- Carboligation reactions mediated by benzoylformate decarboxylase immobilized on a magnetic solid support
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In this study, magnetic nanoparticles (Fe3O4, magnetite) with immobilized metal affinity ligands (MSS) were prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), and vibrating-sample magnetometer (VSM) methods for purification and immobilization of the histidine-tagged recombinant benzoylformate decarboxylase (BFD). The MSS support was shown to be eligible for selective binding of HIS-tagged BFD by SDS-page analysis. Loading capacity of the MSS support was determined as 43.6 ± 1.1 mg/g. The regeneration ability for protein binding was also studied. An immobilized BFD was tested to catalyze benzoin condensation and representative cross acyloin reaction. Conversion and enantiomeric excess values were comparable with that of free enzyme catalyzed reactions. Chirality 25:415-421, 2013.
- Tural, Bilsen,Tural, Servet,Demir, Ayhan S.
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- Stereochemistry of the Asymmetric Oxidation of Ketone Enolates Using (Camphorylsulfonyl)oxaziridines
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Asymmetric oxidation of the sodium enolates of ketones using chiral oxaziridines (+)-(2R,8aS)-1 and (-)-(2S,8aR)-2 affords α-hydroxy ketones 4 in high optical purity (69-95percent ee).An open transition state, controlled by nonbonded steric interactions, is proposed as being responsible for the chiral recognition.
- Davis, Franklin A.,Haque, Serajul M.
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- Asymmetric oxidation of silyl enol ethers using chiral dioxiranes derived from α-fluoro cyclohexanones
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Asymmetric oxidation of silyl enolethers derived from tetralone, 2-methyl-tetralone, propiophenone and deoxybenzoin using chiral dioxiranes generated in situ from oxone and new chiral α-fluorinated cyclohexanones or fructose-derived ketone have been studied. It was observed that tetrasubstituted silyl enolethers are poor substrates, that substitution at C8 of the fluoro-ketones has a significant effect on the enantioselectivities obtained and that the fructose-derived-ketone provides higher enantioselectivities. The absolute configuration of the major hydroxy ketones obtained can be rationalized using a spiro model proposed for epoxidation of olefins.
- Solladié-Cavallo,Lupattelli,Jierry,Bovicelli,Angeli,Antonioletti,Klein
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- Enantioselective C - C bond ligation using recombinant Escherichia coli-whole-cell biocatalysts
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Thiamine diphosphate (ThDP)-dependent enzymes like benzaldehyde lyase from Pseudomonas fluorescens (BAL) and benzoylformate decarboxylase from Pseudomonas putida (BFD) are versatile biocatalysts for the C - C bond ligation of aldehydes to form enantiomerically pure 2-hydroxy ketones. However, the large-scale application of this enzyme class is often restricted by the required external addition of the expensive cofactor ThDP, as well as by the common use of dimethyl sulfoxide (DMSO) as a cosolvent, which leads to problems during the work-up procedure. In the present paper we demonstrate that the addition of the excess cofactors, ThDP and magnesium ions (Mg2+), is not required when BAL or BFD are used in Escherichia coli resting cells. Furthermore, the combination of these resting cells with a biphasic reaction medium [methyl tert-butyl ether (MTBE)/aqueous buffer] allows an increase of the substrate concentration up to 1M, and an efficient extractive work-up. As a practical example, e.g., the synthesis of (R)-2-hydroxy-3,3-dimethoxy-phenylpropanone from benzaldehyde and 2,2-dimethoxyacetaldehyde was optimized, achieving an isolated yield of 78 %, and an enantiomeric excess of 98% ee in 24 h when operating at a substrate concentration of 0.4 M. The described reaction system in a biphasic medium is suitable for a wide range of aldehydes as substrates. The biphasic reaction medium minimizes also the formation of by-products, which were observed when this reaction was performed in the conventional DMSO/buffer system.
- De Maria, Pablo Dominguez,Stillger, Thomas,Pohl, Martina,Kiesel, Michael,Liese, Andreas,Groeger, Harald,Trauthwein, Harald
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- Covalent immobilization of benzoylformate decarboxylase from Pseudomonas putida on magnetic epoxy support and its carboligation reactivity
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Epoxy attached magnetic nanoparticles were prepared and used as solid support for covalent immobilization and stabilization of benzoylformate decarboxylase (BFD, E.C. 4.1.1.7) from Pseudomonas putida. A three-step immobilization/stabilization procedure is applied. The enzyme is firstly covalently immobilized under mild experimental conditions (e.g. pH 7.0, no added MgSO4 and 20 C). Secondly, the enzyme is immobilized under more drastic conditions (higher pH values, higher ionic strengths, etc.) to facilitate an increase in effective concentration of the enzyme on the support near the epoxide reactive sites. Thirdly, the remaining epoxy groups are blocked to stop any additional interaction between the enzyme and the support. With more drastic conditions, the loading of enzyme can be increased from 1.25 to 6.70 mg enzyme per gram of support. The covalently bounded enzyme was characterized in terms of its activity and stability for the formation of (S)-2-hydroxypropiophenone (2-HPP). The activity of the immobilized BFD was determined to be 53.0% related to the activity of the free enzyme. The immobilized biocatalyst retained 95% of its original activity after five reaction cycles.
- Tural, Bilsen,Tarhan, Tuba,Tural, Servet
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- Immobilization of benzaldehyde lyase and its application as a heterogeneous catalyst in the continuous synthesis of a chiral 2-hydroxy ketone
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Hexahistidine-tagged benzaldehyde lyase from E. coli SG13009/BAL HIS was immobilized by means of metal ion affinity binding to a nickel(II)-nitrilotriacetic acid derivatized carrier and applied as a heterogeneous biocatalyst in the synthesis of (R)-2-hydroxy-1-phenyl-propanone. The applicability of the immobilization by metal ion affinity binding was proven in repetitive batch reactions and in a continuously operated plug flow reactor.
- Kurlemann, Nils,Liese, Andreas
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- Fluorescence spectroscopy as a novel method for on-line analysis of biocatalytic C-C bond formations
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On-line analysis of bioprocesses is of increasing interest avoiding the time delay for off-line sample preparation and the following analyses via chromatographic methods. Moreover, continuous monitoring of the reaction components during chemo- or biocatalytic transformations provides a direct control of the process. Since productivity of the processes can be controlled simultaneously, on-line monitoring of the processes is attractive for industrial applications. The reliable in situ monitoring of biocatalyzed reactions has been a challenge where reactions run in aqueous solutions. Limited work has been published on the use of spectroscopic methods for on-line analysis of biocatalytic reactions up to now. However, in this communication two dimensional (2D)-fluorescence spectroscopy has been proved to be an effective tool for on-line monitoring of the carboligation reactions catalyzed by wild type benzoylformate decarboxylase (BFD) from Pseudomonas putida. BFD is a thiamine diphosphate (ThDP)-dependent enzyme that catalyzes the asymmetric C-C bond formation to (S)-2-hydroxypropiophenone ((S)-2-HPP) starting from benzaldehyde and acetaldehyde. The analysis of the fluorescence spectra was achieved by chemometric modeling performing principle component analysis (PCA) and partial least square (PLS) regression. The derived chemometric models were used for the validation of concentrations of yielded 2-HPP and the substrate benzaldehyde with low root mean square error of calibration (RMSEC).
- Kara, Selin,Anton, Fabienne,Solle, Doerte,Neumann, Markus,Hitzmann, Bernd,Scheper, Thomas,Liese, Andreas
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- Carboligation reactions with benzaldehyde lyase immobilized on superparamagnetic solid support
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Histidine-tagged recombinant benzaldehyde lyase (BAL, EC 4.1.2.38) was efficiently immobilized to surface-modified magnetic particles with affinity ligand binding. In addition to conventional benzoin condensation reactions, two important representative BAL-catalyzed carboligation reactions, were also performed with this magnetically responsive biocatalyst. The results obtained from the carboligation reactions that were performed with this simple and convenient heterogenous biocatalyst were comparable to that of free-enzyme-catalyzed reactions.
- Sopaci, S. Betuel,Simsek, Ilke,Tural, Bilsen,Volkan, Muervet,Demir, Ayhan S.
