- The influence of wavelength of light on cyanobacterial asymmetric reduction of ketone
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Asymmetric reduction of ketone by a microalga, Synechocystis sp. PCC 6803, smoothly afforded to the corresponding (S)-alcohol in excellent enantiomeric excess by the aid of illumination of orange and red LED lights which are more effective than other LEDs
- Itoh, Ken-Ichi,Nakamura, Kaoru,Aoyama, Tadashi,Kakimoto, Tsuyoshi,Murakami, Masahiko,Takido, Toshio
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- Upregulation of an Artificial Zymogen by Proteolysis
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Regulation of enzymatic activity is vital to living organisms. Here, we report the development and the genetic optimization of an artificial zymogen requiring the action of a natural protease to upregulate its latent asymmetric transfer hydrogenase activity.
- Liu, Zhe,Lebrun, Vincent,Kitanosono, Taku,Mallin, Hendrik,K?hler, Valentin,H?ussinger, Daniel,Hilvert, Donald,Kobayashi, Shu,Ward, Thomas R.
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- Asymmetric Hydrogenation of Polysubstituted Aromatic Ketones Catalyzed by the DIPSkewphos/PICA Derivative–Ruthenium(II) Complexes
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The DIPSkewphos/PICA derivative-Ru(II) complexes catalyzed asymmetric hydrogenation of significantly sterically hindered 2’,3’,4’,5’,6’-pentamethylacetophenone, which was not reduced with NaBH4 at 25 °C, with a substrate-to-catalyst molar ratio
- Utsumi, Noriyuki,Arai, Noriyoshi,Kawaguchi, Kei,Katayama, Takeaki,Yasuda, Toshihisa,Murata, Kunihiko,Ohkuma, Takeshi
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- Light mediated cofactor recycling system in biocatalytic asymmetric reduction of ketone
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Reduction of an artificial ketone by Synechococcus elongatus PCC 7942 proceeds smoothly by the aid of light. The efficiency of the reaction is very high since the coenzyme NADPH is regenerated by using light energy.
- Nakamura, Kaoru,Yamanaka, Rio
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- Enantioselectivity in the Noyori?Ikariya asymmetric transfer hydrogenation of ketones
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Asymmetric transfer hydrogenation (ATH) is an important catalytic process in the fragrance and pharmaceutical industries. The Noyori?Ikariya chiral molecular ruthenium complex has been the catalyst of choice for this reaction for over 25 years. The mechan
- Dub, Pavel A.,Smith, Justin S.,Tkachenko, Nikolay V.,Tretiak, Sergei,Vyas, Vijyesh K.,Wills, Martin
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- Synthesis of novel oxazaborolidines B-C6F5 and their effectiveness as asymmetric catalysts
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Novel oxazaborolidines B-C6F5 were synthesized by modified protocol from C6F5B(OMe)2 (in place of usual C6F5B(OH)2) and the corresponding amino alcohols, aiming to kno
- Korenaga, Toshinobu,Kobayashi, Fuminao,Nomura, Kenji,Nagao, Shiho,Sakai, Takashi
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- Asymmetric synthesis of optically active fluorine-containing alcohols by the catalytic enantioselective alkylation of aldehydes
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Optically active fluorine-containing alcohols with up to 97% enantiomeric excess were synthesized by the enantioselective addition of dialkylzincs to fluorine-containing aldehydes using chiral β-aminoalcohol catalysts such as N,N-dibutylnorephedrine (DBNE
- Hayase, Tadakatsu,Sugiyama, Tadashi,Suzuki, Masanori,Shibata, Takanori,Soai, Kenso
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- One-pot Chemoenzymatic Deracemisation of Secondary Alcohols Employing Variants of Galactose Oxidase and Transfer Hydrogenation
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Enantiomerically enriched chiral secondary alcohols serve as valuable building blocks for drug intermediates and fine chemicals. In this study the deracemisation of secondary alcohols to generate enantiomeric pure chiral alcohols has been achieved by combining enantio-selective enzymatic oxidation of a secondary alcohol, by a variant of GOase (GOase M3-5), with either non-selective ketone reduction via transfer hydrogenation (TH) or enantio-selective asymmetric transfer hydrogenation (ATH). Both the enzymatic oxidation system and the transition-metal mediated reduction system were optimised to ensure compatibility with each other resulting in a homogeneous reaction system. 1-(4-nitrophenyl)ethanol was generated with 99 % conversion and 98 % ee by the deracemisation method, and it has been extended to a series of other secondary alcohols with comparable results.
