- Effect of organic solvents on asymmetric reduction of β-keto esters using cyanobacterium Synechocystis sp. PCC 6803
-
The asymmetric reduction of tert-butyl 3-oxobutanoate by cyanobacterium Synechocystis sp. PCC 6803 under illumination with red LED light at 25 °C for 24 h afforded the corresponding (R)-β-hydroxy ester in 79% enantiomeric excess (ee) (81% yield), while the addition of toluene (1% (v/v)) to the system gave the corresponding (S)-β-hydroxy ester in >99% ee (87% yield). Organic solvents such as chloroform, benzene, ethylbenzene, cyclohexane, and methylcyclohexane showed similar effects and afforded the corresponding (S)-β-hydroxy ester in >99% ee. However, polar organic solvents, such as DMSO, THF, and ethanol, as well as dodecane—a hydrophobic solvent with a straight long-chain—did not exhibit such effects.
- Tanaka, Shusei,Kojima, Hideo,Takeda, Satomi,Yamanaka, Rio,Takemura, Tetsuo
-
supporting information
(2021/07/25)
-
- Asymmetric visible-light photobiocatalytic reduction of β-keto esters utilizing the cofactor recycling system in Synechocystis sp. PCC 6803
-
The asymmetric reduction of β-keto esters employing a wild-type strain of cyanobacterium Synechocystis sp. PCC 6803 under illumination of red LED light at 25 °C for 24 h was evaluated. As a result, the corresponding (R)-β-hydroxy esters were obtained as major products. The R-selectivity was shown to increase for bulkier substrates. Moreover, it was also found that the R-selectivity increased with decreasing substrate concentrations. This can be explained by the assumption that the Km value of the R-selective reductase is smaller than that of the S-selective enzyme involved in the reaction. Additionally, it was demonstrated that the R-selective reductase required the light-dependent production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) for effective reaction; however, the S-selective variant did not. Overall, cyanobacterium was employed as a sustainable photobiocatalyst proliferating under illumination of light, while utilizing inorganic salts and atmospheric carbon dioxide (CO2). Employing the whole-cell system allowed for the preparation of industrially-important chiral compounds, such as optically active β-hydroxy esters.
- Tanaka, Shusei,Kojima, Hideo,Takeda, Satomi,Yamanaka, Rio,Takemura, Tetsuo
-
supporting information
(2020/05/08)
-
- Chiral BINAP-based hierarchical porous polymers as platforms for efficient heterogeneous asymmetric catalysis
-
Two vinyl-functionalized chiral 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) ligands, (S)-4,4′-divinyl-BINAP and (S)-5,5′-divinyl-BINAP, were successfully synthesized. Chiral BINAP-based porous organic polymers (POPs), denoted as 4-BINAP@POPs and 5-BINAP@POPs, were efficiently prepared via the copolymerization of vinyl-functionalized BINAP with divinyl benzene under solvothermal conditions. Thorough characterization using nuclear magnetic resonance spectroscopy, thermogravimetric analysis, extended X-ray absorption fine structure analysis, and high-angle annular dark-field scanning transmission electron microscopy, we confirmed that chiral BINAP groups were successfully incorporated into the structure of the materials considered to contain hierarchical pores. Ru was introduced as a catalytic species into the POPs using different synthetic routes. Systematic investigation of the resultant chiral Ru/POP catalysts for heterogeneous asymmetric hydrogenation of β-keto esters revealed their excellent chiral inducibility as well as high activity and stability. Our work thereby paves a path towards the use of advanced hierarchical porous polymers as solid chiral platforms for heterogeneous asymmetric catalysis.
- Wang, Tao,Lyu, Yuan,Xiong, Kai,Wang, Wenlong,Zhang, Hao,Zhan, Zhuangping,Jiang, Zheng,Ding, Yunjie
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p. 890 - 897
(2017/05/22)
-
- Ru coordinated with BINAP in knitting aryl network polymers for heterogeneous asymmetric hydrogenation of methyl acetoacetate
-
A facile method for the preparation of heterogeneous asymmetric hydrogenation catalysts was presented. BINAP was knitted with aryl compounds using formaldehyde dimethyl acetal (FDA) as a cross-linker by Friedel-Crafts reaction without any pre-modification. The prepared catalysts showed different catalytic activities, and excellent recyclablilty results could be achieved in asymmetric hydrogenation.