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- Carboligation reactivity of benzaldehyde lyase (BAL, EC 4.1.2.38) covalently attached to magnetic nanoparticles
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Epoxy-functionalized Fe3O4-SiO2 core-shell magnetic nanoparticles (epoxy-M-support) were prepared by modification with glycidyloxypropyltrimethoxysilane (GPTMS) and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FTIR) methods. Pure histidine-tagged recombinant benzaldehydelyase (BAL, EC 4.1.2.38) was efficiently immobilized onto the epoxy-M-support with covalent binding. An immobilized BAL epoxy-M-support system was tested to catalyze the self and cross condensation reactions of aldehydes, and the kinetic resolution of racemic acyloins. The acyloin products were obtained in high yield and with high enantiomeric excesses (≥98% ee). The carboligation reactivity of the immobilized enzyme was comparable to that of free enzyme-catalyzed reactions. The covalent immobilization offers high enzyme activity and stability (at least 5 repeats without losing its activity).
- Tural, Bilsen,Simsek, Ilke,Tural, Servet,Celebi, Buelent,Demir, Ayhan S.
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- Enantioselective synthesis of hydroxy ketones through cleavage and formation of acyloin linkage. Enzymatic kinetic resolution via C-C bond cleavage
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Both enantiomers of benzoins and (R)-2-hydroxy-1-phenylpropanone analogues were obtained in high yield on a preparative scale starting from aromatic aldehydes, rac-benzoins and aliphatic aldehydes via enzyme-catalysed C-C bond cleavage and C-C bond formation reactions.
- Demir,Pohl,Janzen,Mueller
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- Heterofunctional Magnetic Metal-Chelate-Epoxy Supports for the Purification and Covalent Immobilization of Benzoylformate Decarboxylase from Pseudomonas Putida and Its Carboligation Reactivity
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In this study, the combined use of the selectivity of metal chelate affinity chromatography with the capacity of epoxy supports to immobilize poly-His-tagged recombinant benzoylformate decarboxylase from Pseudomonas putida (BFD, E.C. 4.1.1.7) via covalent attachment is shown. This was achieved by designing tailor-made magnetic chelate-epoxy supports. In order to selectively adsorb and then covalently immobilize the poly-His-tagged BFD, the epoxy groups (300 μmol epoxy groups/g support) and a very small density of Co2+-chelate groups (38 μmol Co2+/g support) was introduced onto magnetic supports. That is, it was possible to accomplish, in a simple manner, the purification and covalent immobilization of a histidine-tagged recombinant BFD. The magnetically responsive biocatalyst was tested to catalyze the carboligation reactions. The benzoin condensation reactions were performed with this simple and convenient heterogeneous biocatalyst and were comparable to that of a free-enzyme-catalyzed reaction. The enantiomeric excess (ee) of (R)-benzoin was obtained at 99 ± 2% for the free enzyme and 96 ± 3% for the immobilized enzyme. To test the stability of the covalently immobilized enzyme, the immobilized enzyme was reused in five reaction cycles for the formation of chiral 2-hydroxypropiophenone (2-HPP) from benzaldehyde and acetaldehyde, and it retained 96% of its original activity after five reaction cycles. Chirality 27:635-642, 2015.
- Tural, Servet,Tural, Bilsen,Demir, Ayhan S.
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- Enzyme-catalyzed C - C bond formation using 2-methyltetrahydrofuran (2-MTHF) as (co)solvent: Efficient and bio-based alternative to DMSO and MTBE
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The enzymatic carboligation of aldehydes (C-C bond formation) catalyzed by benzaldehyde lyase (BAL) affords chiral α-hydroxy-ketones under mild reaction conditions in aqueous media. To enhance substrate and product availability under aqueous conditions, processes are often set-up using either DMSO as co-solvent, or MTBE as second organic phase. Although efficient, DMSO leads to difficulties in separation during downstream processing, with wastewater formation. MTBE provides a cleaner and straightforward work-up, but its petrochemical origin, together with its poor degradability, gives rise to environmental concerns. Herein it is reported that 2-methyltetrahydrofuran (2-MTHF) is a promising candidate to substitute DMSO or MTBE in lyase-catalyzed reactions. 2-MTHF can be derived from bio-based resources (e.g. levulinic acid), and it is abiotically degraded by air. When BAL is added to buffer-2-MTHF (5% v/v) mixtures, enzyme remains stable with a half-life of 178 ± 8 h, with productivities (benzoin synthesis) of 10 g benzoin L-1h-1. Several BAL-catalyzed aldehyde carboligations were assessed under those conditions, leading in all cases to high isolated yield (quantitative in majority), and to high enantioselectivity (up to >99%). Furthermore, preliminary results obtained with two phase systems in the BAL-catalyzed benzoin synthesis afforded 60 g benzoin L-1 in 24 h (ee > 99%). Therefore, 2-MTHF may be a valuable (co)solvent, not only to tackle environmental concerns, but also in terms of practical, efficient biocatalysis.
- Shanmuganathan, Saravanakumar,Natalia, Dessy,Van Den Wittenboer, Anne,Kohlmann, Christina,Greiner, Lasse,Dominguez De Maria, Pablo
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- Structural insights into the desymmetrization of bulky 1,2-dicarbonyls through enzymatic monoreduction
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Benzil reductases are dehydrogenases preferentially active on aromatic 1,2-diketones, but the reasons for this peculiar substrate recognition have not yet been clarified. The benzil reductase (KRED1-Pglu) from the non-conventional yeast Pichia glucozyma showed excellent activity and stereoselectivity in the monoreduction of space-demanding aromatic 1,2-dicarbonyls, making this enzyme attractive as biocatalyst in organic chemistry. Structural insights into the stereoselective monoreduction of 1,2-diketones catalyzed by KRED1-Pglu were investigated starting from its 1.77 ? resolution crystal structure, followed by QM and classical calculations; this study allowed for the identification and characterization of the KRED1-Pglu reactive site. Once identified the recognition elements involved in the stereoselective desymmetrization of bulky 1,2-dicarbonyls mediated by KRED1-Pglu, a mechanism was proposed together with an in silico prediction of substrates reactivity.
- Rabuffetti, Marco,Cannazza, Pietro,Contente, Martina Letizia,Pinto, Andrea,Romano, Diego,Hoyos, Pilar,Alcantara, Andres R.,Eberini, Ivano,Laurenzi, Tommaso,Gourlay, Louise,Di Pisa, Flavio,Molinari, Francesco
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supporting information
(2021/01/25)
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- Abiotic reduction of ketones with silanes catalysed by carbonic anhydrase through an enzymatic zinc hydride
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Enzymatic reactions through mononuclear metal hydrides are unknown in nature, despite the prevalence of such intermediates in the reactions of synthetic transition-metal catalysts. If metalloenzymes could react through abiotic intermediates like these, then the scope of enzyme-catalysed reactions would expand. Here we show that zinc-containing carbonic anhydrase enzymes catalyse hydride transfers from silanes to ketones with high enantioselectivity. We report mechanistic data providing strong evidence that the process involves a mononuclear zinc hydride. This work shows that abiotic silanes can act as reducing equivalents in an enzyme-catalysed process and that monomeric hydrides of electropositive metals, which are typically unstable in protic environments, can be catalytic intermediates in enzymatic processes. Overall, this work bridges a gap between the types of transformation in molecular catalysis and biocatalysis. [Figure not available: see fulltext.]
- Ji, Pengfei,Park, Jeeyoung,Gu, Yang,Clark, Douglas S.,Hartwig, John F.
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p. 312 - 318
(2021/02/26)
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- Continuous enzymatic stirred tank reactor cascade with unconventional medium yielding high concentrations of (S)-2-hydroxyphenyl propanone and its derivatives
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The implementation of biocatalysis in flow chemistry offers synergistic synthesis advantages in line with green chemistry principles. Yet, the conversion of high substrate concentrations is in many cases hindered by insolubility issues or substrate toxicity. Here, the continuous synthesis of (S)-2-hydroxyphenyl propanone (2-HPP) from inexpensive benzaldehyde and acetaldehyde in a methyltert-butyl ether based organic reaction environment, namely micro-aqueous reaction system, has been established. Kinetic parameters of the applied whole cell catalyst were identified to design a continuous process for (S)-2-HPP synthesis. This revealed a necessity to distribute acetaldehyde over a spatial coordinate to remain below a toxic concentration threshold. Hence, three continuous stirred tank reactors (cSTR) were conjugated in a technical cascade with an additional influx of acetaldehyde into each unit. The catalytic behaviour of this reaction setup was described based on mass balances and a kinetic model. Enzyme deactivation was described by a novel staged model and compared to a simple generic model. The optimized continuous setup yielded 190 mM (S)-HPP with an ee > 98% over 8 h. The product was easily recovered from the organic reaction environment by crystallization with an isolated yield of 68% and a purity of >99%. Further, the substrate range of the applied catalystPseudomonas putidabenzoylformate decarboxylase variant L461A was analysed. This revealed numerous halogenated, methoxylated and nitro-derivatives inortho,meta, andparaposition, which can in principle be gained by the established process. As an example, the applied cSTR concept was transferred top-methoxy benzaldehyde with good results even without further optimization.