- Yuan, Bo,Debecker, Damien P.,Wu, Xiaofeng,Xiao, Jianliang,Fei, Qiang,Turner, Nicholas J.
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p. 6191 - 6195
(2020/10/15)
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- Asymmetric Magnesium-Catalyzed Hydroboration by Metal-Ligand Cooperative Catalysis
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Asymmetric catalysis with readily available, cheap, and non-toxic alkaline earth metal catalysts represents a sustainable alternative to conventional synthesis methodologies. In this context, we describe the development of a first MgII-catalyzed enantioselective hydroboration providing the products with excellent yields and enantioselectivities. NMR spectroscopy studies and DFT calculations provide insights into the reaction mechanism and the origin of the enantioselectivity which can be explained by a metal-ligand cooperative catalysis pathway involving a non-innocent ligand.
- Falconnet, Alban,Magre, Marc,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 17567 - 17571
(2019/11/13)
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- Highly Enantioselective Transfer Hydrogenation of Prochiral Ketones Using Ru(II)-Chitosan Catalyst in Aqueous Media
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Unprecedentedly high enantioselectivities are obtained in the transfer hydrogenation of prochiral ketones catalyzed by a Ru complex formed in situ with chitosan chiral ligand. This biocompatible, biodegradable chiral polymer obtained from the natural chitin afforded good, up to 86 % enantioselectivities, in the aqueous-phase transfer hydrogenation of acetophenone derivatives using HCOONa as hydrogen donor. Cyclic ketones were transformed in even higher, over 90 %, enantioselectivities, whereas further increase, up to 97 %, was obtained in the transfer hydrogenations of heterocyclic ketones. The chiral catalyst precursor prepared ex situ was examined by scanning electron microscopy, FT-mid- and -far-IR spectroscopy. The structure of the in situ formed catalyst was investigated by 1H NMR spectroscopy and using various chitosan derivatives. It was shown that a Ru pre-catalyst is formed by coordination of the biopolymer to the metal by amino groups. This precursor is transformed in water insoluble Ru-hydride complex following hydrogen donor addition. The practical value of the developed method was verified by preparing over twenty chiral alcohols in good yields and optical purities. The catalyst was applied for obtaining optically pure chiral alcohols at gram scale following a single crystallization.
- Sz?ll?si, Gy?rgy,Kolcsár, Vanessza Judit
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p. 820 - 830
(2018/12/13)
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- Asymmetric Hydrogenation of Aryl Perfluoroalkyl Ketones Catalyzed by Rhodium(III) Monohydride Complexes Bearing Josiphos Ligands
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The asymmetric hydrogenation of 2,2,2-trifluoroacetophenones and aryl perfluoroalkyl ketones was developed using a unique, well-defined chloride-bridged dinuclear rhodium(III) complex bearing Josiphos-type diphosphine ligands. These complexes were prepared from [RhCl(cod)]2, Josiphos ligands, and hydrochloric acid. As catalyst precursors, they allow for the efficient and enantioselective synthesis (up to 99 % ee) of chiral secondary alcohols with perfluoroalkyl groups. This system does not require an activating base for the hydrogenation of 2,2,2-trifluoroacetophenones. Additionally, the enantioselective C=O hydrogenations of 2-phenyl-3-(haloacetyl)-indoles, a class of privileged structures in medicinal chemistry, is reported for the first time.
