- Normal Pressure Double Carbonylation of Aryl Halides Using Cobalt(II) Chloride in the Presence of either Sodium Sulfide or Sodium Borohydride
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Tetracarbonylcobaltate ion generated by a treatment of cobalt(II) chloride with either sodium sulfide or sodium borohydride under a normal pressure of carbon monoxide was capable of catalyzing carbonylation of aryl halides in the presence of calcium hydroxide and methyl iodide to give arylglyoxylic acids in good selectivity.
- Itoh, Kenji,Miura, Masahiro,Nomura, Masakatsu
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- Ultrasonically-promoted synthesis of mandelic acid by phase transfer catalysis in an ionic liquid
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An efficient and facile process to synthesize mandelic acid through phase transfer catalysis (PTC; also phase transfer catalyst) using ultrasound in an ionic liquid has been developed. Mandelic acid was synthesized from benzaldehyde with chloroform in an
- Hua, Qian,Dabin, Liu,Chunxu, Lv
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- A combination of phase transfer catalyst and ultrasonic irradiation promotes synthesis of mandelic acid
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A combination of phase transfer catalyst and ultrasonic irradiation used to promotes synthesis of mandelic acid from benzaldehyde with chloroform. The main advantages of this method are that the reaction time is much shorter and the yield is higher than t
- Zhang, Yu-Quan,Zheng, Xu-Dong,Gai, Ke,Li, Yan-Chun,Cheng, Dong-Ping
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- Effect of the concentration of organic modifier in an aqueous-ethanol mobile phase on the chromatographic retention and thermodynamic characteristics of the adsorption of enantiomers of α-phenylcarboxylic acids on silica gel with immobilized eremomycin antibiotic
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Regularities of the chromatographic retention and thermodynamics of the adsorption of enantiomers of α-phenylcarboxylic acids on a chiral stationary phase with immobilized macrocyclic antibiotic eremomycin under conditions of reversed-phase liquid chromatography with aqueous-ethanol mobile phases are studied. Relationships between the retention characteristics of the acids, the enantioselectivity of their separation, and the concentration of organic modifier in the mobile phase are found. It is shown that the sterical structure of substituents on the chiral atoms of the acids affect the mechanism of retention. The compensation effect in the studied systems is considered.
- Blinov,Reshetova
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- Improved solution- and solid-phase preparation of hydroxamic acids from esters
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The addition of small amounts of solid KCN to solution and solid-phase esters in THF/MeOH/50% aqueous NH2OH increases the efficiency of their transformation to the corresponding hydroxamic acids.
- Ho, Chih Y.,Strobel, Eric,Ralbovsky, Janet,Galemmo Jr., Robert A.
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- Solvent-induced reversed stereoselectivity in reciprocal resolutions of mandelic acid and erythro -2-amino-1,2-diphenylethanol
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Solvent-induced chirality switching in reciprocal optical resolution between mandelic acid (1) and erythro-2-amino-1,2-diphenylethanol (2) has been demonstrated. The stereochemistry of the deposited salts was controlled by changing the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane. It was revealed from 1H NMR spectra, thermogravimetric analysis, and X-ray crystallography of the salts that an equimolar amount of the crystallization solvent was incorporated in each diastereomeric salt. On the basis of the crystal structures, it was found that both the hydrogen-bonding ability and the size of the solvent molecule played an important role. Differences in the formed hydrogen-bonding networks (columnar or sheetlike structure) and their packing manner were found to be crucial for the reversed stereoselectivity. Furthermore, pseudopolymorphic salt crystals that incorporated 1,4-dioxane were obtained during the enantioseparation of racemic 2, and their solid-state properties were examined by measurement of their IR spectra. This solvent-induced dual stereocontrol technique was successfully applied to the successive resolution process, eliminating the need to change the resolving agent for access to both enantiomers of 1 and 2.
- Shitara, Hiroaki,Shintani, Toshiki,Kodama, Koichi,Hirose, Takuji
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- Effect of Alkaloid Concentration in Asymmetric Electrosynthesis
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The preferred absolute configurations of mandelic acid and C-phenylglycine, obtained from the asymmetric electroreduction of phenylglyoxylic acid and the related oxime in the presence of adsorbed strychnine acting as a chiral inductor, depend on the alkaloid concentration.
- Jubault, Michel
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- Medium effects on Zwitterionic-biradicaloid intermediates from two phenyl-α-oxoamides. Irradiations in fluid and solid protic media, neat solid phases, and the solid, smectic and isotropic phases of a completely saturated phosphonium salt at different tem
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The photochemical processes of two N,N-dialkyl phenyl-α-oxoamides, N,N-diisopropyl phenyl-α-oxoamide (1) and N,N-dibenzyl phenyl-α-oxoamide (2), are investigated at different temperatures in methanol and ethylene glycol (to probe the influences of H-bondi
- Chesta, Carlos A.,George, Mathew,Luo, Chuping,Weiss, Richard G.
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- Light-assisted preparation of a cyclodextrin-based chiral stationary phase and its separation performance in liquid chromatography
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A cyclodextrin-based chiral stationary phase (CD-CSP) is one of the most widely applied CSPs due to its powerful enantioseparation ability. In this study, a facile method was developed to prepare a CD-CSP via carboxyl methyl β-cyclodextrin (CD-COOH) and diazo-resin (DR). Monodisperse silica particles were synthesized using a modified St?ber method. Then DR and CD-COOH were coated on the silica particles via ionic bonding successively and UV light was finally used to couple silica, DR and CD-COOH and the ionic bonds turned into covalent bonds. The resultant CD-DR silica particles were characterized using Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). The enantioselectivity of the CD@SiO2 particles was explored in reversed phase high-performance liquid chromatography (RP-HPLC). Baseline separation of chiral drugs was achieved and the effects of separation parameters (elution mode, buffer and analyte mass) were investigated in detail. By using water soluble non-toxic DR to replace a highly toxic and moisture sensitive silane agent to modify silica microspheres, this light-assisted strategy can provide a green and effective technique to manufacture packing materials for enantioseparation applications.
- Tang, Qi,Yu, Bing,Gao, Lilong,Cong, Hailin,Zhang, Shuai
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- Biocatalysis for sustainable organic synthesis
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Biocatalysis offers mild reaction conditions, an environmentally attractive catalyst-solvent system, high activities, and chemo-, regio-, and stereoselectivities, while the use of enzymes generally circumvents the need for functional group activation and
- Sheldon, Roger A.,Van Rantwijk, Fred
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- Designing of amino functionalized imprinted polymeric resin for enantio-separation of (±)-mandelic acid racemate
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S-Mandelic acid (MA) enantio-selective resinous material functionalized with –NH2 groups has been developed and effectively utilized in chiral separation of (±)-MA racemate solution. S-MA has first combined with the polymerizable p-aminophenol and form the corresponding amide derivative, which was then polymerized with phenol/formalin using HCl as a catalyst. The stereo-selective –NH2 functionalized binding sites were then generated within the resin upon the alkaline degradation of the amide linkages followed by acidic treatments that will expel the resin incorporated S-MA out of the polymeric material to get the S-MA imprinted polymer (S-MAPR). The synthesized S-MA chiral amide derivative along with the developed polymeric resin was investigated by various techniques including FTIR and NMR spectra that confirmed the executed chemical modifications. In addition, the morphological appearance of the obtained resins were observed using SEM images. Moreover, the S-MAPR resin was examined to optimize the enantio-selective separation conditions and the studies indicated that the adsorption reached the highest value at pH 7 and the maximum capacity was 243 ± 1 mg/g. In addition, the chiral separation of (±)-MA racemic solution was successfully executed by the S-MAPR separation column with 55% and 82% enantiomeric excess of R- and S-MA within both the initial loading and recovery eluant solutions, respectively.
- Alhawiti, Aliyah S.,Monier,Elsayed, Nadia H.
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- Highly enantioselective biocatalysts by coating immobilized lipases with polyethyleneimine
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Polyethyleneimine (PEI) modification on immobilized lipases greatly enhanced their enantioselectivity in the kinetic resolution of (±)-2-hydroxy-phenylacetic acid methyl ester. The enantiomeric ratio (E) of CNBragarose-CRL rose from 8 (without coating) to 20 (ee=90%) after PEI coating in the hydrolysis at pH 5. In the case of CAL-B, the coating highly improved the enantioselectivity of the immobilized lipase from E=1.5 (without coating) to E>100 (ee>99%). Moreover, this coating strategy improved the stability of the biocatalyst at high temperatures and in the presence of high co-solvent concentrations.
- Cabrera, Zaida,Gutarra, Melissa L.E.,Guisan, Jose M.,Palomo, Jose M.
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- Whole Cell-Based Cascade Biotransformation for the Production of (S)-Mandelic Acid from Styrene, L-Phenylalanine, Glucose, or Glycerol
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(S)-Mandelic acid is a useful and high value chemical with many synthetic applications, but its synthesis often requires the use of toxic cyanide. Here, we report the development of several cyanide-free methods to prepare (S)-mandelic acid via cascade biotransformation. Enhanced production of (S)-mandelic acid from styrene via 4-step enzyme cascades was achieved with Escherichia coli (A-M1_R-M2) cells, giving 118–144 mM (18–21.9 g/L, 72–79% yield) product. The process was scaled up to 1.5 L to produce 140 mM (21.3 g/L) of (S)-mandelic acid in 70% yield. A strategy with the recycling and reuse of Escherichia coli cells, unreacted substrate, and organic solvent was developed to enhance the productivity of (S)-mandelic acid through repeated batches, affording 190 mM (95% yield) and 328 mM (82% yield) product in two and four batches, respectively. (S)-mandelic acid was also produced from bio-derived L-phenylalanine via 6-step enzyme cascades. Biotransformation of L-phenylalanine with Escherichia coli (LZ37) cells expressing all enzymes for the reactions gave 160 mM (S)-mandelic acid in 80% yield. Moreover, (S)-mandelic acid were synthesized from glycerol or glucose via L-phenylalanine biosynthesis pathway and the 6-step enzyme cascade. Coupling of Escherichia coli (NST74-Phe) with Escherichia coli (LZ37) enabled the sustainable production of 63 mM (10 g/L) or 52 mM (8 g/L) (S)-mandelic acid from renewable feedstocks glycerol and glucose, respectively. (Figure presented.).