- Glaser, Juliane,Oeggl, Reinhard,Rother, D?rte,von Lieres, Eric
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p. 7886 - 7897
(2021/12/27)
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- Novel mesoporous Ag@SiO2nanospheres as a heterogeneous catalyst with superior catalytic performance for hydrogenation of aromatic nitro compounds
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Mesoporous core-shell structure Ag@SiO2 nanospheres are constructed to prevent Ag nanoparticles from aggregation during the hydrogenation reaction. The prepared catalyst shows superior catalytic performance for hydrogenation of nitro compounds with 100% conversion and selectivity without any by-products, which also indicates good recycling performance for several times use.
- Lang, Leiming,Li, Wenyan,Lin, Xinying,Liu, Guangxiang,Long, Jing,Pan, Zhaorui,Zheng, Bo
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p. 37708 - 37712
(2021/12/09)
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- Organocatalytic Synthesis of Substituted Vinylene Carbonates
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The organocatalytic synthesis of substituted vinylene carbonates from benzoins and acyloins was studied using diphenyl carbonate as a carbonyl source. A range of N-Heterocyclic Carbene (NHC) precursors were screened and it was found that imidazolium salts were the most active for this transformation. The reaction occurs at 90 °C under solvent-free conditions. A wide range of substituted vinylene carbonates (symmetrical and unsymmetrical, aromatic or aliphatic), including some derived from natural products, were prepared with 20–99% isolated yields (24 examples). The reaction was also developed using thermomorphic polyethylene-supported organocatalysts as recoverable and recyclable species. The use of such species facilitates the workup and allows the synthesis of vinylene carbonates on the preparative scale (>30 g after 5 runs). (Figure presented.).
- Onida, Killian,Haddleton, Alice J.,Norsic, Sébastien,Boisson, Christophe,D'Agosto, Franck,Duguet, Nicolas
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supporting information
p. 5129 - 5137
(2021/09/18)
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- Zinc salt-catalyzed reduction of α-aryl imino esters, diketones and phenylacetylenes with water as hydrogen source
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The zinc salt-catalyzed reduction of α-aryl imino esters, diketones and phenylacetylenes with water as hydrogen source and zinc as reductant was successfully conducted. The presented method provides a low-cost, environmentally friendly and practical preparation of α-aryl amino esters, α-hydroxyketones and phenylethylenes. By using D2O as deuterium source, the corresponding products were obtained in high efficiency with excellent deuterium incorporation rate, which gives a cheap and safe tool for access to valuable deuterium-labelled compounds. This journal is
- Shen, Guoli,Liu, Haojie,Chen, Jingchao,He, Zhenxiu,Zhou, Yongyun,Wang, Lin,Luo, Yang,Su, Zhimin,Fan, Baomin
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supporting information
p. 3601 - 3610
(2021/05/04)
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- Preparation and Application of α-Imino Ketones through One-Pot Tandem Reactions Based on Heyns Rearrangement
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α-Imino ketone is a useful building block for the preparation of α-amino ketones and α-amino alcohols. However, its preparation has been seldomly seen. Herein, a metal-free and operationally simple strategy has been developed to generate α-imino ketones with high regioselectivity. Meanwhile, the method allowed for the preparation of various N,O-ketals with high regioselectivities and diastereoselectivities through cascade reactions in one pot.
- Li, Ling,Zhang, Shiqi,Deng, Xiongfei,Li, Guangxun,Tang, Zhuo,Zhao, Gang
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supporting information
p. 6819 - 6824
(2021/09/08)
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- Whole-Cell Biocatalysis in Seawater: New Halotolerant Yeast Strains for the Regio- and Stereoselectivity Reduction of 1-Phenylpropane-1,2-Dione in Saline-Rich Media
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The application of green chemistry concepts in catalysis has considerably increased in recent years, and the interest in using sustainable solvents in the chemical industry is growing. One of the recent proposals to fall in line with this is to employ seawater as a solvent in biocatalytic processes. This involves selecting halotolerant strains capable of carrying out chemical conversions in the presence of the salt concentrations found in this solution. Recent studies by our group have revealed the interest in using strains belonging to Debaryomyces and Schwanniomyces for catalytic processes run in this medium. In the present work, we select other yeasts based on their halotolerance to widen the scope of this strategy. We consider them for the monoreduction of 1-phenylpropane-1,2-dione, a well-characterized reaction that produces acyloin intermediates of pharmaceutical interest. The results obtained herein indicate that using seawater as a solvent for this reaction is possible. The best ones were obtained for Saccharomyces cerevisiae FY86 and Kluyveromyces marxianus, for which acyloins with different stereochemistry were obtained with good to excellent enantiomeric excess.
- Andreu, Cecilia,del Olmo, Marcellí
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p. 1621 - 1628
(2020/03/05)
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- Iron-catalyzed regiodivergent alkyne hydrosilylation
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Although tremendous effort has been devoted to the development of methods for iron catalysis, few of the catalysts reported to date exhibit clear superiority to other metal catalysts, and the mechanisms of most iron catalysis remain unclear. Herein, we report that iron complexes bearing 2,9-diaryl-1,10-phenanthroline ligands exhibit not only unprecedented catalytic activity but also unusual ligand-controlled divergent regioselectivity in hydrosilylation reactions of various alkynes. The hydrosilylation protocol described herein provides a highly efficient method for preparing useful di- and trisubstituted olefins on a relatively large scale under mild conditions, and its use markedly improved the synthetic efficiency of a number of bioactive compounds. Mechanistic studies based on control experiments and density functional theory calculations were performed to understand the catalytic pathway and the observed regioselectivity.
- Hu, Meng-Yang,He, Peng,Qiao, Tian-Zhang,Sun, Wei,Li, Wen-Tao,Lian, Jie,Li, Jin-Hong,Zhu, Shou-Fei
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p. 16894 - 16902
(2020/10/09)
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- Green preparation method α - hydroxyketone
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The invention relates to a green preparation method of alpha-hydroxyketone. The method comprises the following steps: adding ketone, iodine, 1,4-diazabicyclo[2.2.2]octane and methanol into a glass reaction bottle in sequence; then stirring and reacting for 14 to 30h at room temperature in an air atmosphere under the irradiation of a 23W compact type fluorescent lamp, so as to obtain a reaction mixture; carrying out silica gel column chromatographic separation to obtain the pure alpha-hydroxyketone. The green preparation method provided by the invention has the characteristics of greenness, high efficiency, simplicity in operation, moderate conditions, wide applicability and easiness for industrialization.
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Paragraph 0019-0022
(2020/08/27)
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- Asymmetric Oxidation of Enol Derivatives to α-Alkoxy Carbonyls Using Iminium Salt Catalysts: A Synthetic and Computational Study
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We report herein the first examples of asymmetric oxidation of enol ether and ester substrates using iminium salt organocatalysis, affording moderate to excellent enantioselectivities of up to 98% ee for tetralone-derived substrates in the α-hydroxyketone products. A comprehensive density functional theory study was undertaken to interpret the competing diastereoisomeric transition states in this example in order to identify the origins of enantioselectivity. The calculations, performed at the B3LYP/6-31G(D) level of theory, gave good agreement with the experimental results, in terms of the magnitude of the effects under the specified reaction conditions, and in terms of the preferential formation of the (R)-enantiomer. Just one of the 30 characterized transition states dominates the enantioselectivity, which is attributed to the adoption of an orientation relative to stereochemical features of the chiral controlling element that combines a CH interaction between a CH2 group in the substrate and one of the aromatic rings of the biaryl section of the chiral auxiliary with a good alignment of the acetoxy group with the other biaryl ring, and places the smallest substituent on the alkene (a hydrogen atom) in the most sterically hindered position.