- Brüning, Fabian,Nagae, Haruki,K?ch, Daniel,Mashima, Kazushi,Togni, Antonio
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supporting information
p. 10818 - 10822
(2019/07/31)
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- Synthetic method for optical pure penta-fluo-phenethyl alcohol
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The invention relates to resolution of a phenethyl alcohol compound and especially relates to a synthetic method for optical pure penta-fluo-phenethyl alcohol, mainly aiming at solving the technical problems of long synthetic route of a penta-fluo-phenethyl alcohol asymmetric synthesis method and industrial use limitation of an enzymolysis resolution method. According to the technical scheme provided by the invention, the synthetic method for optical pure penta-fluo-phenethyl alcohol comprises the following steps: reducing pentafluoroacetophenone with sodium borohydride, reacting with phthalic anhydride to generate a benzoic acid derivative, and then chemically resolving the benzoic acid derivative with chiral phenylethylamine, removing phenylethylamine with diluted hydrochloric acid, resolving the phthalic acid group with alkali, extracting, drying, filtering and concentrating, thereby acquiring the optical pure penta-fluo-phenethyl alcohol product.
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- Mechanism-Based Enantiodivergence in Manganese Reduction Catalysis: A Chiral Pincer Complex for the Highly Enantioselective Hydroboration of Ketones
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A manganese alkyl complex containing a chiral bis(oxazolinyl-methylidene)isoindoline pincer ligand is a precatalyst for a catalytic system of unprecedented activity and selectivity in the enantioselective hydroboration of ketones, thus producing preparatively useful chiral alcohols in excellent yields with up to greater than 99 % ee. It is applicable for both aryl alkyl and dialkyl ketone reduction under mild reaction conditions (TOF >450 h?1 at ?40 °C). The earth-abundant base-metal catalyst operates at very low catalyst loadings (as low as 0.1 mol %) and with a high level of functional-group tolerance. There is evidence for the existence of two distinct mechanistic pathways for manganese-catalyzed hydride transfer and their role for enantiocontrol in the selectivity-determining step is presented.
- Vasilenko, Vladislav,Blasius, Clemens K.,Wadepohl, Hubert,Gade, Lutz H.
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p. 8393 - 8397
(2017/07/11)
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- Copper-dipyridylphosphine-polymethylhydrosiloxane: A practical and effective system for the asymmetric catalytic hydrosilylation of ketones
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In the presence of the inexpensive and non-toxic stoichiometric reductant polymethylhydrosiloxane (PMHS), the chiral copper(II)-dipyridylphosphine catalyst displayed high efficiency in the stereoselective hydrosilylation of a wide scope of aryl alkyl and heteroaromatic ketones under an air atmosphere and mild conditions in good to excellent ees (up to 97%). With certain amounts of sodium tert-butoxide and tert-butyl alcohol as additives, the reaction on a 21-g substrate scale can be conveniently completed within a few hours even at a substrate-to-ligand (S/L) ratio of 50,000. Copyright
- Zhang, Xi-Chang,Wu, Fei-Fei,Li, Shijun,Zhou, Ji-Ning,Wu, Jing,Li, Ning,Fang, Wenjun,Lam, Kim Hung,Chan, Albert S. C.
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supporting information; experimental part
p. 1457 - 1462
(2011/08/03)
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- Cobalt(II)-catalyzed asymmetric hydrosilylation of simple ketones using dipyridylphosphine ligands in air
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In the presence of PhSiH3 as the hydride donor, catalytic amounts of non-racemic dipyridylphosphine and an easy-to-handle cobalt salt Co(OAc)2·4H2O formed in situ an effective catalyst system for the asymmetric reduction o
- Yu, Feng,Zhang, Xi-Chang,Wu, Fei-Fei,Zhou, Ji-Ning,Fang, Wenjun,Wu, Jing,Chan, Albert S. C.
