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This paper reports the synthesis of branched alkylene guanidines using microfluidic technologies. We describe the preparation of guanidine derivatives at lower temperatures, and with significantly less time than that required in the previously applicable method. Furthermore, the use of microfluidics allows the attainment of high-purity products with a low residual monomer content, which can expand the range of applications of this class of compounds. For all the samples obtained, the molecular-weight characteristics are calculated, based on which the optimal condensation conditions are established. Additionally, in this work, the antiviral activity of the alkylene guanidine salt against the SARS-CoV-2 virus is confirmed.
Assuntos
Antivirais/síntese química , Antivirais/farmacologia , Guanidinas/síntese química , Guanidinas/farmacologia , Microfluídica/métodos , SARS-CoV-2/efeitos dos fármacos , Animais , COVID-19 , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Chlorocebus aethiops , Concentração Inibidora 50 , Espectrometria de Massas por Ionização por Electrospray , Células VeroRESUMO
Benzaldehyde lyase from Pseudomonas fluorescens Biovar I. (BAL, EC 4.1.2.38) is a versatile catalyst for the organic synthesis of chiral α-hydroxy ketones. To allow fast assessment of enzyme activity, a direct spectrophotometric assay is desirable. Here, a new robust and easy-to-handle assay based on UV absorption is presented. The assay developed is based on the ligation of the α-hydroxy ketone (R)-2,2'-furoin from 2-furaldehyde. A robust assay with direct monitoring of the product is facilitated with a convenient concentration working range minimising experimental associated with low concentrations.
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A facile reaction of 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) with dichloromethane at room temperature was observed with esters among the products. This esterification can be exploited for mild solvent-free esterification with a range of other carboxylate-based ionic liquids and alkyl halides.
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In a one-pot reaction, hydrogen peroxide generated from H(2) and O(2) on a Pd catalyst was utilised as oxidant for the TiO(2) catalyzed conversion of a sulfide to a sulfone. This transformation, where two different nanoparticle catalysts were employed in a supercritical carbon dioxide/water biphasic system, demonstrates the potential of compartmentalising catalytic processes in consecutive reactions.
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Entrapment of biocatalysts by cryogelation is a gentle method to extend the scope of biocatalysis. To foster the use of this versatile method we devised an automated injector for the production of PVA/PEG beads. The device consists of a thermostated reservoir connected to a programmable injector nozzle and an agitated receiving bath for the droplets. This lab-scale production unit yields up to 1500 beads with immobilized enzyme per minute with a narrow size distribution and good roundness.
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Automação Laboratorial/métodos , Enzimas Imobilizadas/química , Polietilenoglicóis/química , Álcool de Polivinil/química , Biotecnologia , Microscopia Eletrônica de Varredura , Microesferas , Reprodutibilidade dos Testes , TemperaturaRESUMO
Electroenzymatic syntheses combine oxidoreductase-catalysed reactions with electrochemical reactant supply. The use of ionic liquids as performance additives can contribute to overcoming existing limitations of these syntheses. Here, we report on the influence of different water-miscible ionic liquids on critical parameters such as conductivity, biocatalyst activity and stability or substrate solubility for three typical electroenzymatic syntheses. In these investigations promising ionic liquids were identified and have been used as additives for batch electrolyses on preparative scale for the three electroenzymatic systems. It was possible to improve the space-time-yield for the electrochemical regeneration of NADPH by a factor of three. For an amino acid oxidase catalysed resolution of a methionine racemate with ferrocene-mediated electrochemical regeneration of the enzyme-bound cofactor FAD a 50% increase in space time yield and 140% increase in catalyst utilisation (TTN) were achieved. Furthermore, for the chloroperoxidase-catalysed synthesis of (R)-phenylmethylsulfoxide with electrochemical generation of the required cosubstrate H2O2 the space time yield and the catalyst utilisation were improved by a factor of up to 4.2 depending on the ionic liquids used.
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Aminoácido Oxirredutases/metabolismo , Líquidos Iônicos/química , Biocatálise , Cloreto Peroxidase/metabolismo , Técnicas Eletroquímicas , Flavina-Adenina Dinucleotídeo/metabolismo , Peróxido de Hidrogênio/metabolismo , NADP/metabolismo , SolubilidadeRESUMO
Biphasic reaction media are extending the scope of technical biocatalysis. Thorough investigation of the factors affecting catalyst performance under these conditions is of key importance for the successful implementation of catalytic processes. Here, we present a reactor setup suitable for comprehensive systematic characterization and optimization of biocatalyzed reactions in biphasic systems with distinct phases. It is distinguished by small volumes allowing reproducible experimentation with minimum amounts of solvent and catalyst. The interfacial area is kept constant and independent stirring of both phases is allowed in order to minimize superimposing effects. Evaporation of low-volatile organic solvents is prevented by use of airtight construction. The broad applicability of this mini-reactor is demonstrated with regard to determination of mass transfer, enzyme productivity, and enzyme stability in both batch and continuous mode.
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Oxirredutases do Álcool/metabolismo , Aldeído Liases/metabolismo , Biocatálise , Biotecnologia/instrumentação , Solventes/metabolismo , Álcool Desidrogenase/genética , Álcool Desidrogenase/metabolismo , Oxirredutases do Álcool/genética , Aldeído Liases/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Benzaldeídos/metabolismo , Benzoína/metabolismo , Reatores Biológicos , Candida/genética , Estabilidade Enzimática , Desenho de Equipamento/instrumentação , Escherichia coli/genética , Cinética , Levilactobacillus brevis/genética , Éteres Metílicos/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Espectrofotometria UltravioletaRESUMO
Ionic liquids are considered as an alternative to organic solvents for catalysis. The literature in this field is reviewed with focus on advantageous use of ionic liquids in biocatalysis and biotransformations. The overview reveals that the exploration and mapping of ionic liquids with respect to biocatalysis is still sketchy. It is apparent that advantages can be gained in view of activity, stability and selectivity. Furthermore, integration of reaction and separation has a high potential in the field. The review presents quantitative data on the productivities, space-time yields, as well as stability as far as they can be extracted from the literature.