- Page, Philip C. Bulman,Almutairi, Saud M.,Chan, Yohan,Stephenson, G. Richard,Gama, Yannick,Goodyear, Ross L.,Douteau, Alice,Allin, Steven M.,Jones, Garth A.
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p. 544 - 559
(2019/01/11)
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- Immobilized chiral rhodium nanoparticles stabilized by chiral P-ligands as efficient catalysts for the enantioselective hydrogenation of 1-phenyl-1,2-propanedione
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This work reports the efficient synthesis of enantio-enriched alcohols by asymmetric hydrogenation of 1-phenyl-1,2-propanedione using chiral nanoparticles (NPs) supported on SiO2. The chiral catalysts were synthesized by reducing the [Rh(μ?OCH3)(C8H12)]2 precursor under H2 in the presence of P-chiral ligands as stabilizers and SiO2 as support. Synthesis of catalysts in mild conditions was performed from labile organometallic precursor and chiral ligands provided small and well defined chiral nanoparticles (≤ 3 nm). The catalysts were characterized by XPS, HR-TEM, EDS, XRD and N2 physisorption isotherm. The physical chemical properties of the materials were correlated with the catalytic results obtained in the asymmetric hydrogenation of 1-phenyl-1,2-propanedione. In 1-phenyl-1,2-propanedione hydrogenation the best results using chiral catalysts allowed 98% conversion and enantiomeric excess of 67% to (R)-1-hydroxy-1-phenyl-propan-2-one and 59% for (R)-2-hydroxy-1-phenylpropan-1-one. Catalyst recycling studies revealed that chiral nanoparticles immobilized on SiO2 are stable. These catalysts do not need extra amount of chiral modifier or inducer added in situ and could be reused without loss of enantioselectivity.
- Ruiz, Doris,M?ki-Arvela, P?ivi,Aho, Atte,Chiment?o, Ricardo,Claver, Carmen,Godard, Cyril,Fierro, José L.G.,Murzin, Dmitry Yu.
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- Rearrangement of N- tert-Butanesulfinyl Enamines for Synthesis of Enantioenriched α-Hydroxy Ketone Derivatives
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Treating chiral N-tert-butanesulfinyl ketimines with potassium hexamethyldisilazide (or potassium tert-butoxide) and methyl triflate gives N-methylated N-tert-butanesulfinyl enamine intermediates that undergo stereoselective [2,3]-rearrangement to afford α-sulfenyloxy ketones with excellent enantiopurities. This cascade of enamination-N-methylation-rearrangement was even used to generate acyclic tertiary α-hydroxy ketones bearing two α-substituents showing negligible differences in bulkiness, such as methyl and ethyl groups.
- Li, Chun-Tian,Liu, Hui,Yao, Yun,Lu, Chong-Dao
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p. 8383 - 8388
(2019/10/14)
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- An Enzymatic 2-Step Cofactor and Co-Product Recycling Cascade towards a Chiral 1,2-Diol. Part I: Cascade Design
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Alcohol dehydrogenases are of high interest for stereoselective syntheses of chiral building blocks such as 1,2-diols. As this class of enzymes requires nicotinamide cofactors, their application in biotechnological synthesis reactions is economically only feasible with appropriate cofactor regeneration. Therefore, a co-substrate is oxidized to the respective co-product that accumulates in equal concentration to the desired target product. Co-product removal during the course of the reaction shifts the reaction towards formation of the target product and minimizes undesired side effects. Here we describe an atom efficient enzymatic cofactor regeneration system where the co-product of the ADH is recycled as a substrate in another reaction set. A 2-step enzymatic cascade consisting of a thiamine diphosphate (ThDP)-dependent carboligase and an alcohol dehydrogenase is presented here as a model reaction. In the first step benzaldehyde and acetaldehyde react to a chiral 2-hydroxy ketone, which is subsequently reduced by to a 1,2-diol. By choice of an appropriate co-substrate (here: benzyl alcohol) for the cofactor regeneration in the alcohol dehydrogenases (ADH)-catalyzed step, the co-product (here: benzaldehyde) can be used as a substrate for the carboligation step. Even without any addition of benzaldehyde in the first reaction step, this cascade design yielded 1,2-diol concentrations of >100 mM with optical purities (ee, de) of up to 99%. Moreover, this approach overcomes the low benzaldehyde solubility in aqueous systems and optimizes the atom economy of the reaction by reduced waste production. The example presented here for the 2-step recycling cascade of (1R,2R)-1-phenylpropane-1,2-diol can be applied for any set of enzymes, where the co-products of one process step serve as substrates for a coupled reaction. (Figure presented.).
- Kulig, Justyna,Sehl, Torsten,Mackfeld, Ursula,Wiechert, Wolfgang,Pohl, Martina,Rother, D?rte
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supporting information
p. 2607 - 2615
(2019/05/24)
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- Influenza virus replication inhibitors and uses thereof (by machine translation)
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The invention provides a compound as an influenza virus replication inhibitor, a method for preparing the same, a pharmaceutical composition containing the compound and application. (by machine translation)
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- Regio- and stereoselective multi-enzymatic aminohydroxylation of β-methylstyrene using dioxygen, ammonia and formate
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We report an enzymatic route for the formal regio- and stereoselective aminohydroxylation of β-methylstyrene that consumes only dioxygen, ammonia and formate; carbonate is the by-product. The biocascade entails highly selective epoxidation, hydrolysis and hydrogen-borrowing alcohol amination. Thus, β-methylstyrene was converted into 1R,2R and 1S,2R-phenylpropanolamine in 59-63% isolated yields, and up to >99.5 : 0.5 dr and er.
- Corrado, Maria L.,Knaus, Tanja,Mutti, Francesco G.
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supporting information
p. 6246 - 6251
(2019/12/03)
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- Solvent-Free Synthesis of α-Amino Ketones from α-Hydroxyl Ketones via A Novel Tandem Reaction Sequence Based on Heyns Rearrangement
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Heyns rearrangement have been famous for carbohydrate chemists for several decades. However, this reaction was underrated as a useful method for synthetic chemists due to preparative shortcomings. Herein we developed an efficient method for the synthesis of pharmaceutically important α-amino ketones from readily available α-hydroxy ketones and secondary amines through a tandem reaction sequence based on Heyns rearrangement. The reaction smoothly proceeded by using catalytic PTSA as catalyst without solvent. Primary and secondary α-hydroxy ketones were readily used and regioselectively afforded the correspondingly α-amino ketones with moderate yield.
- Li, Ling-Yu,Zeng, Qing-Le,Li, Guang-Xun,Tang, Zhuo
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supporting information
p. 694 - 699
(2019/03/26)
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- Spiro[indene-1,4′-oxa-zolidinones] Synthesis via Rh(III)-Catalyzed Coupling of 4-Phenyl-1,3-oxazol-2(3 H)-ones with Alkynes: A Redox-Neutral Approach
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Transition-metal-catalyzed C-H activation synthesis of heterocyclic spiro[4,4]nonanes has persistently witnessed the use of additional stoichiometric transition-metal oxidant when employing C=C bond as the spiro ring closure site. Herein, we have addressed the issue by reporting a redox-neutral strategy for spiro[indene-1,4′-oxa-zolidinones] synthesis via Rh(III)-catalyzed coupling of 4-phenyl-1,3-oxazol-2(3H)-ones with alkynes. The synthesis features a broad substrate scope and high regiospecificity.
- Liu, Zhongsu,Zhang, Wenjing,Guo, Shan,Zhu, Jin
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p. 11945 - 11957
(2019/10/02)
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- Kinetic resolution of racemic 2-hydroxyamides using a diphenylacetyl component as an acyl source and a chiral acyl-transfer catalyst
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Various optically active 2-hydroxyamide derivatives are produced based on the kinetic resolution of racemic 2-hydroxyamides with a diphenylacetyl component and (R)-benzotetramisole ((R)-BTM), a chiral acyl-transfer catalyst, via asymmetric esterification and acylation. It was revealed that a tertiary amide can be used with this novel protocol to achieve high selectivity (22 examples; s-value reaching over 250). The resulting chiral compounds could be transformed into other useful structures while maintaining their chirality.