- Wang, Tao,Lyu, Yuan,Chen, Xingkun,Li, Cunyao,Jiang, Miao,Song, Xiangen,Ding, Yunjie
-
p. 28447 - 28450
(2016/04/08)
-
- Laboratory scale-up synthesis of chiral carbinols using Rhizopus arrhizus
-
Rhizopus arrhizus mediated bioreduction was optimized using acetophenone as a model substrate. Various parameters such as bio-processing conditions, reaction time, substrate concentration, temperature, and solvent carrier were studied. This optimized protocol was further exploited for scaled up bioreductions of various prochiral ketones. This study demonstrates the versatility of the fungus Rhizopus arrhizus as a biocatalyst to obtain chiral carbinols in good to excellent yields and selectivities.
- Salvi, Neeta A.,Chattopadhyay, Subrata
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p. 188 - 192
(2018/10/09)
-
- Improving the toolbox of bioreductions by the use of continuous flow systems
-
Packed bed reactors can be used as an interesting alternative on the bioreduction of β-ketoesteres mediated by immobilized microorganisms. Here in, we report our results on the bioreduction of ethyl 3-oxohexanoate by immobilized Kluyveromyces marxianus cells and tert-butyl 3-oxobutanoate by immobilized Rhodotorula rubra cells under continuous flow conditions leading the desired β-hydroxy esters corresponding in high yields and enantiomeric excess.
- Lopes, Raquel O.,Grimm, Simon,Ribeiro, Joyce B.,Leal, Ivana C. R.,Miranda, Leandro S. M.,De Souzae, Rodrigo O. M. A.
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p. 550 - 554
(2015/04/27)
-
- General Stereodivergent Enantioselective Total Synthetic Approach toward Macrosphelides A-G and M
-
A straightforward enantioselective total synthesis algorithm for the preparation of 8 out of 13 macrosphelides within 9-11 steps starting from tert-butyl sorbate is presented. The use of a cyclic sulfate as both protecting and reactivity directing group is the key element within this algorithm. A high-pressure transesterification allows for the selective ring-enlargement of the 15-membered macrosphelides into the 16-membered counterparts. The absolute configurations of the natural products were unambiguously assigned both by the chemical synthesis and by X-ray structure analysis.
- H?cker, Christine,Plietker, Bernd
-
p. 8055 - 8064
(2015/09/02)
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- Enhanced enantioselectivity in the heterogeneous catalytic hydrogenation of acetoacetate esters into the corresponding 3-hydroxybutyrates using commercial nickel powder
-
Heterogeneous catalytic hydrogenation of acetoacetic acid esters over tartaric acid/NaBr-modified Ni powder was determined to be a critical function of the steric bulk of the ester moiety to afford quantitatively 3-hydroxybutyrate in 94% enantiomeric excess when ethyl and i-butyl esters are used, providing a facile route to optically active 3-hydroxybutyrates.
- Osawa, Tsutomu,Kizawa, Tomoko,Ikeda, Shinji,Kitamura, Takayuki,Inoue, Yoshihisa,Borovkov, Victor
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p. 1630 - 1633
(2015/01/09)
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- Whole cells in enantioselective reduction of tert-butyl acetoacetate
-
The b-ketoester tert-butyl acetoacetate was enantioselectively reduced to tertbutyl (S)-3-hydroxybutanoate by seven microorganism strains. The best result using free cells was obtained with the yeast R. rubra, which furnished 97.6% ee and higher than 99% of conversion within 24 h. After immobilization in calcium alginate spheres, R. rubra furnished 96% ee and higher than 99% ee within 24 h, even if substrate concentration was 58mM. Immobilized cells were reused three times without loss of enantioselectivity. Copyright Taylor & Francis Group, LLC.