- Lukito, Benedict Ryan,Sekar, Balaji Sundara,Wu, Shuke,Li, Zhi
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- ACID-CATALYZED HYDROLYSIS OF PHENYLDIAZOACETIC ACID. EFFECT OF AN α-DIAZO GROUP ON CARBOXYLIC ACID ACIDITY
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rates of acid-catalyzed hydrolysis of phenyldiazoacetic acid were measured in aqueous solution at 25 deg C across the entire acidity range pCH+ - 1-13.The reaction was found to occur through both the non-ionized and ionized forms of the substra
- Kresge, A.J.,Mathew, L.,Popik, V.V.
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- Asymmetric ammonolysis of (R/S)-mandelic acid by immobilized lipases via direct amidation of mandelic acid in biphasic media
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We have investigated the direct enantioselective amidation of mandelic acid with ammonia, catalyzed by a variety of commercial lipases including those from Candida rugosa, Mucor miehei, Pseudomonas sp., Rhizomucor miehei, and Thermomyces lanuginosus coval
- Yildirim, Deniz,Tükel, S. Seyhan
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- Construction of Recombinant Escherichia coli catalysts which simultaneously express an (S)-oxynitrilase and different nitrilase variants for the synthesis of (S)-mandelic acid and (S)-mandelic amide from benzaldehyde and cyanide
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Recombinant Escherichia coli strains were constructed which simultaneously expressed the genes encoding the (S)-oxynitrilase from cassava (Manihot esculenta) together with the wild-type or a mutant variant of the arylacetonitrilase from Pseudomonas fluorescens EBC191 in a single organism under the control of a rhamnose-inducible promoter. The whole cell catalysts obtained converted benzaldehyde and potassium cyanide in aqueous media at pH 5.2 mainly to (S)-mandelic acid and/or (S)-mandelic amide and synthesized only low amounts of the corresponding (R)-enantiomers. The conversion of benzaldehyde and potassium cyanide (KCN) by a whole-cell catalyst simultaneously expressing the (5)-oxynitrilase and the wild-type nitrilase resulted in a ratio of (S)-mandelic acid to (S)-mandelic amide of about 4:3. This could be explained by the strong nitrile hydratase activity of the wild-type nitrilase with (S)-mandelonitrile as substrate. The relative proportion of (S)-mandelic amide formed in this system was significantly increased by coexpressing the (S)-oxynitrilase with a carboxy-terminally truncated variant of the nitrilase. This whole-cell catalyst converted benzaldehyde and KCN to mandelic amide and mandelic acid in a ratio of about 9:1. The ee of the (S)-mandelic amide formed was calculated to be 95%.
- Sosedov, Olga,Matzer, Kathrin,Buerger, Sibylle,Kiziak, Christoph,Baum, Stefanie,Altenbuchner, Josef,Chmura, Andrzej,Van Rantwijk, Fed,Stolz, Andreas
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- Chiral Polymers of Intrinsic Microporosity: Selective Membrane Permeation of Enantiomers
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Following its resolution by diastereomeric complexation, 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) was used to synthesize a chiral ladder polymer, (+)-PIM-CN. (+)-PIM-COOH was also synthesized by the acid hydrolysis of (+)-PIM-CN. Following characterization, both (+)-PIM-CN and (+)-PIM-COOH were solvent cast directly into semipermeable membranes and evaluated for their ability to enable the selective permeation of a range of racemates, including mandelic acid (Man), Fmoc-phenylalanine, 1,1′-bi-2-naphthol (binol), and TTSBI. High ee values were observed for a number of analytes, and both materials exhibited high permeation rates. A selective diffusion–permeation mechanism was consistent with the results obtained with these materials. Their high permeability, processability, and ease of chemical modification offer considerable potential for liquid-phase membrane separations and related separation applications.
- Weng, Xilun,Baez, José E.,Khiterer, Mariya,Hoe, Madelene Y.,Bao, Zongbi,Shea, Kenneth J.
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- A photocatalytic acid- and base-free Meerwein-Ponndorf-Verley-type reduction using a [Ru(bpy)3]2+/viologen couple
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A photocatalytic system to effect the Meerwein-Ponndorf-Verley reduction of carbonylic compounds to alcohols has been developed. The system comprises [Ru(bpy)3]2+ as a photosensitizer, triethanolamine as a sacrificial electron donor,
- Herance, Jose Raul,Ferrer, Belen,Bourdelande, Jose Luis,Marquet, Jordi,Garcia, Hermenegildo
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- Novel catalytic tandem isomerisation/cyclisation reaction of α-methallyloxy carboxylic acids
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A new tandem isomerisation/cyclisation of α-methallyloxy carboxylic acids leading to substituted 1,3-dioxolan-4-ones in 60-70 % yields was catalysed by Cu(OTf)2 or Al(OTf)3. Extension to the synthesis of oxathiolanones and oxathianon
- Chaminade, Xavier,Coulombel, Lydie,Olivero, Sandra,Dunach, Elisabet
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- Purification and improvement of the functional properties of Rhizopus oryzae lipase using immobilization techniques
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The adsorption/immobilization of Rhizopus oryzae lipase (ROL) has permitted the development of several strategies to improve the properties of this industrial enzyme. The enzyme can be purified, immobilized, hyperactivated and stabilized, though its enantioselectivity could still be improved. A moderately hydrophobic support (e.g., phenyl-Toyopearl) allows the almost-quantitative immobilization of the enzyme via selective hydrophobic adsorption, while any contaminant proteins are not adsorbed. A further desorption of the adsorbed enzyme with surfactants (e.g., 0.5% sucrose laurate) allows the complete purification of the enzyme in only one step, with a 90% purification yield and an 8-fold purification factor. By using a more hydrophobic support, the ROL can be immobilized and hyperactivated. The enzyme is completely adsorbed on octyl-Sepharose and C18-Sepabeads. The pure enzyme (when adsorbed on these supports) becomes hyperactivated to approximately 250% of the activity of the soluble enzyme. In this study, two protocols for the covalent immobilization of ROL were developed: a one-point immobilization on CNBr-activated Sepharose and a multipoint covalent immobilization on highly activated glyoxyl-agarose supports. The multipoint attached enzyme decreased in activity to 50% of the activity of the soluble enzyme, but the derivatives were 300-fold more stable than the soluble enzyme. The hydrolysis of racemic 2-O-butyryl-2-phenylacetic acid was modulated by the different immobilized derivatives. In fact, the most active and selective preparation was demonstrated to be the C18-SB-ROL derivative (0.05 UI/mg and E = 22) when compared with the CNBr-ROL enzyme preparation (0.0073 UI/mg and E = 3.5).
- Ghattas,Filice,Abidi,Guisan,Ben Salah
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- Enantioseparation of mandelic acid and α-Cyclohexylmandelic acid using an alcohol/salt-based aqueous two-Phase system
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An alcohol/salt-based aqueous two-phase system (ATPS) was employed for enantioseparation of (R,S)-mandelic acid (MA) and (R,S)-a-cyclohexylmandelic acid (a-CHMA). Sulfonated β-cyclodextrin (Sf-β-CD) with different degrees of substitution (DS) was consider
- Li, Fen-Fang,Tan, Zhi-Jian,Guo, Zhi-Feng
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- Enantioseparation of mandelic acid and substituted derivatives by high-performance liquid chromatography with hydroxypropyl-β-cyclodextrin as chiral mobile additive and evaluation of inclusion complexes by molecular dynamics
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The enantioseparation and resolution mechanism of mandelic acid (MA), 4-methoxymandelic acid (MMA), and 4-propoxymandelic acid (PMA) were investigated by reversed-phase high-performance liquid chromatography (HPLC) with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) as a chiral mobile-phase additive and molecular dynamics simulation. The suitable chromatographic conditions for the enantioseparation of MA, MMA, and PMA were obtained. Under the selected chromatographic conditions, these enantiomers could achieve baseline separation. The results of thermodynamic parameter analysis revealed that the main driven forces for the enantioseparation of MA, MMA, and PMA could be van der Waals forces and hydrogen-bonding interactions and the chromatographic retention of these chiral compounds was an enthalpy-driven process. The results of the molecular simulation revealed that their chiral resolution mechanism on HP-β-CD was responsible for the formation of inclusion complexes of enantiomers with HP-β-CD with different conformations and binding energies. And the binding energy of HP-β-CD with (S)-isomer was larger than that with (R)-isomer, which is consistent with the experimental results of the first elution of (S)-isomer. Additionally, it is also confirmed that the interaction energies included the van der Waals energy (?Evdw), electrostatic energy (?Eelec), polar solvation energy, and SASA energy (?Esasa), and the separation factor (α) was closely connected with the disparity in the binding energies of optical isomers and HP-β-CD complexes. Meanwhile, from molecular dynamics simulation, it can be found that the ?(?Ebinding), (?(?Ebinding) = ?Ebinding,R ? ?Ebinding,S) value was in order of MA–HP-β-CD complex > MMA–HP-β-CD complex > PMA–HP-β-CD complex, which was consistent with the order of Δ(ΔG) values obtained from van't Hoff plot. This indicated that the molecular dynamics simulation has predictive function for chiral resolution.