- Murata, Takatsugu,Kawanishi, Tatsuya,Sekiguchi, Akihiro,Ishikawa, Ryo,Ono, Keisuke,Nakata, Kenya,Shiina, Isamu
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- Kinetic Resolution of α-Hydroxy-Substituted Oxime Ethers by Enantioselective Cu?H-Catalyzed Si?O Coupling
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A catalyst-controlled enantioselective alcohol silylation by Cu?H-catalyzed dehydrogenative Si?O coupling of hydroxy groups α to an oxime ether and simple hydrosilanes is reported. The selectivity factors reached in this kinetic resolution are generally high (s≈50), and these reactions thereby provide reliable access to highly enantioenriched α-hydroxy-substituted oxime ethers. The synthetic usefulness of these compounds is also demonstrated.
- Dong, Xichang,Kita, Yuji,Oestreich, Martin
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p. 10728 - 10731
(2018/08/17)
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- Expanding the Substrate Specificity of Thermoanaerobacter pseudoethanolicus Secondary Alcohol Dehydrogenase by a Dual Site Mutation
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Here, we report the asymmetric reduction of selected phenyl-ring-containing ketones by various single- and dual-site mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). The further expansion of the size of the substrate binding pocket in the mutant W110A/I86A not only allowed the accommodation of substrates of the single mutants W110A and I86A within the expanded active site but also expanded the substrate range of the enzyme to ketones bearing two sterically demanding groups (bulky–bulky ketones), which are not substrates for the TeSADH single mutants. We also report the regio- and enantioselective reduction of diketones with W110A/I86A TeSADH and single TeSADH mutants. The double mutant exhibited dual stereopreference to generate the Prelog products most of the time and the anti-Prelog products in a few cases.
- Musa, Musa M.,Bsharat, Odey,Karume, Ibrahim,Vieille, Claire,Takahashi, Masateru,Hamdan, Samir M.
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p. 798 - 805
(2018/02/21)
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- Stereo- and Regioselectivity in Catalyzed Transformation of a 1,2-Disubstituted Vicinal Diol and the Corresponding Diketone by Wild Type and Laboratory Evolved Alcohol Dehydrogenases
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ADH-A from Rhodococcus ruber DSM 44541 catalyzes the oxidation of (S)-1-phenylethanol 3000-fold more efficiently as compared with the 2-hydroxylated derivative (R)-phenylethane-1,2-diol. The enzyme is also highly selective for sec-alcohols with comparably low activities with the corresponding primary alcohols. When challenged with a substrate containing two secondary alcohols, such as 1-phenylpropane-(1R,2S)-diol, ADH-A favors the oxidation of the benzylic carbon of this alcohol. The catalytic efficiency, however, is modest in comparison to the activity with (S)-1-phenylethanol. To investigate the structural requirements for improved oxidation of vicinal diols, we conducted iterative saturation mutagenesis combined with activity screening. A first-generation variant, B1 (Y54G, L119Y) displays a 2-fold higher kcat value with 1-phenylpropane-(1R,2S)-diol and a shift in the cooperative behavior in alcohol binding, from negative in the wild type, to positive in B1, suggesting a shift from a less active enzyme form (T) in the wild type to a more active form (R) in the B1 variant. Also, the regiopreference changed to favor oxidation of C-2. A second-generation variant, B1F4 (F43T, Y54G, L119Y, F282W), shows further improvement in the turnover and regioselectivity in oxidation of 1-phenylpropane-(1R,2S)-diol. The crystal structures of the B1 and B1F4 variants describe the structural alterations to the active site, the most significant of which is a repositioning of a Tyr side-chain located distal to the coenzyme and the catalytic zinc ion. The links between the changes in structures and stereoselectivities are rationalized by molecular dynamics simulations of substrate binding at the respective active sites.
- Maurer, Dirk,Enugala, Thilak Reddy,Hamnevik, Emil,Bauer, Paul,Lüking, Malin,Petrovi?, Du?an,Hillier, Heidi,Kamerlin, Shina C. L.,Dobritzsch, Doreen,Widersten, Mikael
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p. 7526 - 7538
(2018/07/21)
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- Asymmetric synthesis of α-trifluoromethoxy ketones with a tetrasubstituted α-stereogenic centre via the palladium-catalyzed decarboxylative allylic alkylation of allyl enol carbonates
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The palladium-catalyzed asymmetric decarboxylative allylic alkylation of trifluoromethoxy allyl enol carbonates afforded enantioenriched α-trifluoromethoxy allyl ketones that feature a tetrasubstituted α-stereogenic center in excellent yield and high enantioselectivity. The method was further extended to the asymmetric synthesis of α-difluoromethoxy and α-methoxy allyl ketones, which proceeded under similar catalytic conditions.
- Kondo, Hiroya,Maeno, Mayaka,Hirano, Kazuki,Shibata, Norio
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supporting information
p. 5522 - 5525
(2018/06/04)
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- NON-IONIC LOW DIFFUSING PHOTO-ACID GENERATORS
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Non-ionic photo-acid generating (PAG) compounds were prepared that contain an aryl ketone group. The disclosed non-polymeric PAGs release a strong sulfonic acid when exposed to high energy radiation such as deep UV or extreme UV light. The photo-generated sulfonic acid has a low diffusion rate in an exposed resist layer subjected to a post-exposure bake (PEB) at 100° C. to 150° C., resulting in formation of good line patterns after development. At higher temperatures, the PAGs undergo a thermal reaction to form a sulfonic acid.
- -
-
Paragraph 0184; 0185
(2018/03/09)
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- Assessing the stereoselectivity of: Serratia marcescens CECT 977 2,3-butanediol dehydrogenase
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α-Hydroxy ketones and vicinal diols constitute well-known building blocks in organic synthesis. Here we describe one enzyme that enables the enantioselective synthesis of both building blocks starting from diketones. The enzyme 2,3-butanediol dehydrogenase (BudC) from S. marcescens CECT 977 belongs to the NADH-dependent metal-independent short-chain dehydrogenases/reductases family (SDR) and catalyses the selective asymmetric reductions of prochiral α-diketones to the corresponding α-hydroxy ketones and diols. BudC is highly active towards structurally diverse diketones in combination with nicotinamide cofactor regeneration systems. Aliphatic diketones, cyclic diketones and alkyl phenyl diketones are well accepted, whereas their derivatives possessing two bulky groups are not converted. In the reverse reaction vicinal diols are preferred over other substrates with hydroxy/keto groups in non-vicinal positions.
- Médici, Rosario,Stammes, Hanna,Kwakernaak, Stender,Otten, Linda G.,Hanefeld, Ulf
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p. 1831 - 1837
(2017/07/15)
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- Flow-based stereoselective reduction of ketones using an immobilized ketoreductase/glucose dehydrogenase mixed bed system
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A robust two-enzyme system composed of an immobilized ketoreductase (KRED1-Pglu) and a glucose dehydrogenase (BmGDH) was developed via immobilization on aldehyde agarose for the stereoselective reduction of different ketones. The immobilized ketoreductase/glucose dehydrogenase system was continuously used in a flow reactor for weeks, even in the presence of concentrations of DMSO up to 20%.
- Dall'Oglio, Federica,Contente, Martina Letizia,Conti, Paola,Molinari, Francesco,Monfredi, Danila,Pinto, Andrea,Romano, Diego,Ubiali, Daniela,Tamborini, Lucia,Serra, Immacolata
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- Halogen-bonded iodonium ion catalysis: A route to α-hydroxy ketones: Via domino oxidations of secondary alcohols and aliphatic C-H bonds with high selectivity and control
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A domino synthesis of α-hydroxy ketones has been developed from benzylic secondary alcohols employing catalytic iodonium ions stabilized by DMSO. The reaction proceeds through an unprecedented sequential oxidation of alcohols to ketone and its α-hydroxylation in a controlled manner. The spectroscopic evidence establishes the possibility of formation of a stable halogen-bonded adduct between DMSO and iodonium ions.
- Guha, Somraj,Kazi, Imran,Mukherjee, Pranamita,Sekar, Govindasamy
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p. 10942 - 10945
(2017/10/13)
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- Α - hydroxy ketone compound low priced high-efficient synthetic method
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The invention discloses a cheap and efficient synthesis method of an alpha-hydroxyketone compound. The synthesis method is characterized in that a carbonyl compound undergoes an oxidation hydroxylation reaction at 10-120DEG C under normal pressure with iodine simple substance, N-bromosuccimide, copper bromide, bromine simple substance, hydrogen bromide, N-iodosuccimide or hydrogen iodide as a catalyst, sulfoxide as an oxidant, water or sulfoxide as a hydroxy source and sulfoxide, ethyl acetate, N,N-dimethyl formamide, acetonitrile, toluene, 1,4-dioxane, 1,2-dichloroethane, tetrahydrofuran or H2O as a solvent, and converts into the alpha-hydroxyketone compound in a high selectivity manner. Compared with traditional synthesis methods, the method disclosed in the invention has the advantages of simple operation, high yield, simple conditions, easy purification, small waste discharge amount, simple reaction apparatus, and easy industrial production. The method has wide applicability and can be used for synthesizing various alpha-hydroxyketone compounds.