- De Souza Ramos, Aline,Ribeiro, Joyce Benzaquem,De Oliveira Lopes, Raquel,De Souza, Rodrigo Octavio Mendonca Alves
-
p. 1611 - 1618
(2013/05/22)
-
- The effect of backbone stereochemistry on the folding of acyclic β2,3-aminoxy peptides
-
As a new type of foldamer, β-aminoxy peptides have the ability to adopt novel β N-O turns or β N-O helices in solution. Herein, we describe a new subclass of β-aminoxy peptide, that is, peptides of acyclic β2,3-aminoxy acids (NH2OCHR1CHR 2COOH), in which the presence of two chiral centers provides insight into the effect of backbone stereochemistry on the folding of β-aminoxy peptides. Acyclic β2,3aminoxy peptides with syn and anti configurations have been synthesized and their conformations investigated by NMR, IR, and circular dichroism (CD) spectroscopic, and X-ray crystallographic analysis. The ss N-O turns or β N-O helices, which feature ninemembered rings with intramolecular hydrogen bonds and have been identified previously in peptides of β3- and β2,2-aminoxy acids, are also predominantly present in the acyclic β2,3- aminoxy peptides with a syn configuration and N-O bonds gauche to the C a-Cβ bonds in both solution and the solid state. In the acyclic β2,3-aminoxy peptides with an anti configuration, an extended strand (i.e., non-hydrogenbonded state) is found in the solid state, and several conformations including non-hydrogen-bonded and intramolecular hydrogen-bonded states are present simultaneously in nonpolar solvents. These results suggest that the backbone stereochemistry does affect the folding of the acyclic β2,3-aminoxy peptides. Theoretical calculations on the conformations of model acyclic β2,3-aminoxy peptides with different backbone stereochemistry were also conducted to elucidate structural characteristics. Our present work may provide useful guidelines for the design and construction of new foldamers with predicable structures.
- Zhang, Yu-Hui,Song, Kesheng,Zhu, Nian-Yong,Yang, Dan
-
supporting information; experimental part
p. 577 - 587
(2010/06/12)
-
- A novel method for enzymatic asymmetric reduction of ketones in a supercritical carbon dioxide/water biphasic system
-
A novel method to enable asymmetric reduction of ketones by an alcohol dehydrogenase from Geotrichum candidum in a supercritical carbon dioxide and water biphasic system is described. The addition of sodium bicarbonate improved the reactivity up to a prac
- Harada, Tadao,Kubota, Yuki,Kamitanaka, Takashi,Nakamura, Kaoru,Matsuda, Tomoko
-
scheme or table
p. 4934 - 4936
(2009/12/01)
-
- Axial chirality control by 2,4-pentanediol for the alternative synthesis of c3-tunephos chiral diphosphine ligands and their applications in highly enantioselective ruthenium-catalyzed hydrogenation of β-keto esters
-
A highly efficient strategy for the synthesis of a series of C 3*-TunePhos chiral diphosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for the ruthenium-catalyzed asymmetric hydrogenation of β-keto esters. Up to 99% ee values were achieved for the enantioselective synthesis of β-hydroxy acid derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules.
- Sun, Xianfeng,Li, Wei,Hou, Guohua,Zhou, Le,Zhang, Xumu
-
supporting information; experimental part
p. 2553 - 2557
(2009/12/28)
-
- Effect of carbon dioxide concentrations on asymmetric reduction of ketones with plant-cultured cells
-
Enantioselectivities in asymmetric reduction of ketones were controlled by atmospheric carbon dioxide concentrations: the reaction in high carbon dioxide concentrations under illumination of fluorescent light afforded the corresponding l-alcohol while tha
- Kojima, Hideo,Okada, Akiko,Takeda, Satomi,Nakamura, Kaoru
-
experimental part
p. 7079 - 7081
(2010/03/01)
-
- Axially chiral P-N ligands for the copper catalyzed β-borylation of α,β-unsaturated esters
-
The synthesis and resolution of a new axially chiral Quinazolinap ligand are reported. The application of this and other related P-N ligands to the copper catalyzed β-borylation of α,β-unsaturated esters resulted in conversions of up to 100% and ee values
- Fleming, William J.,Mueller-Bunz, Helge,Lillo, Vanesa,Fernandez, Elena,Guiry, Patrick J.
-
supporting information; experimental part
p. 2520 - 2524
(2009/10/30)
-
- Asymmetric reduction of ketones by Geotrichum candidum: immobilization and application to reactions using supercritical carbon dioxide
-
The enantioselectivity for the reduction of ketones by Geotrichum candidum NBRC 5767 was improved upon immobilization of the whole cell onto an ion exchange resin with polyallylamine. Furthermore, immobilization of the cell enhanced the stability of the enzyme and enabled a continuous-flow reaction under normal aqueous conditions. The biocatalyst was also applied to the reaction in supercritical carbon dioxide.