- Shi, Jie-Hua,Lin, Zhen-Yi,Kou, Song-Bo,Wang, Bao-Li,Jiang, Shao-Liang
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- Direct enantioseparation of mandelic acid by high-performance liquid chromatography using a phenyl column precoated with a small amount of cyclodextrin additive in a mobile phase
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Direct enantioseparation of mandelic acid by high-performance liquid chromatography (HPLC) with a reversed phase column and a mobile phase containing a small amount of hydroxylpropyl-β-cyclodextrin (HP-β-CD) was studied as an efficient method for saving consumption of the CD additive. As a result, it was proposed that racemic mandelic acid can be analyzed with a phenyl column by using a mobile phase composed of 10 mM ammonium acetate buffer (pH 4.2) and 0.02% (w/v) HP-β-CD at a flow rate of 1.0 mL/min at 40°C after the passage of 10 mM ammonium acetate buffer (pH 4.2) containing 0.1% (w/v) HP-β-CD as a precoating mobile phase for 60 min. It is suggested that HP-β-CD is bound with a phenyl group on the surface of the stationary phase to allow a phenyl column to act as a transient chiral column, and injected mandelic acid can form the ternary complex with the adsorbed HP-β-CD. The longer retention time of D-mandelic acid than the L-isomer for HPLC can be explained from the higher stability of the HP-β-CD complex with D-mandelic acid, which was confirmed by CE experiment with HP-β-CD as a selector. The efficiency of a phenyl column compared with other stationary phases was also discussed.
- Watanabe, Yuri,Mikami, Ikko,Yamamoto, Atsushi,Aizawa, Sen-ichi,Taga, Atsushi,Mochizuki, Naoki,Ishihara, Yoshimi,Kodama, Shuji
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- Aerial oxidation of the glucocorticoid side-chain under pH control
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The outcome of aerial oxidation of the glucocortico-steroid side-chain (as exemplified by dexamethasone) has been shown to be subject to strict pH control. At pH 7.4 the glyoxal is the only product; at pH values of 8 and 9.2 the etioacid is formed, and at
- Edmonds, John S.,Morita, Masatoshi,Turner, Peter,Skelton, Brian W.,White, Allan H.
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- Electrocatalytic reduction of benzoylformic acid mediated by methyl viologen
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Benzoylformic acid is reduced electrocatalytically to mandelic acid in excellent yield in the presence of methyl viologen of which two-electron reduction product behaves as active reductant, and the presence of β-CD or its derivative induces enantioselect
- Park, Joon Woo
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- The pH-dependency of diastereomeric salt resolutions with amphoteric resolving agents
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We have analysed the role of pH in the diastereomeric resolution of racemic mandelic acid with (S)-phenylalanine and (R)-3-(aminomethyl)- 5-methylhexanoic acid [(R)-Pregabalin] enantiomers. The adjusted pH had an effect on the optical purity and yield of
- Szeleczky, Zsolt,Bagi, Péter,Pálovics, Emese,Faigl, Ferenc,Fogassy, Elemér
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- Chirality switching in optical resolution of mandelic acid in C1-C4 alcohols: Elucidation of solvent effects based on x-ray crystal structures of diastereomeric salts
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Chirality switching in the optical resolution of mandelic acid (MA) using (1R,2S)-2-amino-1,2-diphenylethanol (ADPE) in C1-C4 alcohols is demonstrated herein. Recrystallization of the diastereomeric mixture of the MA salts from longer alcohol solvents (n-PrOH, s-BuOH, i-BuOH, and n-BuOH) produced the (R)-MA salt, whereas the (S)-MA salt was preferentially deposited from shorter alcohol solvents (MeOH, EtOH, i-PrOH, and t-BuOH). Thermogravimetric analysis and 1H NMR spectroscopy showed that all the solvents employed were incorporated in the diastereomeric salts and the stability of the incorporated alcohols increased with an increase in the effective surface area of their alkyl chains. The X-ray crystal structures of the eight solvated diastereomeric salt pairs revealed that the type of hydrogen-bonding network (sheetlike or columnar) and the arrangement of the columnar structures were controlled by the length of the included alcohol. By comparison of the two diastereomeric MA salt crystal structures, their relative stability to display chirality switching was investigated.
- Kodama, Koichi,Shitara, Hiroaki,Hirose, Takuji
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- Chiral separation of D,L-mandelic acid through cellulose membranes
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This work reports the chiral separation of D,L-mandelic acid with cellulose membranes. Cellulose was chosen as membrane material because it possesses multichiral carbon atoms in its molecular structure unit. The flux and permselective properties of membra
- Ma, Chao,Xu, Xiao-Lin,Ai, Ping,Xie, Sheng-Ming,Lv, Ying-Chun,Shan, Hai-Qin,Yuan, Li-Ming
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- HYDRATION OF CYANOHYDRINS IN WEEKLY ALKALINE SOLUTIONS OF BORIC ACID SALTS
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α-Hydroxyamides and α-hydroxyacids were prepared in satisfactory yield by heating aldehyde-derived cyanohydrins in aqueous solution in the presence of borax or alkaline borates.
- Jammot, Jacqueline,Pascal, Robert,Commeyras, Auguste
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- Directed evolution of nitrilase PpL19 from Pseudomonas psychrotolerans L19 and identification of enantiocomplementary mutants toward mandelonitrile
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Nitrilase PpL19 from Pseudomonas psychrotolerans L19 can hydrolyze racemic mandelonitrile to (S)-mandelic acid with an enantiomeric excess (ee) value of 52.7%. In this study, random mutagenesis combined with site-directed mutagenesis was performed to iden
- Sun, Huihui,Wang, Hualei,Gao, Wenyuan,Chen, Lifeng,Wu, Kai,Wei, Dongzhi
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- Stabilizing effects of cations on lipases depend on the immobilization protocol
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The effect of an additive on enzyme stability used to be considered an intrinsic feature of a lipase. However, in this paper we have found that the effect of additive on enzyme stability depends on the immobilization protocol. After assaying the effects of diverse chloride salts with different cations on different lipases activity, no relevant effect was detected. Free enzymes or the covalently immobilized enzymes are not stabilized by these cations for any of the studied lipases. However, Mn2+ and Ca2+ (at a concentration of 5 mM) are able to greatly stabilize the lipases from Rhizomucor miehei (RML) and Candida rugosa (CRL) when they are present during the inactivation, but only if the enzymes are immobilized on octyl-agarose (stabilization factor ranging from 20 to 50). The effect was only detected when using more than 2.5 mM of the cations, and reached the maximum value at 5 mM, suggesting a saturation mechanism of action. The stabilization seemed to be based on a specific mechanism, and required the recognition sites to be saturated by the cations. Mg2+ has no effect on enzyme stability for both enzymes, but it is able to suppress the stabilization promoted by the other two cations using CRL; while it has no effect on the cation stabilization when using RML. This is the first report of a cation induced enzyme stabilization effect that depends on the lipase immobilization protocol.
- Fernandez-Lopez, Laura,Bartolome-Cabrero, Rocio,Rodriguez, Maria Daniela,Dos Santos, Cleiton S.,Rueda, Nazzoly,Fernandez-Lafuente, Roberto
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- (R)-mandelic acid (S)-alanine hemihydrate
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Crystals of the title complex, C3H7NO2·C8H8O 3·0.5H2O, were obtained from an aqueous solution containing racemic mandelic acid and (S)-alanine. The unit cell includes two independent molecular complexes and one water molecule. The structure formed by (R)-mandelic acid and (S)-alanine in a 1:1 molar ratio shows the successful optical separation of racemic mandelic acid. Strong hydrogen bonding, with a rather short O...O separation of 2.494 (3) A, is observed between the carboxyl and carboxylate groups. A structural comparison suggests that the strong hydrogen bonding affects the neighbouring covalent bond.
- Hu, Zi-Qiang,Xu, Duan-Jun,Xu, Yuan-Zhi,Wu, Jing-Yun,Chiang, Michael Y.
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- Application of a recombinant Escherichia coli whole-cell catalyst expressing hydroxynitrile lyase and nitrilase activities in ionic liquids for the production of (S)-mandelic acid and (S)-mandeloamide
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The conversion of benzaldehyde and cyanide into mandelic acid and mandeloamide by a recombinant Escherichia coli strain which simultaneously expressed an (S)-hydroxynitrile lyase (oxynitrilase) from cassava (Manihot esculenta) and an aryl-acetonitrilase from Pseudomonas fluorescens EBC191 was studied. Benzaldehyde exhibited a pronounced inhibitory effect on the nitrilase activity in concentrations ≥25 mM. Therefore, it was tested if two-phase systems consisting of a buffered aqueous phase and the ionic liquid 1-butyl-1-pyrrolidinium bis(trifluoromethanesulfonyl)imide (BMpl NTf 2) or 1-butyl-3-methylimidazolium hexafluorophosphate (BMim PF 6) could be used for the intended biotransformation. The distribution coefficients of the substrates, intermediates and products of the reaction were determined and it was found that BMpl NTf2 and BMim PF6 were highly efficient as substrate reservoirs for benzaldehyde. The recombinant E. coli strain was active in the presence of BMpl NTf2 or BMim PF6 phases and converted benzaldehyde and cyanide into mandelic acid and mandeloamide. The two-phase systems allowed the conversion of benzaldehyde dissolved in the ionic liquids to a concentration of 700 mM with product yields (=sum of mandelic acid and mandeloamide) of 87-100%. The cells were slightly more effective in the presence of BMpl NTf2 than in the presence of BMim PF6. In both two-phase systems benzaldehyde and cyanide were converted into (S)-mandeloamide and (S)-mandelic acid with enantiomeric excesses ≥94%. The recombinant E. coli cells formed, in the two-phase systems with ionic liquids and increased substrate concentrations, higher relative amounts of mandelo-amide than in a purely aqueous system with lower substrate concentrations.