- -
-
Paragraph 0036-0075
(2017/08/25)
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- N,N-Dimethylformamide (DMF) as a Source of Oxygen to Access α-Hydroxy Arones via the α-Hydroxylation of Arones
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An unprecedented α-hydroxylation strategy was developed for the synthesis of α-hydroxy arones using N,N-dimethylformamide (DMF) as an oxygen source. Control experiments demonstrated that the oxygen atom of the hydroxy group in the α-hydroxy arones produced in this reaction was derived from DMF. This new reaction therefore not only provides an alternative strategy for the α-hydroxylation of arones but also highlights the possibility of using the inexpensive common solvent DMF as a source of oxygen in organic synthesis.
- Liu, Weibing,Chen, Cui,Zhou, Peng
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p. 2219 - 2222
(2017/02/26)
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- Stereoselective reduction of aromatic ketones by a new ketoreductase from Pichia glucozyma
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A new NADPH-dependent benzil reductase (KRED1-Pglu) was identified from the genome of the non-conventional yeast Pichia glucozyma CBS 5766 and overexpressed in E. coli. The new protein was characterised and reaction parameters were optimised for the enantioselective reduction of benzil to (S)-benzoin. A thorough study of the substrate range of KRED1-Pglu was conducted; in contrast to most other known ketoreductases, KRED1-Pglu prefers space-demanding substrates, which are often converted with high stereoselectivity. A molecular modelling study was carried out for understanding the structural determinants involved in the stereorecognition experimentally observed and unpredictable on the basis of steric properties of the substrates. As a result, a new useful catalyst was identified, enabling the enantioselective preparation of different aromatic alcohols and hydroxyketones.
- Contente, Martina Letizia,Serra, Immacolata,Brambilla, Marta,Eberini, Ivano,Gianazza, Elisabetta,De Vitis, Valerio,Molinari, Francesco,Zambelli, Paolo,Romano, Diego
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p. 193 - 201
(2016/01/09)
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- Regio- and Stereoselective Aliphatic–Aromatic Cross-Benzoin Reaction: Enzymatic Divergent Catalysis
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The catalytic asymmetric synthesis of chiral 2-hydroxy ketones by using different thiamine diphosphate dependent enzymes, namely benzaldehyde lyase from Pseudomonas fluorescens (PfBAL), a variant of benzoylformate decarboxylase from?Pseudomonas putida (PpBFD-L461A), branched-chain 2-keto acid decarboxylase from Lactococcus lactis (LlKdcA) and a variant of pyruvate decarboxylase from Acetobacter pasteurianus (ApPDC-E469G), was studied. Starting with the same set of substrates, substituted benzaldehydes in combination with different aliphatic aldehydes, PfBAL and PpBFD-L461A selectively deliver the (R)- and (S)-2-hydroxy-propiophenone derivatives, respectively. The (R)- and (S)-phenylacetylcarbinol (1-hydroxy-1-phenylacetone) derivatives are accessible in a similar way using LlKdcA and ApPDC-E469G, respectively. In many cases excellent stereochemical purities (>98 % enantiomeric excess) could be achieved. Hence, the regio- and stereochemistry of the product in the asymmetric aliphatic–aromatic cross-benzoin reaction can be controlled solely by choice of the appropriate enzyme or enzyme variant.
- Beigi, Maryam,Gauchenova, Ekaterina,Walter, Lydia,Waltzer, Simon,Bonina, Fabrizio,Stillger, Thomas,Rother, D?rte,Pohl, Martina,Müller, Michael
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supporting information
p. 13999 - 14005
(2016/09/21)
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- Modularized Biocatalysis: Immobilization of Whole Cells for Preparative Applications in Microaqueous Organic Solvents
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The use of whole-cell biocatalysts enables catalyst application in microaqueous reaction systems, in which the liquid phase consists of high substrate loadings in organic solvents, to enable access to high concentrations of easy-to-purify product. One current research focus is the modularization of single reaction steps to (i)enable flexible combinations into multi-step enzyme reactions, (ii)investigate ideal reaction conditions, and (iii)facilitate catalyst handling and recycling. Therefore, we published the easy-to-apply encapsulation of a lyophilized whole-cell catalyst in a polymeric membrane recently. These catalytic "teabags" were demonstrated to enable flexible catalyst combinations for multi-step reactions and excellent recyclability during repeated batch experiments. We now describe the applicability of these "teabags" on a larger scale by using the new SpinChem reactor and a classical stirred-tank reactor model. As an alternative, we investigate the described alginate entrapment approach and compare the results. The carboligation reaction towards (R)-benzoin, using lyophilized E.coli that enclose Pseudomonas fluorescens benzaldehyde lyase (EC 4.1.2.38), served as a model reaction. It was demonstrated that the catalytic "teabags" are scalable and perform equally on the investigatory 5mL scale and the preparative 140mL reactor scale. Tested in a more advanced application, the "teabags" were proven to be useful in a one-pot two-step reaction for the gram-scale production of 1-phenylpropane-1,2-diol by using the SpinChem reactor, which allowed to reach an industrially relevant product concentration (32.9g L-1) and space-time yield (8.2g L-1 d-1).
- Wachtmeister, Jochen,Mennicken, Philip,Hunold, Andreas,Rother, D?rte
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p. 607 - 614
(2016/02/20)
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- Stereoselective Two-Step Biocatalysis in Organic Solvent: Toward All Stereoisomers of a 1,2-Diol at High Product Concentrations
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Biotransformations on larger scale are mostly limited to cases in which alternative chemical routes lack sufficient chemo-, regio-, or stereoselectivity. Here, we expand the applicability of biocatalysis by combining cheap whole cell catalysts with a microaqueous solvent system. Compared to aqueous systems, this permits manifoldly higher concentrations of hydrophobic substrates while maintaining stereoselectivity. We apply these methods to four different two-step reactions of carboligation and oxidoreduction to obtain 1-phenylpropane-1,2-diol (PPD), a versatile building block for pharmaceuticals, starting from inexpensive aldehyde substrates. By a modular combination of two carboligases and two alcohol dehydrogenases, all four stereoisomers of PPD can be produced in a flexible way. After thorough optimization of each two-step reaction, the resulting processes enabled up to 63 g L-1 product concentration (98% yield), space-time-yields up to 144 g L-1 d-1, and a target isomer content of at least 95%. Despite the use of whole cell catalysts, we did not observe any side product formation of note. In addition, we prove that, by using 1,5-pentandiol as a smart cosubstrate, a very advantageous cofactor regeneration system could be applied.
- Wachtmeister, Jochen,Jakoblinnert, Andre,Rother, D?rte
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p. 1744 - 1753
(2016/10/31)
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- Iodine Promoted Regioselective α-Sulfenylation of Carbonyl Compounds using Dimethyl Sulfoxide as an Oxidant
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A metal-free regioselective sulfenylation of the α-CH3 group of ketones has been achieved in the presence of the α-CH2 or α-CH group using the cross dehydrogenative (CDC) strategy. Aldehydes also exhibit good selectivity forming the corresponding α-sulfenylated products. This efficient sulfenylation of ketones or aldehydes with thiones or heterocyclic thiols utilizes dimethyl sulfoxide (DMSO) as an oxidant in the presence of iodine. This eco-friendly method uses readily available and inexpensive I2 and DMSO. The application of this methodology has been demonstrated by synthesizing precursors for Julia- Kocienski olefination intermediates.
- Siddaraju, Yogesh,Prabhu, Kandikere Ramaiah
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supporting information
p. 6090 - 6093
(2016/12/09)
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- Biocatalytic route to chiral acyloins: P450-catalyzed regio- and enantioselective α-hydroxylation of ketones
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P450-BM3 and mutants of this monooxygenase generated by directed evolution are excellent catalysts for the oxidative α-hydroxylation of ketones with formation of chiral acyloins with high regioselectivity (up to 99%) and enantioselectivity (up to 99% ee). This constitutes a new route to a class of chiral compounds that are useful intermediates in the synthesis of many kinds of biologically active compounds.
