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Dynamic Kinetic Resolution (dynamic + kinetic_resolution)
Selected AbstractsEnantioselective Synthesis of Chiral ,-Aryloxy Alcohols by Ruthenium-Catalyzed Ketone Hydrogenation via Dynamic Kinetic Resolution (DKR)ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Wen-Ju Bai Abstract A highly efficient enantioselective synthesis of chiral ,-aryloxy alcohols by the {RuCl2[(S)-SDP][(R,R)-DPEN]} [(Sa,R,R)- 1a; SDP=7,7,-bis(diarylphosphino)-1,1,-spirobiindane; DPEN=trans -1,2-diphenylethylenediamine] complex-catalyzed asymmetric hydrogenation of racemic ,-aryloxydialkyl ketones via dynamic kinetic resolution (DKR) has been developed. Enantioselectivities of up to 99% ee with good to high cis/anti -selectivities (up to>99:1) were achieved. [source] Enantioselective Synthesis of Chiral ,-Aryloxy Alcohols by Asymmetric Hydrogenation of ,-Aryloxy Aldehydes via Dynamic Kinetic ResolutionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Zhang-Tao Zhou Abstract A catalytic enantioselective hydrogenation of racemic ,-aryloxy aldehydes via dynamic kinetic resolution has been developed by using (diamine)(spirodiphosphine)ruthenium(II) chloride [RuCl2(SDPs)(diamine)] catalysts. Employing this new reaction system a variety of optically active ,-aryloxy primary alcohols were synthesized in high yields and moderate to good enantioselectivities. [source] Stereoselective Synthesis of Three Isomers of tert -Butyl 5-Hydroxy-4-methyl-3-oxohexanoate through Alcohol Dehydrogenase-Catalyzed Dynamic Kinetic ResolutionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Steffen Lüdeke Abstract Regioselective reduction of the 5-keto group of tert -butyl 4-methyl-3,5-dioxohexanoate (1) leads to a stereodiad of tert -butyl 5-hydroxy-4-methyl-3-oxohexanoate (2). Alcohol dehydrogenases from Lactobacillus brevis (LBADH), Rhodococcus sp. (RS 1-ADH) and Saccharomyces cerevisiae (YGL157w) reduce 1 under dynamic kinetic resolution conditions, thereby establishing two chiral carbons with a single reduction step. While it had been shown previously that LBADH reduction of 1 stereoselectively leads to syn -(4S,5R)- 2, alcohol dehydrogenase-mediated dynamic kinetic resolution now allows easy access to syn -(4R,5S)- 2 (RS 1-ADH; 97.6% ee, syn:anti=92:8, 66% conversion, 37% isolated yield) and anti -(4S,5S)- 2 (YGL157w; 90% ee, anti:syn=93:7, 64% conversion, 42% isolated yield), as well. Thus three out of four possible stereoisomers were formed selectively upon reduction of 1. [source] ChemInform Abstract: Highly Efficient Dynamic Kinetic Resolution of Secondary Aromatic Alcohols with Low-Cost and Easily Available Acid Resins as Racemization Catalysts.CHEMINFORM, Issue 32 2010Yongmei Cheng Abstract A combination of Novozym435 with an acidic polystyrene resin CD8604 affords a new and efficient dynamic kinetic resolution of acetophenones to give the corresponding benzylic alcohols with good to excellent enantioselectivities. [source] ChemInform Abstract: Dynamic Kinetic Resolution: Asymmetric Transfer Hydrogenation of ,-Alkyl-Substituted ,-Ketoamides.CHEMINFORM, Issue 26 2010John Limanto Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Direct Asymmetric Dynamic Kinetic Resolution by Combined Lipase Catalysis and Nitroaldol (Henry) Reaction.CHEMINFORM, Issue 27 2008Pornrapee Vongvilai Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Dynamic Kinetic Resolution of Hemiaminals Using a Novel DMAP Catalyst.CHEMINFORM, Issue 15 2008Shinji Yamada Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Chemoenzymatic Dynamic Kinetic Resolution of Allylic Alcohols: A Highly Enantioselective Route to Acyloin Acetates.CHEMINFORM, Issue 52 2007Krisztian Bogar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] High-Yielding Metalloenzymatic Dynamic Kinetic Resolution of Fluorinated Aryl Alcohols.CHEMINFORM, Issue 46 2007Krisztian Bogar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Enantio- and Diastereoselective Hydrogenation via Dynamic Kinetic Resolution by a Cationic