- Matsuda, Tomoko,Marukado, Ryo,Mukouyama, Masaharu,Harada, Tadao,Nakamura, Kaoru
-
experimental part
p. 2272 - 2275
(2009/04/04)
-
- Asymmetric carbonyl reductions with microbial ketoreductases
-
The biocatalytic reduction of β-keto esters and some aromatic ketones in the presence of a variety of ketoreductases from different microbial origins was investigated. The prochiral selectivity was generally high and both product enantiomers could be obtained by a proper choice of enzyme. Aromatic ketones reacted slower than the esters but the prochiral selectivity was often high. The organic cosolvent tolerance of these enzymes was rather variable but useful activity could be maintained in a number of cases. Reduction of the oxidized cofactors NAD and NADP, employing 2-propanol as a sacrificial reductant, was catalyzed by the ketoreductases from Rhodococcus erythropolis and Lactobacillus kefir, respectively.
- Sorgedrager, Menno J.,Van Rantwijk, Fred,Huisman, Gjalt W.,Sheldon, Roger A.
-
scheme or table
p. 2322 - 2328
(2009/10/23)
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- An effective method to use ionic liquids as reaction media for asymmetric reduction by Geotrichum candidum
-
An effective method was developed to use an enzyme in ionic liquids; the asymmetric reduction of ketones by Geotrichum candidum in ionic liquids proceeded smoothly with excellent enantioselectivity when the cell was immobilized on water-absorbing polymer containing water, while the reaction without the polymer did not proceed.
- Matsuda, Tomoko,Yamagishi, Yusuke,Koguchi, Shinichi,Iwai, Noritaka,Kitazume, Tomoya
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p. 4619 - 4622
(2007/10/03)
-
- Thermomorphic system with non-fluorous phase-tagged Ru(BINAP) catalyst: Facile liquid/solid catalyst separation and application in asymmetric hydrogenation
-
The thermomorphic BINAP derivative 1 tagged with long alkyl chains was prepared from (S)-5,5′-diamino BINAP and applied to Ru-catalyzed asymmetric hydrogenation of β-ketoesters under homogeneous conditions in 3:1 (v/v) ethanol/ 1,4-dioxane at 60 °C with high enantioselectivity (up to 98% ee). Results indicated that the Ru(1) catalyst was easily recovered by simple cooling and precipitation and could be used for at least four cycles without any loss of enantioselectivity.
- Huang, Yi-Yong,He, Yan-Mei,Zhou, Hai-Feng,Wu, Lei,Li, Bao-Lin,Fan, Qing-Hua
-
p. 2874 - 2877
(2007/10/03)
-
- Polyethylene glycol as an environmentally friendly and recyclable reaction medium for enantioselective hydrogenation
-
Polyethylene glycol (PEG) was found to be an inexpensive, non-toxic and recyclable reaction medium for ruthenium- and rhodium-catalyzed asymmetric hydrogenation of 2-arylacrylic acids (Ru-catalyzed C=C bond reduction), enamides (Rh-catalyzed C=C bond reduction), β-keto esters and simple aromatic ketones (Ru-catalyzed C=O bond reduction). In all cases, high catalytic activities and enantioselectivities have been achieved, which are comparable to those obtained in conventional organic solvent systems. The Ru and Rh catalysts prepared with commercially available chiral diphosphine ligands could be readily recycled by simple extraction, as in the case of ionic liquids, and reused up to nine times without obvious loss of catalytic activity and enantioselectivity. The reduced products were obtained from the extracts in high isolated yields. These results indicate that PEGs as new reaction media are attractive alternatives to room temperature ionic liquids.
- Zhou, Hai-Feng,Fan, Qing-Hua,Tang, Wei-Jun,Xu, Li-Jin,He, Yan-Mei,Deng, Guo-Jun,Zhao, Li-Wen,Gu, Lian-Quan,Chan, Albert S. C.