- Baum, Stefanie,Van Rantwijk, Fred,Stolz, Andreas
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- Coenzyme Models. 25. Facile Oxidation of Hemithiol Acetals by Flavin. Supporting Evidence for the Enediol Mechanism of Glyoxalase I
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The rearrangement of hemithiol acetals (1) to α-hydroxythiol esters (2) was inhibited almost completely on the addition of 3-methyltetra-O-acetylriboflavin (MeFl), and corresponding α-keto acids were produced in good yields.Since (i) flavin is able to tra
- Shinkai, Seiji,Yamashita, Takaharu,Kusano, Yumiko,Manabe, Osamu
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- Optical resolution and mechanism using enantioselective cellulose, sodium alginate and hydroxypropyl-β-cyclodextrin membranes
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Chiral solid membranes of cellulose, sodium alginate, and hydroxypropyl-β-cyclodextrin were prepared for chiral dialysis separations. After optimizing the membrane material concentrations, the membrane preparation conditions and the feed concentrations, enantiomeric excesses of 89.1%, 42.6%, and 59.1% were obtained for mandelic acid on the cellulose membrane, p-hydroxy phenylglycine on the sodium alginate membrane, and p-hydroxy phenylglycine on the hydroxypropyl-β-cyclodextrin membrane, respectively. To study the optical resolution mechanism, chiral discrimination by membrane adsorption, solid phase extraction, membrane chromatography, high-pressure liquid chromatography ultrafiltration were performed. All of the experimental results showed that the first adsorbed enantiomer was not the enantiomer that first permeated the membrane. The crystal structures of mandelic acid and p-hydroxy phenylglycine are the racematic compounds. We suggest that the chiral separation mechanism of the solid membrane is “adsorption – association – diffusion,” which is able to explain the optical resolution of the enantioselective membrane. This is also the first report in which solid membranes of sodium alginate and hydroxypropyl-β-cyclodextrin were used in the chiral separation of p-hydroxy phenylglycine.
- Yuan, Li-Ming,Ma, Wei,Xu, Mei,Zhao, Hui-Lin,Li, Yuan-Yuan,Wang, Rui-Lin,Duan, Ai-Hong,Ai, Ping,Chen, Xue-Xian
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- Modulation of the enantioselectivity of Candida antarctica B lipase via conformational engineering: Kinetic resolution of (±)-α-hydroxy-phenylacetic acid derivatives
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The modulation, via immobilization and engineering the reaction medium, of the enantioselectivity exhibited by the lipase from Candida antarctica B (CABL) in the hydrolysis of α-hydroxy-phenylacetic acid derivatives is shown. The enzyme was purified and immobilized using different protocols to obtain immobilized enzyme preparations with different orientations and micro-environments. The catalytic properties (activity, specificity, enantioselectivity) of the resulting derivatives were found to be quite different from each other. The enantioselectivity (E value) strongly depends on the type of derivative and the conditions employed. Thus, the enzyme immobilized on cyanogen bromide (CNBr) presented E=7.4, while the PEI derivative yielded E=67 in the hydrolysis of α-hydroxy-phenylacetic acid methyl ester under similar conditions. Moreover, the enantioselectivity of the PEI derivative decreased from 67 to 14 on lowering the reaction temperature from 25 to 4°C at pH 5, while the E of some other derivatives improved significantly under similar experimental changes. Similar changes in the E values were observed in the hydrolysis of (RS)-2-butyroyl-2-phenylacetic acid. Using this substrate, the interfacially adsorbed enzyme (octadecyl) afforded an E value of only 2 at pH 5, while the glutaraldehyde derivative presented a high enantioselectivity (E >400) under all conditions studied. The corresponding (S)-ester and (R)-acid were obtained with excellent enantiomeric excess using the glutaraldehyde derivative, while using the interfacially immobilized one there was no appreciable enantioselectivity. Thus, using differently immobilized derivatives and different experimental conditions, lipase enantioselectivity could vary from negligible to up to 400. The experimental conditions were also found to have varying effects on the different lipase derivatives.
- Palomo, Jose M,Fernandez-Lorente, Gloria,Mateo, Cesar,Fuentes, Manuel,Fernandez-Lafuente, Roberto,Guisan, Jose M
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- Efficient and selective oxidation of primary and secondary alcohols using an iron(III)/phenanthroline complex: Structural studies and catalytic activity
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An efficient catalytic system for the oxidation of alcohols has been developed by using iron(III) catalyst [Fe(phen)2Cl 2]NO3 (1) (phen = 1,10-phenanthroline) and H 2O2 as terminal oxidant. A series of primary and secondary alcohols were oxidized into aldehydes and ketones in good yields and excellent selectivities after a short reaction time. The mononuclear iron(III) complex [Fe(phen)2Cl2]NO3 was characterized by several independent methods. The X-ray structure shows distorted octahedral geometry around the FeIII center, which is in a high-spin state (S = 5/2) according to Moessbauer study. Copyright
- Biswas, Bhaskar,Kole, Niranjan,Al-Hunaiti, Afnan,Raeisaenen, Minna T.,Ansalone, Simone,Leskelae, Markku,Repo, Timo,Chen, Yen-Tung,Tsai, Hui-Lien,Naik, Anil D.,Railliet, Antoine P.,Garcia, Yann,Ghosh, Rajarshi
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- Discovery of a diverse set of esterases from hot spring microbial mat and sea sediment metagenomes
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Esterases are an important group of biocatalysts for synthetic organic chemistry. Functional metagenomics allows discovery of novel biocatalysts by providing access to the gene pool of the microbial community of a habitat. Two metagenomic libraries representing the gene pool of sea sediment and hot spring microbial mat were constructed. Functional screening of these libraries resulted in the isolation of total 8 clones with tributyrin hydrolytic activity. Sequence analysis revealed 10 putative lipolytic proteins with 42–99% homology to the protein sequences in the databases, nine of which represented six known esterase families. Four of the encoded proteins represented Family V and amongst others, one each represented the Family VIII, pectin acetylesterase, enterobactin esterase, G-D-S-L family and OsmC domain containing esterase. One unusual lipolytic protein possessed poly-(3-hydroxybutyrate) depolymerase domain fused to lipase/esterase domain. Two phylogenetically related esterases (MLC3 and SLC5) belonging to family V were expressed and purified to homogeneity. The enzymes exhibited environment-adapted temperature optimum and thermostability. MLC3 was able to stereoselectively hydrolyze R-methyl mandelate to produce R-mandelic acid, an important chiral building block, which suggests MLC3 has potential commercial application.
- Ranjan, Ravi,Yadav, Manish Kumar,Suneja, Garima,Sharma, Rakesh
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- Thiamine Diphosphate Dependent KdcA-Catalysed Formyl Elongation of Aldehydes
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The formose reaction, one of the oldest name reactions in organic chemistry, uses formaldehyde as a C1 unit resulting in different monosaccharides and sugar-like compounds. Nucleophilic formyl elongation is an attractive option to obtain 1,2-fu
- Germer, Philipp,Gauchenova, Ekaterina,Walter, Lydia,Müller, Michael
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- A Four-Step Enzymatic Cascade for Efficient Production of L-Phenylglycine from Biobased L-Phenylalanine
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Enantiopure amino acids are of particular interest in the agrochemical and pharmaceutical industries. Here, we report a multi-enzyme cascade for efficient production of L-phenylglycine (L-Phg) from biobased L-phenylalanine (L-Phe). We first attempted to engineer Escherichia coli for expressing L-amino acid deaminase (LAAD) from Proteus mirabilis, hydroxymandelate synthase (HmaS) from Amycolatopsis orientalis, (S)-mandelate dehydrogenase (SMDH) from Pseudomonas putida, the endogenous aminotransferase (AT) encoded by ilvE and L-glutamate dehydrogenase (GluDH) from E. coli. However, 10 mM L-Phe only afforded the synthesis of 7.21±0.15 mM L-Phg. The accumulation of benzoylformic acid suggested that the transamination step might be rate-limiting. We next used leucine dehydrogenase (LeuDH) from Bacillus cereus to bypass the use of L-glutamate as amine donor, and 40 mM L-Phe gave 39.97±3.84 mM (6.04±0.58 g/L) L-Phg, reaching 99.9 % conversion. In summary, this work demonstrates a concise four-step enzymatic cascade for L-Phg synthesis from biobased L-Phe, with a potential for future industrial applications.
- Yuan, Jifeng,Zhu, Yuling
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- Method for synthesizing mandelic acid
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The invention relates to the technical field of compound preparation, and provides a method for synthesizing mandelic acid, which comprises the following steps: by using styrene as a basic raw material, trichloroisocyanuric acid as a chlorinating agent an
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Paragraph 0032; 0034-0035; 0037-0038; 0040-0041; 0043
(2021/02/06)
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- High-yield DL-mandelic acid synthesis process
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The invention provides a high-yield DL-mandelic acid synthesis process. The synthesis process specifically comprises the following steps: 1, treating benzaldehyde by using sodium hydrogen sulfite to obtain benzaldehyde sodium hydrogen sulfite; 2, extracting the benzaldehyde sodium hydrogen sulfite by using an organic solvent, recovering unreacted benzaldehyde in the benzaldehyde sodium hydrogen sulfite, and adding sodium cyanide after the extraction is completed to prepare mandelonitrile; 3, adding an inorganic acid, and then carrying out heating and pressure maintaining treatment to hydrolyze the mandelonitrile so as to obtain mandelic acid; and 4, purifying the mandelic acid. According to the method, the step of extracting the p-benzaldehyde sodium hydrogen sulfite salt is added, so that the probability that the product purity is reduced due to benzoin condensation is reduced, the recycled benzaldehyde can be returned to the raw material for use, and the yield can be increased in multiple rounds of reactions; and the hydrolysis process of the mandelonitrile adopts heating and pressure maintaining treatment, so that consumption of inorganic acid can be reduced, and the hydrolysis efficiency is improved.