Iridium Complex in the Synthesis of ,-Hydroxy-,-amino Acid Esters.CHEMINFORM, Issue 3 2007Kazuishi Makino Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Enantioselective Synthesis of Vicinal Halohydrins via Dynamic Kinetic Resolution.CHEMINFORM, Issue 20 2006Abel Ros Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] (S)-Selective Kinetic Resolution and Chemoenzymatic Dynamic Kinetic Resolution of Secondary Alcohols.CHEMINFORM, Issue 16 2006Linnea Boren Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Palladium-Catalyzed Asymmetric Synthesis of Allylic Alcohols from Unsymmetrical and Symmetrical Racemic Allylic Carbonates Featuring C,O Bond Formation and Dynamic Kinetic Resolution.CHEMINFORM, Issue 51 2005Hans-Joachim Gais Abstract For Abstract see ChemInform Abstract in Full Text. [source] Dynamic Kinetic Resolution of ,-Bromo Carboxylic Acid Derivatives in Asymmetric Nucleophilic Substitution with Chiral ,-Amino Esters.CHEMINFORM, Issue 47 2005Ji-yeon Chang Abstract For Abstract see ChemInform Abstract in Full Text. [source] Removal of the Acyl Donor Residue Allows the Use of Simple Alkyl Esters as Acyl Donors for the Dynamic Kinetic Resolution of Secondary Alcohols.CHEMINFORM, Issue 38 2005Gerard K. M. Verzijl Abstract For Abstract see ChemInform Abstract in Full Text. [source] Chemoenzymatic Dynamic Kinetic Resolution of ,-Halo Alcohols.CHEMINFORM, Issue 17 2003An Efficient Route to Chiral Epoxides. Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Enzymatic Kinetic Resolution and Chemoenzymatic Dynamic Kinetic Resolution of ,-Hydroxy Esters.CHEMINFORM, Issue 29 2002-Lactones., An Efficient Route to Chiral Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Dynamic Kinetic Resolution of tert-Butyl 4-Methyl-3,5-dioxohexanoate Through Enzymatic Reduction.CHEMINFORM, Issue 16 2001Aiguo Ji Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of PiperidinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2006Mercedes Amat Prof. Abstract A straightforward procedure for the synthesis of enantiopure polysubstituted piperidines is reported. It involves the direct generation of chiral non-racemic oxazolo[3,2- a]piperidone lactams that already incorporate carbon substituents on the heterocyclic ring and the subsequent removal of the chiral auxiliary. The key step is a cyclocondensation reaction of (R)-phenylglycinol or other amino alcohols with racemic or prochiral ,-oxo (di)acid derivatives in highly stereoselective processes involving dynamic kinetic resolution and/or desymmetrization of diastereotopic or enantiotopic ester groups. Se describe un procedimiento directo para la síntesis enantioselectiva de piperidinas polisustituidas. Consiste en la generación directa de oxazolo[3,2-a]piperidonas quirales no racémicas que ya incorporan sustituyentes carbonados en las diferentes posiciones del heterociclo, y en la posterior eliminación del auxiliar quiral. La etapa clave es una reacción de ciclocondensación entre el (R)-fenilglicinol, u otros amino alcoholes quirales, con derivados de , -oxo ácidos racémicos o proquirales, en procesos altamente estereoselectivos que implican una resolución cinética dinámica y/o la desimetrización de grupos diastereotópicos o enantiotópicos. [source] Dynamic Enzymatic Kinetic Resolution of Methyl 2,3-Dihydro-1H -indene-1-carboxylateEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2009Jörg Pietruszka Abstract A new reaction setup for kinetic enzymatic resolution was established and is demonstrated for the case of the hydrolase-catalysed conversion of methyl 2,3-dihydro-1H -indene-1-carboxylate (1) in conjunction with a base-catalysed racemisation. The system allows controlled racemisation, resulting in efficient dynamic kinetic resolution (DKR) of the title compound. Short reaction times and high enantioselectivities were obtained with CAL-B and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene). Compound (R)- 1 (ee 95,%) served as a starting material in a domino reaction that led to the biaryl indanyl ketone (R)- 8, a lead