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p. 2172 - 2182
(2007/10/03)
-
- Aminocyclopentadienyl Ruthenium Complexes as Racemization Catalysts for Dynamic Kinetic Resolution of Secondary Alcohols at Ambient Temperature
-
Aminocyclopentadienyl ruthenium complexes, which can be used as room-temperature racemization catalysts with lipases in the dynamic kinetic resolution (DKR) of secondary alcohols, were synthesized from cyclopenta-2,4-dienimines, Ru3(CO)12, and CHCl 3: [2,3,4,5-Ph4(η5-C 4CNHR)]Ru-(CO)2Cl (4: R = i-Pr; 5: R = n-Pr; 6: R = t-Bu), [2,5-Me2-3,4-Ph2(η5-C 4CNHR)]Ru(CO)2Cl (7: R = i-Pr; 8: R = Ph), and [2,3,4,5-Ph4(η5-C4CNHAr)]Ru(CO) 2Cl (9: Ar =p-NO2C6H4; 10: Ar = p-ClC6H4; 11: Ar = Ph; 12: Ar = p-OMeC6H 4; 13: Ar = p-NMe2C6H4). The tests in the racemization of (S)-4-phenyl-2-butanol showed that 7 is the most active catalyst, although the difference decreased in the DKR. Complex 4 was used in the DKR of various alcohols; at room temperature, not only simple alcohols but also functionalized ones such as allylic alcohols, alkynyl alcohols, diols, hydroxyl esters, and chlorohydrins were successfully transformed to chiral acetates. In mechanistic studies for the catalytic racemization, ruthenium hydride 14 appeared to be a key species. It was the major organometallic species in the racemization of (S)-1-phenylethanol with 4 and potassium tert-butoxide. In a separate experiment, (S)-1-phenylethanol was racemized catalytically by 14 in the presence of acetophenone.
- Choi, Jun Ho,Choi, Yoon Kyung,Kim, Yu Hwan,Park, Eun Sil,Kim, Eun Jung,Kim, Mahn-Joo,Park, Jaiwook
-
p. 1972 - 1977
(2007/10/03)
-
- Rhizopus arrhizus mediated asymmetric reduction of alkyl 3-oxobutanoates
-
t-Butyl 3-oxobutanoate gives the hydroxyester in ~68% yield and 99% ee. Alkyl 3-oxobutanoates (alkyl: methyl, ethyl, allyl, isobutyl, t-butyl) were reduced enantioselectively to the corresponding (S)-alcohols by the fungus Rhizopus arrhizus and other Rhizopus sp. The best result obtained was with t-butyl 3-oxobutanoate, which was reduced by R. arrhizus with 99% enantiomeric excess and ~68% isolated yield.
- Salvi, Neeta A.,Chattopadhyay, Subrata
-
p. 3397 - 3400
(2007/10/03)
-
- Chiral porous metal phosphonates for heterogeneous asymmetric catalysis
-
Chiral porous zirconium phosphonates containing metal complex moieties are provided, synthesized via a molecular building block approach, and characterized by a variety of techniques including TGA, adsorption isotherms, XRD, SEM, IR, and microanalysis. These hybrid solids may be used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with remarkably high e.e. values of up to 99.2%. Similarly prepared chiral porous solids may be used for asymmetric hydrogenation of β-keto esters with e.e.'s of up to 95%. The solid catalysts can also be easily recycled and reused multiple times without the loss of activity and enantioselectivity. Ready tunability of such a molecular building block approach allows the optimization of these hybrid materials to provide practically useful heterogeneous asymmetric catalysts.
- -
-
Page/Page column 9
(2010/02/08)
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- Synthesis of chiral β3-aminoxy peptides
-
A series of chiral β3-aminoxy acids or amides with various side chains have been synthesized via two different approaches. One is the Arndt-Eistert homologation approach, using chiral α-aminoxy acids as starting materials. The other approach, utilizing the enantioselective reduction of β-keto esters catalyzed by baker's yeast or chiral Ru(II) complexes, produces chiral β3-aminoxy acids with nonproteinaceous side chains. The oligomers of β3-aminoxy acids can be readily prepared using EDCI/HOAt as the coupling reagent.
- Yang, Dan,Zhang, Yu-Hui,Li, Bing,Zhang, Dan-Wei
-
p. 7577 - 7581
(2007/10/03)
-
- Mesoporous silica anchored Ru catalysts for highly enantioselective hydrogenation of β-ketoesters
-
Recyclable and reusable mesoporous silica anchored Ru catalysts based on 4,4′-substituted BINAPs were synthesized and used for the hydrogenation of β-alkyl β-ketoesters with up to 98.6% e.e. and β-aryl β-ketoesters with up to 95.2% e.e.