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supporting information; experimental part
p. 5652 - 5654
(2011/09/15)
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- Asymmetric hydroboration and Matteson homologation for the preparation of fluorinated α-phenethanols
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The asymmetric catalytic hydroboration-oxidation of ring-fluorinated styrenes (F-PhCH{double bond, long}CH2) was achieved with catecholborane along with a combination of [Rh(COD)2]+BF4- and (R)-BINAP providing 81-96% enantioselectivities for the product alcohols for ortho-unhindered styrenes. A deleterious effect of a 2,6-disubstitution on the enantioselectivity of the product alcohol was observed. 2-Trifluoromethylstyrene also provides only 53% ee, probably due to the steric bulk of the CF3 group at the ortho-position of styrene. Asymmetric homologation of fluorophenylmetals (magnesium bromide or lithium) with pinanediol α-chloroethylboronate, followed by oxidation readily furnished the desired 1-(2,6-difluorophenyl)- and 1-(perfluorophenyl)ethanols in 94-95% ee.
- Ramachandran, P. Veeraraghavan,Jennings, Michael P.
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p. 827 - 831
(2008/03/14)
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- Combined ruthenium(II) and lipase catalysis for efficient dynamic kinetic resolution of secondary alcohols. Insight into the racemization mechanism
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Pentaphenylcyclopentadienyl ruthenium complexes (3) are excellent catalysts for the racemization of secondary alcohols at ambient temperature. The combination of this process with enzymatic resolution of the alcohols results in a highly efficient synthesis of enantiomerically pure acetates at room temperature with short reaction times for most substrates. This new reaction was applied to a wide range of functionalized alcohols including heteroaromatic alcohols, and for many of the latter, enantiopure acetates were efficiently prepared for the first time via dynamic kinetic resolution (DKR). Different substituted cyclopentadienyl ruthenium complexes were prepared and studied as catalysts for racemization of alcohols. Pentaaryl-substituted cyclopentadienyl complexes were found to be highly efficient catalysts for the racemization. Substitution of one of the aryl groups by an alkyl group considerably slows down the racemization process. A study of the racemization of (S)-1-phenylethanol catalyzed by ruthenium hydride η5-Ph5CpRu(CO) 2H (8) indicates that the racemization takes place within the coordination sphere of the ruthenium catalyst. This conclusion was supported by the lack of ketone exchange in the racemization of (S)-1-phenylethanol performed in the presence of p-tolyl methyl ketone (1 equiv), which gave 1% of 1-(p-tolyl)ethanol. The structures of ruthenium chloride and iodide complexes 3a and 3c and of ruthenium hydride complex 8 were confirmed by X-ray analysis.
- Martin-Matute, Belen,Edin, Michaela,Bogar, Krisztian,Kaynak, F. Betuel,Baeckvall, Jan-E.
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p. 8817 - 8825
(2007/10/03)
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- Origin of enantioselectivity in the Ru(arene)(amino alcohol)-catalyzed transfer hydrogenation of ketones
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The origin of the enantioselectivity in the ruthenium-catalyzed transfer hydrogenation has been studied by means of experiment and density functional theory calculations. The results clearly show that electrostatic effects are of importance, not only in the T-shaped arene-aryl interaction in the favored transition state but also between the aryl of the substrate and the amine ligand in the disfavored TS. In addition, the electrostatic interaction between the alkyl substituent of the substrate and the catalyst is of importance to the enantioselectivity. The major cause of enantioselection is found to be of nonelectrostatic origin. This inherent property of the catalytic system is discussed in terms of dispersion forces and solvent effects. Finally, a minor but well-characterized steric effect was identified. The success of this class of catalysts in the reduction of alkyl aryl ketones is based on the fact that all factors work in the same direction.
- Brandt, Peter,Roth, Peter,Andersson, Pher G.
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p. 4885 - 4890
(2007/10/03)
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- Mechanism-based enzymatic method for reliable determination of absolute configuration of chiral 1-substituted ethanols: Combination with NMR method
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It has been demonstrated that lipase is useful not only for kinetic resolution but also for the rapid determination of absolute configurations. We have previously proposed a mechanism represented by transition-state models to rationalize the enantioselect
- Ema, Tadashi,Yoshii, Masataka,Korenaga, Toshinobu,Sakai, Takashi
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p. 1223 - 1229
(2007/10/03)
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- A new catalytic enantioselective reducing reagent system from (-)-α,α-diphenylpyrrolidinemethanol and 9-borabicyclo[3.3.1]nonane, especially effective for hindered and substituted aralkylketones
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New catalytic enantioselective reduction systems were prepared from aminoalcohols and dialkylboranes, for the enantioselective reductions of prochiral aromatic ketones. Among these, the system prepared from (-)-α,α-diphenylpyrrolidinemethanol with 9-borabicyclo[3.3.1]nonane proved especially promising for such reductions. This complex catalyzes the reduction of prochiral aralkyl ketones to the corresponding alcohols with BH3-THF, with enantioselectivities 82-99.2%. Also, this catalyst is particularly effective for the more hindered and substituted aralkyl ketones. Various modifications in this new catalytic reduction system, such as changing reaction conditions, reducing agent and dialkylborane, were also examined.