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- Synthesis of α-hydroxycarboxylic acids from various aldehydes and ketones by direct electrocarboxylation: A facile, efficient and atom economy protocol
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In present work, the formation of α-hydroxycarboxylic acids have been described from various aromatic aldehydes and ketones via direct electrocarboxylation method with 80-92% of yield without any side product and can be purified by simple recrystallization using sacrificial Mg anode and Pt cathode in an undivided cell, CO2at (1 atm) was continuously bubbled in the cell throughout the reaction using tetrapropylammonium chloride as a supporting electrolyte in acetonitrile. The synthesized compounds obtained in fair to excellent yield with a high level of purity. The characterization of electrocarboxylated compounds was done with spectroscopic techniques like IR, NMR (1H & 13C), mass and elemental analysis.
- Singh, Kishanpal,Sohal, Harvinder Singh,Singh, Baljit
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p. 839 - 845
(2021/04/09)
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- Scrutinizing ligand exchange reactions in the formation of the precious group metal-organic framework RuII,II-HKUST-1: The impact of diruthenium tetracarboxylate precursor and modulator choice
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The precious group metal (PGM) analogues of the iconic metal-organic framework [Cu3(BTC)2] (HKUST-1; BTC = 1,3,5 benzenetricarboxylate) still represent a synthetic challenge, especially if targeting the univalent and ideally defect-free RuII,IIvariant. Herein we present a systematic study employing the controlled secondary building unit approach (CSA) by using a variety of diruthenium tetracarboxylate complexes [Ru2(RCO2)4] as precursors in the synthesis of univalent Ru-HKUST-1 samples. Carboxylate ligand exchange test reactions suggest the importance of a pKamatch between precursor ligand and BTC linker. For example,l-mandelate substituted precursors resulted in the most “perfect” samples of the investigated series with a fourfold increase in crystalline domain sizes compared to the established acetate route (according to PXRD and HR-TEM), high compositional purity (FT-IR, Raman, TGA and elemental analysis) and feature a so far unprecedentedly high BET surface area of 1789 m2g?1with the expected pore size distribution and total pore volume all similar to the ideal HKUST-1 parent structure.
- Heinz, Werner R.,Staude, Dominik,Mayer, David,Bunzen, Hana,Fischer, Roland A.
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supporting information
p. 5226 - 5235
(2021/04/26)
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- Enantioseparation of mandelic acid on vancomycin column: Experimental and docking study
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So far, no detailed view has been expressed regarding the interactions between vancomycin and racemic compounds including mandelic acid. In the current study, a chiral stationary phase was prepared by using 3-aminopropyltriethoxysilane and succinic anhydride to graft carboxylated silica microspheres and subsequently by activating the carboxylic acid group for vancomycin immobilization. Characterization by elemental analysis, Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance, and thermogravimetric analysis demonstrated effective functionalization of the silica surface. R and S enantiomers of mandelic acid were separated by the synthetic vancomycin column. Finally, the interaction between vancomycin and R/S mandelic acid enantiomers was simulated by Auto-dock Vina. The binding energies of interactions between R and S enantiomers and vancomycin chiral stationary phase were different. In the most probable interaction, the difference in mandelic acid binding energy was approximately 0.2 kcal/mol. In addition, circular dichroism spectra of vancomycin interacting with R and S enantiomers showed different patterns. Therefore, R and S mandelic acid enantiomers may occupy various binding pockets and interact with different vancomycin functions. These observations emphasized the different retention of R and S mandelic acid enantiomers in vancomycin chiral column.
- Shahnani, Mostafa,Sefidbakht, Yahya,Maghari, Shokoofeh,Mehdi, Ahmad,Rezadoost, Hassan,Ghassempour, Alireza
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supporting information
p. 1289 - 1298
(2020/08/19)
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- Expanding the repertoire of nitrilases with broad substrate specificity and high substrate tolerance for biocatalytic applications
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Enzymatic conversion of nitriles to carboxylic acids by nitrilases has gained significance in the green synthesis of several pharmaceutical precursors and fine chemicals. Although nitrilases from several sources have been characterized, there exists a scope for identifying broad spectrum nitrilases exhibiting higher substrate tolerance and better thermostability to develop industrially relevant biocatalytic processes. Through genome mining, we have identified nine novel nitrilase sequences from bacteria and evaluated their activity on a broad spectrum of 23 industrially relevant nitrile substrates. Nitrilases from Zobellia galactanivorans, Achromobacter insolitus and Cupriavidus necator were highly active on varying classes of nitriles and applied as whole cell biocatalysts in lab scale processes. Z. galactanivorans nitrilase could convert 4-cyanopyridine to achieve yields of 1.79 M isonicotinic acid within 3 h via fed-batch substrate addition. The nitrilase from A. insolitus could hydrolyze 630 mM iminodiacetonitrile at a fast rate, effecting 86 % conversion to iminodiacetic acid within 1 h. The arylaliphatic nitrilase from C. necator catalysed enantioselective hydrolysis of 740 mM mandelonitrile to (R)-mandelic acid in 4 h. Significantly high product yields suggest that these enzymes would be promising additions to the suite of nitrilases for upscale biocatalytic application.
- Rayavarapu, Pratima,Shah, Shikha,Sunder, Avinash Vellore,Wangikar, Pramod P.
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p. 289 - 296
(2020/05/18)
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- In vivo cascade catalysis of aromatic amino acids to the respective mandelic acids using recombinant E. coli cells expressing hydroxymandelate synthase (HMS) from Amycolatopsis mediterranei
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Mandelic acids are valuable products which are used in a broad field of applications. The enzyme hydroxymandelate synthase (HMS) is a non-heme iron dioxygenase which converts para-hydroxyphenylpyruvate and other 3-aryl pyruvates by decarboxylation to the corresponding mandelates. In the present work, the gene hms encoding the hydroxymandelate synthase from Amycolatopsis mediterranei was cloned and overexpressed in Escherichia coli BL21(DE3) for in vivo cascade catalysis taking advantage of resident aromatic amino acid transaminases. The resulting recombinant cells were used for whole cell biotransformations. We successfully accomplished the production of para-hydroxymandelate exclusively by using the aromatic amino acid L-tyrosine in biotransformation. Furthermore, by utilizing different phenylalanine derivatives (including chloro-, fluoro- and hydroxylated amino acids), the corresponding S-mandelic acids were obtained with high conversion (21–87 %) and high ee (38–97%). This process is an alternative and attractive way to get access to a variety of mandelic acids.
- Youn, Jung-Won,Albermann, Christoph,Sprenger, Georg A.
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- One-Pot Cascade Biotransformation for Efficient Synthesis of Benzyl Alcohol and Its Analogs
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Benzyl alcohol is a naturally occurring aromatic alcohol and has been widely used in the cosmetics and flavor/fragrance industries. The whole-cell biotransformation for synthesis of benzyl alcohol directly from bio-based L-phenylalanine (L-Phe) was herein explored using an artificial enzyme cascade in Escherichia coli. Benzaldehyde was first produced from L-Phe via four heterologous enzymatic steps that comprises L-amino acid deaminase (LAAD), hydroxymandelate synthase (HmaS), (S)-mandelate dehydrogenase (SMDH) and benzoylformate decarboxylase (BFD). The subsequent reduction of benzaldehyde to benzyl alcohol was achieved by a broad substrate specificity phenylacetaldehyde reductase (PAR) from Solanum lycopersicum. We found the designed enzyme cascade could efficiently convert L-Phe into benzyl alcohol with conversion above 99%. In addition, we also examined L-tyrosine (L-Tyr) and m-fluoro-phenylalanine (m-f-Phe) as substrates, the cascade biotransformation could also efficiently produce p-hydroxybenzyl alcohol and m-fluoro-benzyl alcohol. In summary, the developed biocatalytic pathway has great potential to produce various high-valued fine chemicals.
- Liu, Lijun,Zhu, Yuling,Chen, Yufen,Chen, Huiyu,Fan, Cong,Mo, Qiwen,Yuan, Jifeng
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supporting information
p. 1018 - 1021
(2020/03/04)
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- Oxalyl-CoA Decarboxylase Enables Nucleophilic One-Carbon Extension of Aldehydes to Chiral α-Hydroxy Acids
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The synthesis of complex molecules from simple, renewable carbon units is the goal of a sustainable economy. Here we explored the biocatalytic potential of the thiamine-diphosphate-dependent (ThDP) oxalyl-CoA decarboxylase (OXC)/2-hydroxyacyl-CoA lyase (HACL) superfamily that naturally catalyzes the shortening of acyl-CoA thioester substrates through the release of the C1-unit formyl-CoA. We show that the OXC/HACL superfamily contains promiscuous members that can be reversed to perform nucleophilic C1-extensions of various aldehydes to yield the corresponding 2-hydroxyacyl-CoA thioesters. We improved the catalytic properties of Methylorubrum extorquens OXC by rational enzyme engineering and combined it with two newly described enzymes—a specific oxalyl-CoA synthetase and a 2-hydroxyacyl-CoA thioesterase. This enzymatic cascade enabled continuous conversion of oxalate and aromatic aldehydes into valuable (S)-α-hydroxy acids with enantiomeric excess up to 99 %.
- Burgener, Simon,Cortina, Ni?a Socorro,Erb, Tobias J.