- Kesanli, Banu,Lin, Wenbin
-
p. 2284 - 2285
(2007/10/03)
-
- Chiral, Porous, Hybrid Solids for Highly Enantioselective Heterogeneous Asymmetric Hydrogenation of β-Keto Esters
-
Catalytic building blocks: Chiral porous zirconium phosphonates containing Rubinap moieties are synthesized by a molecular building-block approach, and characterized by a variety of techniques. These hybrid solids are used for enantioselective heterogeneous asymmetric hydrogenation of β-keto esters with ee values of up to 95% (see picture). Ready tunability of such a molecular building-block approach promises to lead to useful heterogeneous asymmetric catalysts.
- Hu, Aiguo,Ngo, Helen L.,Lin, Wenbin
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p. 6000 - 6003
(2007/10/03)
-
- Ruthenium(II)-Catalyzed Asymmetric Transfer Hydrogenation of Carbonyl Compounds with 2-Propanol and Ephedrine-Type Ligands
-
This account describes the development and application of Noyori's type catalysts based on ruthenium-arene complexes and simple chiral β-amino alcohols derived from ephedrine, for the asymmetric transfer hydrogenation of 2-propanol to carbonyl substrates. The influence of key parameters of the catalyst system has been studied systematically, resulting in particular in the design of the novel ligand (4-biphenylmethyl)norephedrine. Thanks to the latter, the catalytic precursors and true active species could be isolated for the first time, enabling a complete structural description of the catalytic cycle and of probable deactivation pathways. Highly effective applications of those catalysts systems, i.e., the asymmetric reductions of simple aryl ketones and aryl β-keto esters, the synthesis of chiral phthalides and syn-β,δ-dihydroxy esters, are described.
- Everacre, Kathelyne,Mortreux, André,Carpentier, Jean-Fran?ois
-
-
- (β-amino alcohol)(arene)ruthenium(II)-catalyzed asymmetric transfer hydrogenation of functionalized ketones - Scope, isolation of the catalytic intermediates, and deactivation processes
-
The asymmetric transfer hydrogenation of functionalized ketones with (β-amino alcohol)(arene)RuII catalysts using 2-propanol as the hydrogen source has been studied. The structure of the catalyst has been systematically screened using a wide variety of [(η6-arene)RuCl2]2 complexes and β-amino alcohols R1CH(OH)CHR2NHR3, some of which were specifically designed for optimized performance, e.g. (1S,2R)-N-(4-biphenylmethyl)norephedrine (9ο). The efficiencies of the catalytic combinations have been evaluated in the reduction of β-oxo esters and ketones bearing heteroatoms at the α-position. The catalyst precursor [{η6-p-cymene}{η2-N,O-(9ο)}RuCl] (35), the 16-electron true catalyst [{η6-p-cymene}{η2-N,O-(9ο1-) }Ru] (36), and the hydride [{η6-p-cymene}{η2-N,O-(9ο)}RuH] (37) involved in the reduction process have been isolated, characterized by NMR and ESI-MS, as well as by X-ray crystallography in the case of 35, and their reactivities have been investigated. The results reveal two general trends regarding this catalytic process: (1) the apparent reaction rate and the enantioselectivity are largely controlled by the nature of the amine functionality of the chiral ligand and the arene ring of the RuII precursor; (2) side reactions occur between the ketone substrate and the active catalytic species that affect the concentration of the latter and consequently the apparent rate; the formation of inactive (β-diketonato)RuII complexes is demonstrated in the case of β-oxo esters.
- Everaere, Kathelyne,Mortreux, André,Bulliard, Michel,Brussee, Johannes,Van Der Gen, Arne,Nowogrocki, Guy,Carpentier, Jean-Fran?ois
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p. 275 - 291
(2007/10/03)
-
- N-Benzyl-norephedrine derivatives as new, efficient ligands for ruthenium-catalyzed asymmetric transfer hydrogenation of functionalized ketones
-
Significant catalytic activities (up to 600 h-1 at 20°C) and enantiomeric excesses ranging from 56 to 89% for the asymmetric transfer hydrogenation of β-ketoesters, methoxyacetone and 2-acetylpyridine to the corresponding alcohols are achieved in the presence of catalytic combinations of [RuCl2(η6-arene)]2 and N-substituted derivatives of (1S,2R)- norephedrine such as N-benzyl-norephedrine and N-(4-biphenyl)methyl- norephedrine.