compound for novel inhibitors of peptidyl-prolyl- cis/trans -isomerases, in 94,% ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Enantioselective Synthesis of Chiral ,-Aryloxy Alcohols by Ruthenium-Catalyzed Ketone Hydrogenation via Dynamic Kinetic Resolution (DKR)ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Wen-Ju Bai Abstract A highly efficient enantioselective synthesis of chiral ,-aryloxy alcohols by the {RuCl2[(S)-SDP][(R,R)-DPEN]} [(Sa,R,R)- 1a; SDP=7,7,-bis(diarylphosphino)-1,1,-spirobiindane; DPEN=trans -1,2-diphenylethylenediamine] complex-catalyzed asymmetric hydrogenation of racemic ,-aryloxydialkyl ketones via dynamic kinetic resolution (DKR) has been developed. Enantioselectivities of up to 99% ee with good to high cis/anti -selectivities (up to>99:1) were achieved. [source] Enantioselective Synthesis of Chiral ,-Aryloxy Alcohols by Asymmetric Hydrogenation of ,-Aryloxy Aldehydes via Dynamic Kinetic ResolutionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Zhang-Tao Zhou Abstract A catalytic enantioselective hydrogenation of racemic ,-aryloxy aldehydes via dynamic kinetic resolution has been developed by using (diamine)(spirodiphosphine)ruthenium(II) chloride [RuCl2(SDPs)(diamine)] catalysts. Employing this new reaction system a variety of optically active ,-aryloxy primary alcohols were synthesized in high yields and moderate to good enantioselectivities. [source] Stereoselective Synthesis of Three Isomers of tert -Butyl 5-Hydroxy-4-methyl-3-oxohexanoate through Alcohol Dehydrogenase-Catalyzed Dynamic Kinetic ResolutionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Steffen Lüdeke Abstract Regioselective reduction of the 5-keto group of tert -butyl 4-methyl-3,5-dioxohexanoate (1) leads to a stereodiad of tert -butyl 5-hydroxy-4-methyl-3-oxohexanoate (2). Alcohol dehydrogenases from Lactobacillus brevis (LBADH), Rhodococcus sp. (RS 1-ADH) and Saccharomyces cerevisiae (YGL157w) reduce 1 under dynamic kinetic resolution conditions, thereby establishing two chiral carbons with a single reduction step. While it had been shown previously that LBADH reduction of 1 stereoselectively leads to syn -(4S,5R)- 2, alcohol dehydrogenase-mediated dynamic kinetic resolution now allows easy access to syn -(4R,5S)- 2 (RS 1-ADH; 97.6% ee, syn:anti=92:8, 66% conversion, 37% isolated yield) and anti -(4S,5S)- 2 (YGL157w; 90% ee, anti:syn=93:7, 64% conversion, 42% isolated yield), as well. Thus three out of four possible stereoisomers were formed selectively upon reduction of 1. [source] Enzyme-assisted physicochemical enantioseparation processes,Part III: Overcoming yield limitations by dynamic kinetic resolution of asparagine via preferential crystallization and enzymatic racemizationBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009Kerstin Würges Abstract The application of enantioseparation methods alone can only yield up to 50% of the desired chiral product. Thus enantioseparation becomes more attractive when accompanied by the racemization of the counter-enantiomer. Here we present first results of dynamic kinetic resolution of L -asparagine (L -Asn) via preferential crystallization and enzymatic racemization from a racemic, supersaturated solution on a 20,mL scale. An enzyme lyophilisate (WT amino acid racemase from P. putida KT2440 (E.C. 5.1.1.10), overexpressed in E. coli BL21(DE3)) was used for in situ racemization (enzyme concentrations varying from 0 to 1,mg/mL). When preferential crystallization was applied without any enzyme, a total of 31,mg of L -Asn monohydrate could be crystallized, before crystal formation of d -Asn started. Crystallization experiments accompanied by enzymatic racemization led to a significant increase of crystallized L -Asn (198,mg L -Asn monohydrate; >92%ee) giving the first experimental proof for this new process concept of dynamic kinetic resolution via preferential crystallization and enzymatic racemization. Measurements of the racemase activity before and after the crystallization process showed no significant differences, which would allow for enzyme recovery and recycling. Biotechnol. Bioeng. 