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supporting information
p. 5526 - 5530
(2020/02/20)
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- An Enantioconvergent Benzylic Hydroxylation Using a Chiral Aryl Iodide in a Dual Activation Mode
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The application of a triazole-substituted chiral iodoarene in a direct enantioselective hydroxylation of alkyl arenes is reported. This method allows the rapid synthesis of chiral benzyl alcohols in high yields and stereocontrol, despite its nontemplated nature. In a cascade activation consisting of an initial irradiation-induced radical C-H-bromination and a consecutive enantioconvergent hydroxylation, the iodoarene catalyst has a dual role. It initiates the radical bromination in its oxidized state through an in-situ-formed bromoiodane and in the second, Cu-catalyzed step, it acts as a chiral ligand. This work demonstrates the ability of a chiral aryl iodide catalyst acting both as an oxidant and as a chiral ligand in a highly enantioselective C-H-activating transformation. Furthermore, this concept presents an enantioconvergent hydroxylation with high selectivity using a synthetic catalyst.
- Abazid, Ayham H.,Clamor, Nils,Nachtsheim, Boris J.
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p. 8042 - 8048
(2020/09/21)
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- Preparation of α-hydroxyphenylacetic acid with cyclodextrins as an effective phase-transfer catalyst and its reaction mechanism
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An effective procedure for the synthesis of α-hydroxyphenylacetic acid with cyclodextrin (CD) catalysts was developed. The phase-transfer catalyst types, catalyst loadings, reaction times, reaction temperatures, and substrate molar ratios were investigated to optimize the reaction conditions. In addition, the factors that affect the reaction were studied, and the relationship between benzaldehyde and β-cyclodextrin (β-CD) was analyzed through 2D-ROESY. The equilibrium constant when β-CD was used as the catalyst was calculated. The results indicated that β-CD is the optimal catalyst for the reported reaction (yield: 69.08%). Furthermore, the mechanism underlying the reported reaction was proposed.
- Tian, Bing Ren,Zhang, Rui Xia,Chu, Hui Min,Huang, Qing,Wang, Zhi Zhong
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p. 359 - 368
(2019/05/16)
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- Three-Component Synthesis of Isoquinoline Derivatives by a Relay Catalysis with a Single Rhodium(III) Catalyst
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A rhodium(III)-catalyzed one-pot three-component reaction of N-methoxybenzamide, α-diazoester, and alkyne was developed, providing an alternative way to synthesize isoquinoline derivatives. Mechanistically, it is a relay catalysis, and the reaction occurred via successive O-alkylation and C-H activation processes, both of which were promoted by the same catalyst.
- Zhou, Chao,Jiang, Jijun,Wang, Jun
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supporting information
p. 4971 - 4975
(2019/09/03)
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- Method for preparing pregabalin by adopting ion exchange method
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The present invention belongs to the technical field of preparation of compounds, and relates to a method for preparing pregabalin by using an ion exchange method. The method comprises: (1) S,S-salt dissociation: in the presence of a solvent, carrying out dissociation on a S,S salt through an anion exchange resin to obtain a pregabalin solution; and (2) pregabalin preparation: concentrating the obtained pregabalin solution, adding a first organic solvent, and crystallizing to obtain pregabalin. According to the present invention, the method has advantages of high product purity, high yield, low mandelic acid residue, less ash content, environmental protection, easy operation, economy and the like.
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Paragraph 0033; 0036-0037; 0039; 0042-0043; 0046; 0049- 0064
(2019/08/21)
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- Preparation method of mandelic acid
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The invention discloses a preparation method of mandelic acid. Benzaldehyde and Benzyltriethylammonium chloride are added into a trichloromethane solvent, a certain concentration of liquid alkali is dripped at a certain temperature, after the liquid alkal
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Paragraph 0018-0057
(2019/01/07)
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- Enantioseparation of chiral mandelic acid derivatives by supercritical fluid chromatography
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Mandelic acid and its derivatives are important chiral analogs which are widely used in the pharmaceutical synthetic industry. The present study investigated the enantiomeric separation of six mandelic acids (mandelic acid, 2-chloromandelic acid, 3-chloromandelic acid, 4-chloromandelic acid, 4-bromomandelic acid, 4-methoxymandelic acid) on the Chiralpak AD-3 column by supercritical fluid chromatography. The influences of volume fraction of trifluoroacetic acid, type and percentage of modifier, column temperature, and backpressure on the separation efficiency were investigated. And the enantiomer elution order was determined. The results show that, for a given modifier, the retention factor, the separation factor, and the separation resolution decreased gradually with increasing the volume ratio of the modifier. At the same volume ratio of modifier, the retention factor of the mandelic acid and its derivatives increased in the order of methanol, ethanol, and isopropanol, except 3-chloromandelic acid. The separation factor and the separation resolution decreased with the increase of column temperature (below the temperature limit). The backpressure affected the enantioseparation process: As the backpressure increased, a corresponding decrease in retention factor was observed. Under the same chiral column conditions, the SFC method exhibited faster and more efficient separation with better enantioselectivity than the HPLC method.
- Ding, Jiawei,Zhang, Ming,Dai, Huixue,Lin, Chunmian
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p. 1245 - 1256
(2018/09/25)
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- Preparation method of DL-mandelic acid
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A preparation method of DL-mandelic acid comprises: using benzaldehyde, chloroform and sodium hydroxide as materials and beta-cyclodextrin as a catalyst, including the cyclodextrin via hydrophobic cavity structure that the beta-cyclodextrin has, forming d
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Paragraph 0012-0017
(2018/04/02)
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- Characterization of a new nitrilase from Hoeflea phototrophica DFL-43 for a two-step one-pot synthesis of (S)-β-amino acids
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A nitrilase from Hoeflea phototrophica DFL-43 (HpN) demonstrating excellent catalytic activity towards benzoylacetonitrile was identified from a nitrilase tool-box, which was developed previously in our laboratory for (R)-o-chloromandelic acid synthesis from o-chloromandelonitrile. The HpN was overexpressed in Escherichia coli BL21 (DE3), purified to homogeneity by nickel column affinity chromatography, and its biochemical properties were studied. The HpN was very stable at 30–40?°C, and highly active over a wide range of pH values (pH 6.0–10.0). In addition, the HpN could tolerate against several hydrophilic organic solvents. Steady-state kinetics indicated that HpN was highly active towards benzoylacetonitrile, giving a KM of 4.2?mM and a kcat of 170?s?1, the latter of which is ca. fivefold higher than the highest record reported so far. A cascade reaction for the synthesis of optically pure (S)-β-phenylalanine from benzoylacetonitrile was developed by coupling HpN with an ω-transaminase from Polaromonas sp. JS666 in toluene-water biphasic reaction system using β-alanine as an amino donor. Various (S)-β-amino acids could be produced from benzoylacetonitrile derivatives with moderate to high conversions (73–99%) and excellent enantioselectivity (> 99% ee). These results are significantly advantageous over previous studies, indicating a great potential of this cascade reaction for the practical synthesis of (S)-β-phenylalanine in the future.
- Zhang, Zhi-Jun,Cai, Rui-Feng,Xu, Jian-He
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p. 6047 - 6056
(2018/05/15)
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- Mild and versatile potassium fluoride/tetrabutylammonium fluoride protocol for ester hydrolysis
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A mild and versatile protocol of potassium fluoride/tetrabutylammonium fluoride (KF/TBAF) in aqueous tetrahydrofuran for ester hydrolysis has been developed. The method is applied on variety of aliphatic and aromatic ester moieties bearing acid or base sensitive functional groups. The conditions have been also applied on acetates to yield alcohols. The chirality of optically pure esters remained intact with the conditions of the reaction.
- Vijayalakshmi,Balakrishna,Mustafa, Shaik
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p. 309 - 311
(2018/01/11)
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- Reductive carboxylation of aromatic esters by electron transfer from magnesium metal
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Magnesium-promoted reductive carboxylation of ethyl benzoate in the presence of chlorotrimethylsilane in N,N-dimethylformamide brought about a new carbon-carbon bond formation between the carbonyl carbon atom and carbon dioxide to give the corresponding benzoylformic acid in good yield. It is noteworthy that only ethyl benzoates with substituents at the meta-position were converted into benzoylformic acid derivatives. Moreover, no mandelic acid was detected even under the reductive conditions. This result indicates that benzoylformic acid was obtained after hydrolysis of a carboxylated intermediate, which would be alive as a stabilized structure in the reaction media.
- Maekawa, Hirofumi,Okawara, Hikaru,Murakami, Taro
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p. 206 - 209
(2016/12/28)
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- The Synthesis of Chiral α-Aryl α-Hydroxy Carboxylic Acids via RuPHOX-Ru Catalyzed Asymmetric Hydrogenation
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A ruthenocenyl phosphino-oxazoline-ruthenium complex (RuPHOX?Ru) catalyzed asymmetric hydrogenation of α-aryl keto acids has been successfully developed, affording the corresponding chiral α-aryl α-hydroxy carboxylic acids in high yields and with up to 97% ee. The reaction could be performed on a gram scale with a relatively low catalyst loading (up to 5000 S/C) and the resulting products can be transformed to several chiral building blocks, biologically active compounds and chiral drugs. (Figure presented.).