- Everaere, Kathelyne,Carpentier, Jean-Francois,Mortreux, Andre,Bulliard, Michel
-
p. 4083 - 4086
(2007/10/03)
-
- Asymmetric reduction of ketones by the acetone powder of Geotrichum candidum
-
Aromatic ketones, β-keto esters, and simple aliphatic ketones were reduced with excellent selectivity to the corresponding (S)-alcohols by using the acetone powder of Geotrichum candidum. This method is superior in reactivity and stereoselectivity to reduction by the whole-cell. The experimental conditions for the reduction system such as ratio of the biocatalyst to the substrate, kinds of coenzymes, alcohol for coenzyme regeneration, and buffer, pH, and reaction temperature were investigated, and stability and preservability of the biocatalyst were also examined. This method is very convenient for the synthesis of optically pure alcohols on a gram scale.
- Nakamura,Matsuda
-
p. 8957 - 8964
(2007/10/03)
-
- [2.2]PHANEPHOS-ruthenium(II) complexes: Highly active asymmetric catalysts for the hydrogenation of β-ketoesters
-
The application of the planar chiral [2.2]PHANEPHOS ligand in the Ru(II)-catalyzed asymmetric hydrogenation of β-ketoesters gave up to 96% ee involving a practical and reproducible procedure using the defined and readily prepared [2.2]PHANEPHOS-Ru(II)bis(trifluoroacetate) salt in the presence of a halide source.
- Pye, Philip J.,Rossen, Kai,Reamer, Robert A.,Volante,Reider, Paul J.
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p. 4441 - 4444
(2007/10/03)
-
- Synthesis and structure of linear and cyclic oligomers of 3- hydroxybutanoic acid with specific sequences of (R)- and (S)-configurations
-
To study the stereoselectivity of enzymatic cleavage of poly(3- hydroxybutyrates) (PHB) in a well-defined system (purified depolymerase and monodisperse substrate of specific relative configuration), linear and cyclic oligomers of HB (OHBs) containing (R)- and (S)-3-hydroxybutanoate residues were synthesized. The starting material (R)-HB was prepared from natural sPHB, and (S)-HB by enantioselective reduction of 3- oxobutanoate with yeast or with H2/Noyori-Taber catalyst (Scheme2). The HB building blocks were then prolected (O-benzyl/tert-butyl ester; Scheme 3) and coupled to give dimers 3, 4, tetramers 5-9, and octamers 10-18; for analytical comparison, a 3mer, 5mer, 6mer, and 7mer (19-22) were also prepared. Two of the tetramers were subjected to macrolactonization conditions (Yamaguchi) to give the cyclic tetramers 23 and 25 and octamers 24 and 26. All new compounds were fully characterized (m.p., [α](D), CD, IR, 1H- and 13C-NMR, MS, elemental analysis). Single-crystal X-ray structure analyses were performed with oligolides 24 and 25 (Figs. 2 and 4), and the structures, as well as the crystal packing, were compared with those of analogs containing only (R)-HB units or consisting of 3-amino- instead of 3-hydroxybutanoic-acid moieties.
- Bachmann, Beat M.,Seebach, Dieter
-
p. 2430 - 2461
(2007/10/03)
-
- The stereoselective preparation of β-hydroxy esters using a yeast reduction in an organic solvent
-
A range of (S)-β-hydroxy esters has been prepared in high yield (56-96%) and with very high enantioselectivity (>94%) using a yeast mediated reduction in light petroleum. It was found that the ester functionality had a marked effect on both the isolated yield and the quantity of yeast required to effect complete reduction.
- Medson, Caroline,Smallridge, Andrew J.,Trewhella, Maurie A.
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p. 1049 - 1054
(2007/10/03)
-
- Baker's yeast reduction of β-keto esters in petrol
-
A non-fermenting suspension of Baker's yeast in petrol containing a small amount of water reduces a variety of β-keto esters to the corresponding optically active β-hydroxy esters.