- Agudo, Rubén,Roiban, Gheorghe-Doru,Lonsdale, Richard,Ilie, Adriana,Reetz, Manfred T.
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p. 950 - 956
(2015/01/30)
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- Reversibility of asymmetric catalyzed C-C bond formation by benzoylformate decarboxylase
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Benzoylformate decarboxylase (BFD) from Pseudomonas putida catalyzed the formation of 2-hydroxy-1-phenylpropanone (2-HPP), a 2-hydroxy ketone, from the kinetic resolution of rac-benzoin in the presence of acetaldehyde. The formation rate of 2-HPP via kinetic resolution of benzoin was 700-fold lower compared to the formation via direct carboligation of benzaldehyde and acetaldehyde. Further investigations revealed that BFD not only accepts (R)-benzoin but also 2-HPP as the substrate. A typical Michaelis-Menten type kinetics was observed starting from enantiopure (S)- or (R)-2-HPP. The formation of racemic 2-HPP while using benzoin as the donor in the presence of acetaldehyde and the racemization of (R/S)-2-HPP were detected. The equilibrium constant determined, showed favoured conditions towards the product side i.e. (R)-benzoin and 2-HPP. In the end, an extended reaction mechanism was proposed by supplementing the already known mechanism with the C-C bond cleavage activity of BFD towards 2-hydroxy ketones. This journal is
- Berheide, Marco,Kara, Selin,Liese, Andreas
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p. 2418 - 2426
(2015/04/14)
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- Immobilised chiral inducer on Pt-based mesoporous titanate nanotubes as heterogeneous catalysts for enantioselective hydrogenation
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A new series of chiral porous titanate nanotubes (TNTs) containing (-)-11-trimethoxysilyl-cinchonidine (TMS-CD) moieties were synthesized via direct surface anchorage. These hybrid solids were used as supports for Pt (1 wt%) catalysts and evaluated in heterogeneous enantioselective hydrogenation of 1-phenyl-1,2-propanodione. The supports and catalysts were characterized by a variety of techniques including TGA, N2 adsorption isotherms, solid state NMR (13C and 29Si), XRD, HR-TEM, DRIFTs and XPS. For the best system the hydrogen pressure, solvent effects and recycles were studied. The maximum enantiomeric excess (ee) and the turnover frequency obtained under optimized conditions with 1% Pt/TNT-CD were 37% (at 15 wt% nominal content of TMS-CD) and 165 min-1 (at 10 wt% nominal content of TMS-CD), respectively. The variation of H2 pressure and solvent affects both the activity and enantioselectivity due to the substrate adsorption on the metal active sites. Additionally, these heterogeneous catalysts can also be easily recycled and reused for three times without the loss of activity and enantioselectivity. After the 3rd cycle, catalyst deactivation due to the leaching of Pt nanoparticles and modifier hydrogenation in the feed was detected.
- Campos, Cristian H.,Torres, Cecilia C.,Osorio-Vargas, Paula,Mella, Claudio,Belmar, Julio,Ruiz, Doris,Fierro, José L.G.,Reyes, Patricio
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p. 190 - 202
(2015/02/19)
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- Regio- and enantioselective reduction of diketones: Preparation of enantiomerically pure hydroxy ketones catalysed by Candida parapsilosis ATCC 7330
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Enantiomerically enriched hydroxy ketones were prepared by the reduction of the corresponding diketones with excellent enantiomeric excess (98%) and in good yields (up to 75%) using whole cells of Candida parapsilosis ATCC 7330. Cyclic diketones, such as 1,2-cyclohexanedione and 1,4-cyclohexanedione, resulted in hydroxy ketones as products. Cyclohexane-1,3-dione and 5,5-dimethylcyclohexane-1,3-dione gave dimerised products, such as 2,2′-(ethane-1,1-diyl)bis(3-hydroxycyclohex-2-enone) and 2,2′-(ethane-1,1-diyl)bis(3-hydroxy-5,5-dimethylcyclohex-2-enone) with acetaldehyde generated in situ from whole cells of Candida parapsilosis ATCC 7330, which is reported here for the first time.
- Mahajabeen, Pula,Chadha, Anju
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p. 1167 - 1173
(2015/10/28)
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- I2- or NBS-catalyzed highly efficient α-hydroxylation of ketones with dimethyl sulfoxide
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An efficient method for the direct preparation of high synthetic valuable α-hydroxycarbonyls is described. The simple and readily available I2 or NBS was used as catalyst. DMSO acts as the oxidant, oxygen source, and solvent. A diverse range of tertiary Csp3-H bonds as well as more challenging secondary Csp3-H bonds could be hydroxylated in this transformation. The reaction is mild, less toxic and easy to perform.
- Liang, Yu-Feng,Wu, Kai,Song, Song,Li, Xinyao,Huang, Xiaoqiang,Jiao, Ning
-
supporting information
p. 876 - 879
(2015/04/14)
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- Iodine promoted α-hydroxylation of ketones
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A novel method for α-hydroxylation of ketones using substoichiometric amount of iodine under metal-free conditions is described. This method has been successfully employed in synthesizing a variety of heterocyclic compounds, which are useful precursors. α-Hydroxylation of diketones and triketones are illustrated. This strategy provides a novel, efficient, mild and inexpensive method for α-hydroxylation of aryl ketones using a sub-stoichiometric amount of molecular iodine.
- Siddaraju, Yogesh,Prabhu, Kandikere Ramaiah
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supporting information
p. 6749 - 6753
(2015/06/25)
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- Selective oxidation of benzylic, allylic and propargylic alcohols using dirhodium(II) tetraamidinate as catalyst and aqueous tert-butyl hydroperoxide as oxidant
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We show that the dirhodium(II) tetraamidinate complex Rh2(Msip)4 efficiently catalyzes the oxidation of activated secondary alcohols at only 0.1 mol% loading. In this approach, we oxidized various benzylic, allylic and propargylic alcohols to the corresponding carbonyl compounds under mild aqueous conditions using the inexpensive oxidant T-HYDRO (70 wt% aqueous tert-butyl hydroperoxide).
- Wusiman, Abudureheman,Lu, Chong-Dao
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p. 254 - 258
(2015/03/30)
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- Enantioselective oxidation of 1,2-diols with quinine-derived urea organocatalyst
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Quinine-derived urea has been identified as a highly efficient organocatalyst for the enantioselective oxidation of 1,2-diols using bromination reagents as the oxidant. This simple procedure utilizes readily available reagents and operates at ambient temperature to yield a wide range of α-hydroxy ketones in good yield (up to 94%) and excellent enantioselectivity (up to 95% ee).
- Rong, Zi-Qiang,Pan, Hui-Jie,Yan, Hai-Long,Zhao, Yu
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p. 208 - 211
(2014/01/23)
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- Enantioselective hydrogenation of 1-phenyl-1,2-propanodione on cinchonidine-modified Rh/MCM-41 catalysts
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Enantioselective hydrogenation of 1-phenyl-1,2-propanodione (PPD) on Rh/MCM-41 catalysts was studied. The catalysts were prepared using Rh(acac) 3 as a metal precursor and metal loadings that ranged from 0.5 to 1.5 wt%. The samples were characterised by nitrogen adsorption-desorption isotherms at 77 K using ICP-MS, XRD, TEM, XRD and XPS. The reaction was performed at 298 K, and 0.01 mol L-1 of PPD and cinchonidine (CD) was used as chiral modifier. The effect of the modifier concentration on the enantioselectivity (ee) and the conversion level in the hydrogenation reaction shows a relationship between the activity and ee as well as the CD concentration. The volcano-type curve observed for each catalyst suggests competitive adsorption of the modifier and substrate on the catalyst surface. The metal loading influences both the Rh crystallite size and catalytic behaviour. An increase in the Rh levels was accompanied by a parallel increase in both the crystallite size and number of Rh ensembles with a subsequent enhancement in both the conversion level and ee. The catalyst with the highest metal loading was 1.0 wt% Rh/MCM-41, and it displayed the highest ee among the catalysts studied. Additionally, the effects of hydrogen pressure and solvent nature on the catalytic activity were also studied. Moreover, the H2 pressure also influenced the conversion levels with only a minor effect on the ee values. Considering the solvent effects, we observed non-linear ee dependence with an increasing solvent dielectric constant, which showed a decrease in conversion levels in the order cyclohexane > toluene > tetrahydrofurane > dichloromethane.