- Guo, Huan,Li, Jing,Liu, Delong,Zhang, Wanbin
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p. 3665 - 3673
(2017/09/11)
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- Chemoenzymatic Preparation of Enantiomerically Enriched (R)-(–)-Mandelic Acid Derivatives: Application in the Synthesis of the Active Agent Pemoline
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The enantioselective resolution of several racemic derivatives of mandelic acid methyl ester catalyzed by lipases from Pseudomonas fluorescens (Amano AK) or Burkholderia cepacia (Amano PS-C II and Amano PS-IM) has been achieved. A gram-scale lipase-mediated kinetic resolution approach has been developed that allows the facile synthesis of the corresponding methyl (R)-(–)-mandelates with excellent enantiomeric excesses (up to >99 % ee) and reaction enantioselectivity (E values up to >200). The dopaminergic agent pemoline, used in the treatment of attention-deficit hyperactivity disorder (ADHD) and narcolepsy, was synthesized with 98 % ee in a straightforward route by condensing the prepared methyl (R)-(–)-mandelate with guanidine hydrochloride under basic conditions. The desired (R)-(+)-pemoline in optically pure form (>99 % ee) was obtained after two recrystallizations from ethanol. However, it was confirmed by chiral HPLC that optically active pemoline undergoes racemization in methanol solution.
- Potera?a, Marcin,Dranka, Maciej,Borowiecki, Pawe?
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p. 2290 - 2304
(2017/05/01)
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- One-Pot Enantioselective Synthesis of d-Phenylglycines from Racemic Mandelic Acids, Styrenes, or Biobased l-Phenylalanine via Cascade Biocatalysis
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Enantiopure d-phenylglycine and its derivatives are an important group of chiral amino acids with broad applications in thepharmaceutical industry. However, the existing synthetic methods for d-phenylglycine mainly rely on toxic cyanide chemistry and multistep processes. To provide green and safe alternatives, we envisaged cascade biocatalysis for the one-pot synthesis of d-phenylglycine from racemic mandelic acid, styrene, and biobased l-phenylalanine, respectively. Recombinant Escherichia coli (LZ110) was engineered to coexpress four enzymes to catalyze a 3-step reaction in one pot, transforming mandelic acid (210 mM) to give enantiopure d-phenylglycine in 29.5 g L?1 (195 mM) with 93% conversion. Using the same whole-cell catalyst, twelve other d-phenylglycine derivatives were also produced from the corresponding mandelic acid derivatives in high conversion (58–94%) and very high ee (93–99%). E. coli (LZ116) expressing seven enzymes was constructed for the transformation of styrene to enantiopure d-phenylglycine in 80% conversion via a one-pot 6-step cascade biotransformation. Twelve substituted d-phenylglycines were also produced from the corresponding styrene derivatives in high conversion (45–90%) and very high ee (92–99%) via the same cascade reactions. A nine-enzymeexpressing E. coli (LZ143) was engineered to transform biobased l-phenylalanine to enantiopure d-phenylglycine in 83% conversion via a one-pot 8-step transformation. Preparative biotransformations were also demonstrated. The high-yielding synthetic methods use cheap and green reagents (ammonia, glucose, and/or oxygen), and E. coli whole-cell catalysts, thus providing green and useful alternative methods for manufacturing d-phenylglycine. (Figure presented.).
- Zhou, Yi,Wu, Shuke,Li, Zhi
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p. 4305 - 4316
(2017/11/21)
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- Method for preparing mandelic acid from styrene oxide
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The invention provides a method for preparing mandelic acid from styrene oxide. The preparation method comprises the following steps: preparing phenyl glycol from styrene oxide through hydration under the catalysis of a NY-series catalyst; and introducing air for selective oxidation of mandelic acid from phenyl glycol under the action of an active carbon-loaded Pd-Au catalyst. The preparation method is characterized in that raw materials are mainly composed of styrene oxide, the NY-series catalyst and the active carbon-loaded Pd-Au catalyst. The preparation method for mandelic acid uses cheap and easily available raw materials and is simple in process, mild in conditions and high in product yield and product purity.
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Paragraph 0041; 0044; 0047; 0050; 0053; 0056
(2017/10/07)
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- Asymmetric hydrogenation reaction of alpha-ketoacids compound
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The invention relates to the technical field of organic chemistry, especially to an asymmetric hydrogenation reaction of an alpha-ketoacids compound. The asymmetric hydrogenation reaction comprises a scheme shown in the description. In the scheme, R1 is phenyl, substituted phenyl, naphthyl, substituted naphthyl, C1-C6 alkyl, or aralkyl; a substituent group is C1-C6 alkyl, C1-C6 alkoxy, or halogen; and the number of the substituent group is 1-3. In the scheme, M is a chiral spiro-pyridylamino phosphine ligand iridium complex having a structure shown in the description. In the structure, R is hydrogen, 3-methyl, 4-tBu, or 6-methyl.
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Paragraph 0033; 0037
(2016/10/10)
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- Copper encapsulated alkaloids composite: An effective heterogeneous catalyst for electrocatalytic asymmetric hydrogenation
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A novel heterogeneous catalyst, alkaloid@Cu was prepared by the entrapment of commercially purchased alkaloids within non-noble metallic copper nanoparticles. This composite was compacted into a coin and directly used as cathode for electrocatalytic asymmetric hydrogenation of aromatic ketones. Using water as hydrogen source, optically active alcohols with 71% ee value and 93% yield were obtained under very mild conditions.
- Yang, Heng-Pan,Fen, Qiu,Wang, Huan,Lu, Jia-Xing
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- Enzymatic Resolution by a d-Lactate Oxidase Catalyzed Reaction for (S)-2-Hydroxycarboxylic Acids
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Oxidase-catalyzed kinetic resolution is important for the production of enantiopure 2-hydroxycarboxylic acids (2-HAs), which are versatile building blocks for the synthesis of many significant compounds. However, in contrast to that of (R)-2-HAs, the production of (S)-2-HA is challenging because of the lack of related oxidases. Herein, suitable enzymes were screened systematically through the analysis of numerous putative d-lactate oxidase sequences and identification of several required properties. Finally, a d-lactate oxidase from Gluconobacter oxydans 621H with advantageous characteristics, such as good solubility, broad substrate spectrum, and high stereoselectivity, was selected to resolve 2-HAs into (S)-2-HAs. A variety of (S)-2-HAs was produced successfully using this d-lactate oxidase with excellent enantiomeric excess values (>99 %). The presented screening criteria and approach for target biocatalysis suggested a guideline for the production of optically active chemicals such as (S)-2-HAs.
- Sheng, Binbin,Xu, Jing,Ge, Yongsheng,Zhang, Shuo,Wang, Danqi,Gao, Chao,Ma, Cuiqing,Xu, Ping
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p. 2630 - 2633
(2016/08/30)
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- Production Of Enantiopure alpha-Hydroxy Carboxylic Acids From Alkenes By Cascade Biocatalysis
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The invention provides compositions comprising an alkene epoxidase and a selective epoxide hydrolase, such as a recombinant microorganism comprising a first heterologous nucleic acid encoding an alkene epoxidase and a second heterologous nucleic acid encoding a selective epoxide hydrolase. Exemplary alkene epoxidases include StyAB, while exemplary selective epoxide hydrolases include epoxide hydrolases from Sphingomonas, Solanum tuberosum, or Aspergillus. The invention also provides non-toxic methods of making enantiomerically pure vicinal diols or enantiomerically pure alpha-hydroxy carboxylic acids using these compositions and microorganisms.
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Paragraph 0074-0076
(2016/05/02)
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- Easy stabilization of interfacially activated lipases using heterofunctional divinyl sulfone activated-octyl agarose beads. Modulation of the immobilized enzymes by altering their nanoenvironment
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Octyl-agarose is a support that permits the one step immobilization, stabilization and purification of lipases. However, the enzyme may be released from the support under drastic conditions. This paper describes a new heterofunctional support, octyl agarose beads activated with divinyl sulfone, that has proved to be useful to produce very stable and active biocatalysts of lipases from Candida rugosa (CRL), Rhizomucor miehei (RML) and Thermomyces lanuginosus (TLL), able to work under any reaction conditions without risking enzyme desorption. The three enzymes failed in immobilization on glyoxyl-octyl supports for different reasons. The immobilization at pH 5 permitted to keep the good properties of octyl agarose. Further incubation at pH 8 permitted to establish at least one covalent enzyme-support bond per enzyme molecule (preventing the risk of enzyme desorption), avoiding the inactivation produced at pH 10, and the final result is that all three new biocatalysts are more active than the octyl-glyoxyl counterparts and much more stable (e.g.; 20 using CRL). The end of the enzyme-support reaction was achieved via blocking the vinylsulfone groups with different nucleophiles (cationic, anionic, hydrophobic, etc). This not only determined the final enzyme stability, but also the activity, selectivity and even specificity of the different immobilized preparations.
- Albuquerque, Tiago L.De,Rueda, Nazzoly,Dos Santos, Jose C.S.,Barbosa, Oveimar,Ortiz, Claudia,Binay, Baris,?zdemir, Ece,Gon?alves, Luciana R.B.,Fernandez-Lafuente, Roberto
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p. 865 - 874
(2016/06/09)
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- Aerobic alcohol oxidation and oxygen atom transfer reactions catalyzed by a nonheme iron(II)-α-keto acid complex
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α-Ketoglutarate-dependent enzymes catalyze many important biological oxidation/oxygenation reactions. Iron(iv)-oxo intermediates have been established as key oxidants in these oxidation reactions. While most reported model iron(ii)-α-keto acid complexes exhibit stoichiometric reactivity, selective oxidation of substrates with dioxygen catalyzed by biomimetic iron(ii)-α-keto acid complexes remains unexplored. In this direction, we have investigated the ability of an iron(ii) complex [(TpPh,Me)FeII(BF)] (1) (TpPh,Me = hydrotris(3-phenyl-5-methylpyrazolyl)borate and BF = monoanionic benzoylformate) to catalyze the aerobic oxidation of organic substrates. An iron-oxo oxidant, intercepted in the reaction of 1 with O2, selectively oxidizes sulfides to sulfoxides, alkenes to epoxides, and alcohols to the corresponding carbonyl compounds. The oxidant from 1 is able to hydroxylate the benzylic carbon of phenylacetic acid to afford mandelic acid with the incorporation of one oxygen atom from O2 into the product. The iron(ii)-benzoylformate complex oxidatively converts phenoxyacetic acids to the corresponding phenols, thereby mimicking the function of iron(ii)-α-ketoglutarate-dependent 2,4-dichlorophenoxyacetate dioxygenase (TfdA). Furthermore, complex 1 exhibits catalytic aerobic oxidation of alcohols and oxygen atom transfer reactions with multiple turnovers.