- Kanth, Josyula V.B.,Brown, Herbert C.
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p. 1069 - 1074
(2007/10/03)
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- Cyanobacterium-catalyzed asymmetric reduction of ketones
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Synechococcus sp. PCC 7942, a cyanobacterium, acted as a biocatalyst to reduce aryl methyl ketones into the corresponding (S)-alcohols with excellent enantioselectivities under illumination. (C) 2000 Elsevier Science Ltd.
- Nakamura, Kaoru,Yamanaka, Rio,Tohi, Keiko,Hamada, Hiroki
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p. 6799 - 6802
(2007/10/03)
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- Two Classes of Enzymes of Opposite Stereochemistry in an Organism: One for Fluorinated and Another for Nonfluorinated Substrates
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Reduction of methyl ketones by dried cells of Geotrichum candidum (APG4) afforded (S)-alcohols in excellent enantiomeric excess (ee), whereas the reduction of trifluoromethyl ketones gave the corresponding alcohols of the opposite configuration also in excellent ee. The replacement of the methyl moiety with a trifluoromethyl group alters both the bulkiness and the electronic properties, the effect of which on the stereoselectivity was examined. No inversion in stereochemistry was observed in the reduction of hindered ketones such as isopropyl ketone, while the stereoselectivity was inverted in the reduction of ketones with electron-withdrawing atoms such as chlorine. The mechanism for the inversion in stereochemistry was investigated by enzymatic studies. Several enzymes with different stereoselectivities were isolated; one of them catalyzed the reduction of methyl ketones, and another with the opposite stereoselectivity catalyzed the reduction of trifluoromethyl ketones. Furthermore, both APG4 and the isolated enzyme were applied to the reduction of fluorinated ketones on a preparative scale, which resulted in the synthesis of chiral fluorinated alcohols with excellent ee.
- Matsuda, Tomoko,Harada, Tadao,Nakajima, Nobuyoshi,Itoh, Toshiyuki,Nakamura, Kaoru
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p. 157 - 163
(2007/10/03)
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- Asymmetric reduction of ketones by the acetone powder of Geotrichum candidum
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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
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p. 8957 - 8964
(2007/10/03)
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- Pentafluorophenyl derivatives, methods of production thereof, and method of optical resolution of chiral carboxylic acids
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Pentafluorophenyl derivatives are expressed by the formula (I): STR1 where X represents an alkyl group having from 1 to 4 carbon atoms or a halogen atom; Y represents any group of --CH2 OH, --COOH, --COCl, --CON1 R2, or --
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- Asymmetric synthesis of α-methyl carboxylic acid derivatives stereochemistry in acidic ring opening of epoxides
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Optically active α-methyl carboxylic acid derivatives were prepared via reaction of microbially produced epoxides with trimethylaluminum. Stereochemistry of the ring opening reaction was discussed through an MO calculation.
- Fukumasa,Furuhashi,Umezawa,Takahashi,Hirai
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p. 1059 - 1062
(2007/10/02)
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- (S)-(-)- and (R)-(+)-1-(Pentafluorophenyl)ethanol
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The preparation of enantiomerically pure (ee >/= 94percent) (S)-(-)- and (R)-(+)-1-(pentafluorophenyl)ethanol by enantioselective synthesis and optical resolution is described.
- Meese, Claus O.
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p. 2004 - 2007
(2007/10/02)
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