- North, Michael
-
p. 1699 - 1702
(2007/10/03)
-
- Asymmetric Reduction of 1-Acetoxy-2-alkanones with Baker's Yeast: Purification and Characterization of α-Acetoxy Ketone Reductase
-
An α-acetoxy ketone reducing enzyme has been purified and characterized from the cell-free extract of bakers' yeast (Saccharomyces cerevisiae). Only one NADPH-dependent dehydrogenase that catalyzed the reduction of α-acetoxy ketone was found in bakers' yeast. The molecular weight of the enzyme was estimated to be 36 kDa by SDS-polyacrylamide gel electrophoresis. The enzyme was composed of a single polypeptide chain. The enzyme had reducing activity for both aliphatic and aromatic α-acetoxy ketones, although no reducing activity toward α-chloro ketones and α-hydroxy ketones was found. The enzyme catalyzed the reduction of not only α-acetoxy ketones, but also β-keto esters. Studies on the chromatographic behavior and stereospecificity indicated that the enzyme was identical with one of the β-keto ester reductases purified from bakers' yeast.
- Ishihara, Kohji,Nakajima, Nobuyoshi,Tsuboi, Sadao,Utaka, Masanori
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p. 3314 - 3319
(2007/10/02)
-
- Asymmetric synthesis of both enantiomers of methyl and t-butyl 3-hydroxybutyrates monitored by optically active sulfoxides
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Methyl and t-butyl (R) and (S) 3-hydroxybutyrates were prepared by stereoselective reduction of (R) 4-[p-tolylsulfinyl]-3-oxobutyrate, readily available in one step from (-)(S) menthyl p-toluene sulfinate.
- Solladie, Guy,Almario, Antonio
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p. 2477 - 2480
(2007/10/02)
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- Asymmetric Reduction of Functionalized Ketones with a Sodium Borohydride-(L)-Tartaric Acid System
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The sodium borohydride-(L)-tartaric acid system is effective for the asymmetric reduction of prochiral ketones if they are functionalized on the α- or β-carbon with a group that can chelate to the chirally modified borohydride.
- Yatagai, Masanobu,Ohnuki, Takashi
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p. 1826 - 1828
(2007/10/02)
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- Enantiospecific synthesis of optically pure (3S)-hydroxy esters by the stereocontrolled yeast reduction of α-sulfenyl-β-ketoesters
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Stereocontrol in Baker's yeast reduction of β-ketoesters was successfully achieved by introducing the sulfenyl group at the α-position of the esters to afford optically pure (S)-β-hydroxy esters.
- Fujisawa,Itoh,Sato
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p. 5083 - 5086
(2007/10/02)
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- Enantiospecific Syntheses of Trifunctional (R)-3-Hydroxy Esters by Baker's Yeast Reduction
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Asymmetric syntheses of the enantiomerically pure trifunctional (R)-3-hydroxy esters (7)-(10) can be achieved by baker's yeast reduction of the hydrolysed β-keto carboxylates (2)-(5) instead of by reduction of the corresponding esters.
- Hirama, Masahiro,Shimizu, Mitsuaki,Iwashita, Mitsuko
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p. 599 - 600
(2007/10/02)
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- Ueber die Depolymerisierung von Poly-(R)-3-hydroxy-buttersaeureester (PHB)
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On the Depolimerization of Poly-(R)-3-hydroxy-butanoate (PHB): From cell-free PHB or from dried cells of Alcaligens eutrophus H 16, which had been grown in an aqueous fructose solution, enantiomerically pure methyl, ethyl, butyl or β-methoxyethyl (R)-3-hydroxy-butanoates are obtained in yields ranging from 75-90percent (0.1 to 70 g scale).The depolimerization is achieved by heating the PHB-containing materials to temperatures of 80-100 deg C in the corresponding alcohol with or without the cosolvent dichloroethane in the presence of either sulfuric acid or tetraethoxytitanium catalyst.Since (S)-3-hydroxy-butanoates are also readily obtained (by yeast reduction of aceto-acetates), starting materials derived from 3-hydroxy-butyric acid now belong to the especially useful group of synthetic building blocks which are available in both enantiomeric forms.
- Seebach, Dieter,Zueger, Max
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p. 495 - 503
(2007/10/02)
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