- Sheet, Debobrata,Paine, Tapan Kanti
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p. 5322 - 5331
(2016/08/02)
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- Cascade Biocatalysis for Sustainable Asymmetric Synthesis: From Biobased l-Phenylalanine to High-Value Chiral Chemicals
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Sustainable synthesis of useful and valuable chiral fine chemicals from renewable feedstocks is highly desirable but remains challenging. Reported herein is a designed and engineered set of unique non-natural biocatalytic cascades to achieve the asymmetric synthesis of chiral epoxide, diols, hydroxy acid, and amino acid in high yield and with excellent ee values from the easily available biobased l-phenylalanine. Each of the cascades was efficiently performed in one pot by using the cells of a single recombinant strain over-expressing 4–10 different enzymes. The cascade biocatalysis approach is promising for upgrading biobased bulk chemicals to high-value chiral chemicals. In addition, combining the non-natural enzyme cascades with the natural metabolic pathway of the host strain enabled the fermentative production of the chiral fine chemicals from glucose.
- Zhou, Yi,Wu, Shuke,Li, Zhi
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supporting information
p. 11647 - 11650
(2016/11/17)
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- Improved performance of lipases immobilized on heterofunctional octyl-glyoxyl agarose beads
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A new heterofunctional support, octyl-glyoxyl agarose, is proposed in this study. The supports were prepared by simple periodate oxidation of the commercial octyl-agarose, introducing 25 μmol of glyoxyl groups per wet gram of support. This support was assayed with three different lipases (those from Candida antarctica (form B), Thermomyces lanuginosus (TLL) or Rhizomucor miehei) and the artificial phospholipase Lecitase Ultra. Used at pH 7, the new support maintained as first immobilization step the lipase interfacial activation. Thus, it was possible to have the purification and immobilization of the enzyme in one step. Moreover, stabilization of the open form of the lipase was achieved. The covalent enzyme/support bonds cannot be obtained if the immobilized enzyme was not incubated at alkaline pH value. This incubation at pH 10 of the previously immobilized enzymes produced a smaller decrease in enzyme activity when compared to the direct immobilization of the enzymes on glyoxyl-agarose at pH 10, because the immobilization via interfacial activation promoted a stabilization of the lipases. Except in the case of TLL (covalent attachment involved 70% of the enzyme molecules), covalent immobilization yield was over 80%. The non-covalent attached enzyme molecules were discarded by washings with detergent solutions and the new biocatalysts were compared to the octyl-agarose immobilized enzymes. While the stability in thermal and organic solvents inactivations was increased for Lecitase Ultra, CALB and RML, TLL improved its stability in organic media but its thermal stability decreased after covalent attachment of the interfacially activated enzyme. This stabilization resulted in octyl-glyoxyl-lipase preparations which presented higher activity in the presence of organic solvents. Finally, while octyl-agarose released enzyme molecules after incubation at high temperatures or in the presence of organic solvents and detergents, the covalently immobilized enzyme remained attached to the support even after boiling the enzyme in SDS, eliminating the risks of product contamination.
- Rueda, Nazzoly,Dos Santos, Jose C. S.,Torres, Rodrigo,Ortiz, Claudia,Barbosa, Oveimar,Fernandez-Lafuente, Roberto
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p. 11212 - 11222
(2015/02/05)
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- Solid phase behavior in the chiral systems of various 2-hydroxy-2-phenylacetic acid (mandelic acid) derivatives
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The solid phase behavior of a series of monosubstituted F-, Cl-, Br-, I-, and CH3- and two 2,4-halogen-disubstituted 2-hydroxy-2-phenylacetic acid (mandelic acid) derivatives was investigated. The study includes detailed information about melting temperature, melting enthalpy, X-ray diffraction data, as well as selected binary phase diagrams of the respective chiral systems. Aside from the known metastable conglomerate 2-chloromandelic acid, evidence for two more metastable conglomerates was found.
- Von Langermann, Jan,Temmel, Erik,Seidel-Morgenstern, Andreas,Lorenz, Heike
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p. 721 - 728
(2015/03/30)
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- Alkaloid-induced asymmetric hydrogenation on a Cu nanoparticle cathode by electrochemical conditions
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Copper nanoparticles were prepared in an aqueous solution, compacted into a coin, and used as a cathode for asymmetric hydrogenation by the electrochemical method for the first time. A good ee value and excellent yield were obtained under mild conditions. Electrochemical conditions were crucial for alkaloid adsorption on metallic Cu, which is a key process of asymmetric induction. Furthermore, the ee value was linear with an adsorption amount.
- Yang, Heng-Pan,Wang, Huan,Lu, Jia-Xing
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- Non-linear effects in the enantiomeric separation of mandelic acid using the mixtures of amphoteric resolving agents
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Abstract In this study, (S)-phenylalanine, aspartame and (S)-pregabalin, which contain α-, β- and γ-amino acidic moieties were successfully applied as resolving agents for the enantiomeric separation of mandelic acid via the formation of diastereomeric salts. The resolution of mandelic acid was also attempted with mixtures of the corresponding resolving agents and a more efficient enantiomeric separation of the mandelic acid was observed compared with the given sole resolving agents in a few instances. The best results were obtained with a mixture of (S)-phenylalanine and (S)-alanine; the latter resolving agent was insufficient when it was applied alone. The resolution efficiency of mandelic acid could also be improved by applying structurally related amphoteric achiral additives along with the corresponding resolving agents.
- Szeleczky, Zsolt,Bagi, Péter,Fodi, Balázs,Semsey, Sándor,Pálovics, Emese,Faigl, Ferenc,Fogassy, Elemér
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p. 721 - 731
(2015/07/15)
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- Synthesis of tertiary and quaternary amine derivatives from wood resin as chiral NMR solvating agents
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Chiral tertiary and quaternary amine solvating agents for NMR spectroscopy were synthesized from the wood resin derivative (+)-dehydroabietylamine (2). The resolution of enantiomers of model compounds [Mosher's acid (3) and its n-Bu4N salt (4)] (guests) by (+)-dehydroabietyl-N,N-dimethylmethanamine (5) and its ten different ammonium salts (hosts) was studied. The best results with 3 were obtained using 5 while with 4 the best enantiomeric resolution was obtained using (+)-dehydroabietyl-N,N-dimethylmethanaminium bis(trifluoromethane-sulfonimide) (6). The compounds 5 and 6 showed a 1:1 complexation behaviour between the host and guest. The capability of 5 and 6 to recognize the enantiomers of various α-substituted carboxylic acids and their n-Bu4N salts in enantiomeric excess (ee) determinations was demonstrated. A modification of the RES-TOCSY NMR pulse sequence is described, allowing the enhancement of enantiomeric discrimination when the resolution of multiplets is insufficient.
- Laaksonen, Tiina,Heikkinen, Sami,W?h?l?, Kristiina
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supporting information
p. 20873 - 20886
(2015/12/23)
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- Nitrilases
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The invention relates to nitrilases and to nucleic acids encoding the nitrilases. In addition, methods of designing new nitrilases and methods of use thereof are also provided. The nitrilases have increased activity and stability at increased pH and temperature.
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Paragraph 0495
(2015/09/22)
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- Soluble and functional expression of a recombinant enantioselective amidase from Klebsiella oxytoca KCTC 1686 in Escherichia coli and its biochemical characterization
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A gene encoding an enantioselective amidase (KamH) was cloned from Klebsiella oxytoca KCTC 1686 and inserted into the EcoRI and HindIII sites of the vector pET-30a(+). When KamH with a peptide containing a His-tag and an enterokinase cleavage site was overexpressed in Escherichia coli, approximately half was found in the soluble fraction, but it lacked activity. After cleavage of the peptide by enterokinase, the enzyme activity was partly restored, reaching 420.2 ± 33.62 U/g dry cell weight (DCW). Another recombinant plasmid was constructed by inserting the KamH gene into the NdeI and EcoRI sites of pET-30a(+) to express KamH in its native form. The overexpressed amidase was found primarily in the soluble fraction and its maximum activity was 3613.4 ± 201.68 U/g DCW. This indicated that the peptide influenced not only soluble expression but also activity of KamH, perhaps by blocking the substrate-binding tunnel of KamH. Similar results were obtained with heterologously expressed amidases from Rhodococcus erythropolis MP50 and Agrobacterium tumefaciens d3. All of these amidases have an N-terminal α-helical domain. Therefore, amidases of this type may be functionally expressed in their native form. KamH hydrolyzed a range of aliphatic and aromatic amides and exhibited strict S-selectivity towards racemic amides.
- Guo, Fa-Mou,Wu, Jian-Ping,Yang, Li-Rong,Xu, Gang
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p. 1264 - 1271
(2015/07/08)
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- A high-throughput screening method for determining the substrate scope of nitrilases
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Nitrile compounds are intermediates in the synthesis of pharmaceuticals such as atorvastatin. We have developed a chromogenic reagent to screen for nitrilase activity as an alternative to Nessler's reagent. It produces a semi-quantifiable blue colour and hydrolysis of 38 nitrile substrates by 23 nitrilases as cell-free extracts has been shown. This journal is
- Black, Gary W.,Brown, Nicola L.,Perry, Justin J. B.,Randall, P. David,Turnbull, Graeme,Zhang, Meng
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supporting information
p. 2660 - 2662
(2015/03/05)
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