2009; 104: 1235,1239. © 2009 Wiley Periodicals, Inc. [source] Model-based characterization of an amino acid racemase from Pseudomonas putida DSM 3263 for application in medium-constrained continuous processesBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2007M. Bechtold Abstract The amino acid racemase with broad substrate specificity from Pseudomonas putida DSM 3263 was overproduced and characterized with respect to application in an integrated multi-step process (e.g., dynamic kinetic resolution) that,theoretically,would allow for 100% chemical yield and 100% enantiomeric excess. Overexpression of the racemase gene in Escherichia coli delivered cell free extract with easily sufficient activity (20,50 U,mg,1 total protein) for application in an enzyme membrane reactor (EMR) setting. Model-based experimental analysis of a set of enzyme assays clearly indicated that racemization of the model substrates D - or L -methionine could be accurately described by reversible Michaelis,Menten kinetics. The corresponding kinetic parameters were determined from progress curves for the entire suitable set of aqueous-organic mixtures (up to 60% methanol and 40% acetonitrile) that are eligible for an integrated process scheme. The resulting kinetic expression could be successfully applied to describe enzyme membrane reactor performance under a large variety of settings. Model-based calculations suggested that a methanol content of 10% and an acetonitrile content of 20% provide maximum productivity in EMR operations. However product concentrations were decreased in comparison to purely aqueous operation due to decreasing solubility of methionine with increasing organic solvent content. Finally, biocatalyst stability was investigated in different solvent compositions following a model-based approach. Buffer without organic content provided excellent stability at moderate temperatures (20,35°C) while addition of 20% acetonitrile or methanol drastically reduced the half-life of the racemase. Biotechnol. Bioeng. 2007; 98: 812,824. © 2007 Wiley Periodicals, Inc. [source] ChemInform Abstract: Highly Efficient Dynamic Kinetic Resolution of Secondary Aromatic Alcohols with Low-Cost and Easily Available Acid Resins as Racemization Catalysts.CHEMINFORM, Issue 32 2010Yongmei Cheng Abstract A combination of Novozym435 with an acidic polystyrene resin CD8604 affords a new and efficient dynamic kinetic resolution of acetophenones to give the corresponding benzylic alcohols with good to excellent enantioselectivities. [source] Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of PiperidinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2006Mercedes Amat Prof. Abstract A straightforward procedure for the synthesis of enantiopure polysubstituted piperidines is reported. It involves the direct generation of chiral non-racemic oxazolo[3,2- a]piperidone lactams that already incorporate carbon substituents on the heterocyclic ring and the subsequent removal of the chiral auxiliary. The key step is a cyclocondensation reaction of (R)-phenylglycinol or other amino alcohols with racemic or prochiral ,-oxo (di)acid derivatives in highly stereoselective processes involving dynamic kinetic resolution and/or desymmetrization of diastereotopic or enantiotopic ester groups. Se describe un procedimiento directo para la síntesis enantioselectiva de piperidinas polisustituidas. Consiste en la generación directa de oxazolo[3,2-a]piperidonas quirales no racémicas que ya incorporan sustituyentes carbonados en las diferentes posiciones del heterociclo, y en la posterior eliminación del auxiliar quiral. La etapa clave es una reacción de ciclocondensación entre el (R)-fenilglicinol, u otros amino alcoholes quirales, con derivados de , -oxo ácidos racémicos o proquirales, en procesos altamente estereoselectivos que implican una resolución cinética dinámica y/o la desimetrización de grupos diastereotópicos o enantiotópicos. [source] | ||||||||||