- Torres, Cecilia C.,Campos, Cristian H.,Fierro,Reyes, Patricio,Ruiz, Doris
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p. 321 - 328
(2014/07/08)
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- Enantioselective hydrogenation of 1-phenyl-1,2-propanedione on immobilised cinchonidine-TiO2 catalysts
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The enantioselective hydrogenation of 1-phenyl-1,2-propanodione (PPD) was investigated using cinchonidine-immobilised Pt/TiO2 catalysts. Prior to metal deposition, TiO2 was chirally modified by the direct anchoring of cinchonidine (CD) using trimethoxysilane as coupling agent (TMS-CD). The catalysts were prepared using a high H2 pressure reduction-deposition method and were characterised by elemental analysis (C, H and N), TG, DRIFT, 13C and 29Si solid-state NMR, N 2 adsorption-desorption isotherms, XRD, XPS and HR-TEM. The catalytic activity was evaluated in a batch reactor at 298 K and 40 bar using cyclohexane as solvent with various cinchonidine concentrations. The results indicate that the enantioselectivity was sensitive to the CD surface concentration and the enantiomeric excess of the target product, 1-R-phenyl-1-hydroxy-2-propanone, was in the range of 25-51%. The best catalyst was the one supported on TiO 2 with a nominal content of 10 wt% TMS-CD. The effect of the H 2 pressure, the concentration of substrate, solvent and recyclability of the catalyst were studied. The results obtained confirmed that the variation of reaction conditions affects both the activity and enantioselectivity due to the substrate adsorption on the metal active sites. Concerning the solvent effect, the enantiomeric excess decreased non-linearly upon increasing the solvent dielectric constant; this was attributed to the interactions between solvents and TMS-CD on the surface. In the catalyst recycling studies, the enantiomeric excess decreased up to 40% after the 3rd reuse. The drop of activity and enantiomeric excess was attributed to the hydrogenation of the immobilised CD.
- Campos, Cristian H.,Torres, Cecilia C.,Dongil, Ana B.,Ruiz, Doris,Fierro, José L.G.,Reyes, Patricio
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p. 226 - 236
(2014/08/18)
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- Preparation of polymer incarcerated gold nanocluster catalysts (PI-Au) and their application to aerobic oxidation reactions of boronic acids, alcohols, and silyl enol ethers
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Heterogeneous gold nanocluster catalysts immobilized by the method known as polymer incarceration were prepared. Polystyrene-derived polymers with epoxide and alcohol moieties, which could be cross-linked under heating conditions, were employed as supports for their preparation. Cationic gold salts were reduced in a solution of NaBH4 and the polymers. Poor solvents for the polymers were added, and the polymers were precipitated and encapsulated gold nanoclusters with weak but multiple interactions between a gold nanocluster surface and the π electrons of benzene rings. The polymer capsules were heated under neat conditions to afford heterogeneous gold nanocluster catalysts; namely, polymer-incarcerated gold nanoclusters. The catalysts thus prepared could be applied to the aerobic oxidation of phenyl boronic acids, alcohols, and silyl enol ethers. We found that the choice of polymers, good and poor solvents for the polymers, metal loadings, heating conditions for cross-linking, and final activation were all crucial for obtaining high-activity catalysts.
- Miyamura, Hiroyuki,Yasukawa, Tomohiro,Kobayashi, Shu
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p. 6039 - 6049
(2015/03/30)
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- Whole-cell teabag catalysis for the modularisation of synthetic enzyme cascades in micro-aqueous systems
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Combining enzymes to form multi-step enzyme cascades has great potential to replace existing chemical routes with high atom-efficient and eco-efficient synthesis strategies as well as to grant access to new products, especially those with multi-stereogenic centres. However, easy solutions and tools for setting up appropriate reaction conditions and process modes are hardly available. The utilisation of teabags filled with whole cells has several advantages, such as 1) simplified handling and recovery of catalyst, 2) easy combination of various catalysts from catalyst toolboxes, 3) fast testing of different operating modes during cascadation and 4) simplified downstream processing. One of the main advantages is that lyophilised whole-cell catalysts can be applied in micro-aqueous media, allowing high substrate loads (also of poorly water-soluble substrates) and concomitantly enabling high catalyst stability. This was demonstrated herein for a synthetic two-step cascade towards chiral 1,2-diols starting from cheap aldehydes. The carboligation of two aldehydes using Pseudomonas fluorescens benzaldehyde lyase and subsequent oxidoreduction with Ralstonia sp. alcohol dehydrogenase yielded 1-phenylpropane-1,2-diol [(1R,2R)-PPD] in concentrations of up to 339 mM and excellent enantiomeric and diastereomeric excesses >99 %. Therefore, the combination of whole-cell catalysis and teabag modularisation allows cheap, easy-to-apply and efficient catalyst preparation to test enzyme combinations and optimal reaction conditions up to the preparative scale. By circumventing catalyst purification and immobilisation, and enabling high substrate loadings compared to those in aqueous systems, efficient production of a chiral diol with extraordinarily high product concentrations can be achieved. Biocatalysis in teabags: For the modularization of synthetic enzyme cascades, teabag-like containers are filled with lyophilised whole-cell catalyst. The bags are tight, recyclable, and easy-to-prepare and handle. Applied in a micro-aqueous system enabling high substrate loadings, stereoselective synthesis of diols was accomplished with high product concentrations and simplified catalyst and product separation.
- Wachtmeister, Jochen,Jakoblinnert, Andre,Kulig, Justyna,Offermann, Heike,Rother, Doerte
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p. 1051 - 1058
(2014/05/06)
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- A two-step biocatalytic cascade in micro-aqueous medium: Using whole cells to obtain high concentrations of a vicinal diol
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Although single- and multi-step biocatalytic approaches show persuasive advantages for the synthesis of especially chiral compounds (e.g. high chemo- and stereoselectivity), their application often suffers from low substrate loads and hence low space-time-yields. We herein present a synthetic cascade approach in which lyophilised, recombinant whole cells are applied in micro-aqueous reaction systems yielding extremely high space-time-yields. As an example we investigated the two-step synthesis of 1-phenylpropane-1,2-diol starting from cheap aldehydes and achieved high selectivities (ee/de > 99%) and high product concentrations. The new concept of running biocatalytic cascades in a mixture of high substrate loads and organic solvents under addition of small amounts of highly concentrated buffer is not only very easy-to-apply, but also exhibits several economic and ecologic advantages. On the one hand the usage of whole, lyophilised cells circumvents time-consuming enzyme purification as well as addition of expensive cofactors (here ThDP and NADPH). Additionally, catalyst and product workup is facilitated by the application of organic solvents (here MTBE). On the other hand, the employment of whole cells very effectively circumvents stability problems of biocatalysts in unconventional media enabling the addition of extremely high substrate loads (up to 500 mM in our example) and is therefore an easy and effective approach for multi-step biocatalysis. After optimisation, the combination of a carboligation step followed by a second oxidoreduction step with whole cell catalysts afforded an efficient two-step cascade for the production of 1-phenylpropane-1,2-diol with space-time yields up to 327 g L-1 d-1 and an E-factor of 21.3 kg waste kgproduct-1. This journal is the Partner Organisations 2014.
- Jakoblinnert, Andre,Rother, Doerte
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supporting information
p. 3472 - 3482
(2014/07/08)
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- Regio- and enantio-selective oxidation of diols by Candida parapsilosis ATCC 7330
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Selectivity between primary and secondary alcohols was observed in oxidation using whole cells of Candida parapsilosis ATCC 7330, where the secondary alcohol was preferentially oxidized. In racemic sec alcohols, the 'R' enantiomer was selectively oxidized to the corresponding keto alcohol (yield = 18-54%) leaving the 'S' diol (yield = 31-69% and enantiomeric excess from 14% to >99%). A biphasic system consisting of isooctane-water (48 : 2 v/v) was used as a medium for biotransformation at 25 °C. This is the first report of the regio- and enantio-selective oxidation of diols using C. parapsilosis ATCC 7330.
- Sivakumari, Thakkellapati,Chadha, Anju
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p. 60526 - 60533
(2015/02/19)
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