(2008/02/10)
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- Asymmetric bioreduction of activated alkenes using cloned 12-oxophytodienoate reductase isoenzymes OPR-1 and OPR-3 from Lycopersicon esculentum (tomato): A striking change of stereoselectivity
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(Chemical Equation Presented) Tomato source: 12-Oxophytodienoate reductase isoenzymes OPR1 and OPR3 from tomato possess a broad substrate spectrum for the asymmetric bioreduction of α,β-unsaturated enals, enones, dicarboxylic acids, and N-substituted male-imides (see scheme). Stereocomplementary behavior of both isoenzymes was observed in the reduction of a nitroalkene that led to the formation of opposite stereoisomers in high enantiomeric excess.
- Hall, Melanie,Stueckler, Clemens,Kroutil, Wolfgang,Macheroux, Peter,Faber, Kurt
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p. 3934 - 3937
(2008/03/11)
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- Cu-catalysed asymmetric 1,4-addition of Me3Al to nitroalkenes. Synthesis of (+)-ibuprofen
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Trimethylaluminium undergoes enantioselective (ee up to 93%) copper-catalysed Michael addition to various nitroalkenes. Copper thiophenecarboxylate (CuTC) (2 mol %) and 4 mol % of a chiral phosphoramidite ligand are sufficient for a complete and clean reaction. The synthesis of (+)-ibuprofen is described with 82% ee.
- Polet, Damien,Alexakis, Alexandre
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p. 1529 - 1532
(2007/10/03)
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- METHOD FOR PRODUCING AN OPTICALLY ACTIVE NITRO COMPOUND
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An optically active nitro compound having two hydrogen atoms on its α-cabon atom and having β-asymmetric carbon atom can be produced by making α, β-unsaturated nitroolefin having a hydrogen atom on its α-cabon atom react with at least two organosilicon compounds having at lest one silicon-hydrogen bond in the molecule in the presence of an asymmetric copper complex, or react with an organosilicon compound having at least one silicon-hydrogen bond in the molecule in the presence of an asymmetric copper complex and water.
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- Palladium-catalyzed conjugate addition of organosiloxanes to α,β-unsaturated carbonyl compounds and nitroalkenes
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The addition of aryltrialkoxysilanes to α,β-unsaturated carbonyl compounds (ketones, aldehydes) and nitroalkenes in the presence of SbCl3, TBAF, AcOH, and a catalytic amount of Pd(OAc)2, in CH3CN at 60 °C, provides the corresponding conjugate addition products in moderate to good yields. The addition of equimolar amounts of SbCl3 and TBAF is necessary for this reaction to proceed smoothly. The arylpalladium complex, which is generated by the transmetalation from a putative hypercoordinate silicon compound, is considered to be the catalytically active species.
- Denmark, Scott E.,Amishiro, Nobuyoshi
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p. 6997 - 7003
(2007/10/03)
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- Generation of nitroalkanes, hydroximoyl halides and nitrile oxides from the reactions of β-nitrostyrenes with Grignard or organolithium reagents
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The β-nitrostyrenes 1 or 2 react with Grignard or organolithium reagents in ether or THF solution to generate by 1,4-addition the intermediate nitronates A. When A is treated with dilute hydrochloric acid, high yields of the nitroalkanes 3 (and oximes 4) or 5 are obtained Hydroximoyl halides 6, 8 or nitrile oxides 7 can be isolated when the intermediate A is slowly added to the ice cold concentrated hydrohalic acid. The same products 6 and/or 7 are observed if the nitronates, generated from the substrate 1a, are added to 85% aqueous H2SO4 but only the hydrolyzed carboxylic acids 9 are generated when the β-nitrostyrenes 2 are reacted with Grignard reagents and worked up under the same condition. The nitrile oxides 7 can undergo 1,3-dipolar cycloaddition with alkenes or alkynes to generate 2-isoxazolines or isoxazoles. A one-pot synthesis of the [n,3,0] bicyclic (n = 3 or 4) compounds 23-27 by intramolecular nitrile oxide-olefin cycloadditions is reported.
- Yao, Ching-Fa,Kao, Kuo-Hsi,Liu, Ju-Tsung,Chu, Cheng-Ming,Wang, Yeh,Chen, Wen-Chang,Lin, Yu-Mei,Lin, Wen-Wei,Yan, Ming-Chung,Liu, Jing-Yuan,Chuang, Ming-Ching,Shiue, Jin-Lien
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p. 791 - 822
(2007/10/03)
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- Additions of organomanganese reagents to conjugated nitroolefins
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Additions of organomanganese reagents to aromatic and aliphatic conjugated nitroolefins were examined for the first time. In most cases reaction proceeded rapidly at -30°C. Unlike Mn reagents lacking β-hydrogens (Me, Ph), which lead to oxidative coupling and reductive dimerisation of nitrostyrenes, benzylmanganese chloride gives 1,4-addition in yields exceeding Grignard or Cu-assisted additions. At 0°C alkyl(Bu, Pr)-manganese reagents undergo an addition-migration-elimination process with nitrostyrenes providing a convenient and stereospecific entry into arylated trans-olefins.
- Namboothiri,Hassner, Alfred
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- Potential GABAB Receptor Antagonists. VII. The Synthesis of 2-(4-Chlorophenyl)-3-nitropropan-1-amine and Related Analogues of Baclofen
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3-Nitro-2-phenylpropan-1-amine and 2-(4-chlorophenyl)-3-nitropropan-1-amine have been synthesized by the addition of nitrous acid to the corresponding trifluoroacetylaminomethylstyrenes followed by reduction of the double bond with sodium borohydride.A more general and efficient route involves the Michael addition of nitroalkane anions to methyl cinnamates followed by Curtius degradation of the corresponding acids. 2-(4-Chlorophenyl)-3-nitropropan-1-amine is a specific agonist of GABA and the GABAB receptor, with about half the activity of racemic baclofen at the isolated guinea pig ileum.Methylation or dimethylation at C3 decreases activity markedly.
- Abbenante, Giovanni,Hughes, Robert,Prager, Rolf H.
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p. 1441 - 1452
(2007/10/02)
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- Asymmetric Reduction of Nitro Olefins by Fermenting Bakers' Yeast
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Reduction of a number of 1-nitro-1-alkenes by fermenting bakers' yeast has been found to be enantioselective, resulting in the formation of optically active 1-nitroalkanes.In most cases, optical purities of the products determined by HPLC analysis of MTPA amides were as high as 83-98percent ee.The optimum rate of conversion was obtained when the reaction was carried out at pH 8 and low concentration of substrates.The absolute configuration of resulting (+)-1-nitro-2-phenylpropane was determined to be R by comparing the specific rotation with that of an authentic specimen after reductive hydrolysis to the corresponding aldehyde.
- Ohta, Hiromichi,Kobayashi, Naoki,Ozaki, Kazuhiko
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p. 1802 - 1804
(2007/10/02)
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- Asymmetric Hydrogenation of 2-Aryl-1-nitropropenes by Fermenting Bakers'Yeast
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2-Aryl-1-nitropropenes were enantioselectively hydrogenated on C=C double bonds by incubation with fermenting bakers' yeast to afford optically active 2-aryl-1-nitopropanes.
- Ohta, Hiromichi,Ozaki, Kazuhiko,Tsuchihashi, Gen-ichi
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p. 191 - 192
(2007/10/02)
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