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Biocatálise , Biotecnologia , Líquidos Iônicos/química , Bactérias/enzimologia , Bactérias/metabolismo , Proteínas de Bactérias/metabolismo , Biotransformação , Líquidos Iônicos/metabolismo , Cinética , Estrutura MolecularRESUMO
Immobilisation of catalytically-active metal salts in ionic liquids, with extraction by supercritical carbon dioxide, affords continuous Friedel-Crafts acylation, with in situ-recycling of the catalyst.
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The number of biotransformation processes is increasing rapidly. Part of this success is based on the inherent properties of enzymes as chemo-, regio-, and enantioselective catalysts. Supercritical fluids (scF) are superior solvents inheriting adjustable and partly unique physical properties. These can be advantageously combined with biotransformations, as solvent power responds to pressure and temperature changes according to the reaction requirements. Among the scF, supercritical carbon dioxide has undoubtedly gained the highest attention. However, other scF are also recognized to enlarge the possibilities. Among these CH(4), C(2)H(6), C(2)H(4), C(3)H(8), CHF(3), and SF(6) are used as scF for biocatalysis. This review focuses on the use of non-CO(2) based scF for biotransformations. Wherever possible, special emphasis is given on the industrial viability of different biocatalytic processes.
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Catálise , Enzimas/química , Solventes/química , Dióxido de Carbono/química , SoluçõesRESUMO
An inverted supercritical carbon dioxide (scCO(2))/aqueous biphasic system has been used as reaction media for Rh-catalysed hydrogenation of polar substrates. Chiral and achiral CO(2)-philic catalysts were efficiently immobilised in scCO(2) as the stationary phase, while the polar substrates and products were contained in water as the mobile phase. Notably, product separation and catalyst recycling were conducted without depressurisation of the autoclave. The catalyst phase was reused several times with high conversion and product recovery of more than 85 %. Loss of rhodium and phosphorus by leaching were found to be below the detection limit after the first two cycles in the majority of repetitive experiments. The reaction conditions were optimised with a minimum of experiments by using a simplex algorithm in a sequential optimisation. Total turnover numbers (TTNs) of up to 1600, turnover frequencies (TOFs) of up to 340 h(-1) and ee's up to 99 % were obtained in repetitive batch operations. The scope of the devised catalytic system has been investigated and a semicontinuous reaction setup has been implemented. The chiral ligand (R,S)-3-H(2)F(6)-BINAPHOS allowed highly enantioselective hydrogenation of itaconic acid and methyl-2-acetamidoacrylate combined with a considerable catalyst stability in these reaction media.
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Biphasic reaction systems for enzyme catalysis are an elegant way to overcome limited solubility and stability of reactants and facilitate continuous processes. However, many synthetically useful enzymes are not stable in biphasic systems of water and organic solvent. The entrapment in polymer beads of polyvinyl alcohol has been shown to enable the stable operation of enzymes unstable in conventional biphasic reaction systems. We report the extension of this concept to continuous operation in a fluidised bed reactor. The enzyme benzaldehyde lyase was used for the continuous synthesis of enantiopure (R)-3,3'-furoin. The results show enhanced stability with half-life times under operation conditions of more than 100 h, as well as superior enzyme utilisation in terms of productivity. Furthermore, racemisation and oxidation of the product could be successfully prevented under the non-aqueous and inert reaction conditions.
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Aldeído Liases/química , Furanos/síntese química , Modelos Químicos , Pseudomonas fluorescens/enzimologia , Catálise , Simulação por Computador , Estabilidade Enzimática , Interações Hidrofóbicas e HidrofílicasRESUMO
Is polymer enlargement of homogeneous catalysts a tedious task? Is not batch operation with homogeneous catalysts the optimum performance point for homogeneous catalysis? Is kinetic modelling relevant to more than academic questions in homogeneous catalysis? Can all answers for a given system be answered satisfactory? In the authors' view, answers to these questions are no, no, yes, and depends. Polymer enlargement allowed the continuous operation of transfer hydrogenation in a chemical membrane reactor with total turnover numbers of up to 2.6 x 10(3) and a space-time yield of 0.58 kg L(-1) d(-1) with an enantiomeric ratio of 26.8 (enantiomeric excess 92.8 %) for a conversion level of 80 %. This was predicted from simulation conducted with a model from kinetic batch experiments adopted for continuous application. These simulations for the polymer-enlarged and the unmodified catalyst show that achieving comparable performance cannot be obtained by batch operation.
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Cetonas/química , Álcoois/química , Enzimas Imobilizadas , Hidrogenação , Cinética , Membranas Artificiais , TermodinâmicaRESUMO
Capillary electrophoresis is a powerful and versatile analytical tool due to the wide range of separation variables and separation methods possible. CE permits the combination of multiple separation mechanisms (e.g., chiral modifiers, polarity, pH) for the analysis of a large variety of compounds. The main advantage of CE (i.e., the broad range of separation variables) has thus far limited its application. This is due to the nonlinear influence and interactions of different parameters on separation quality, making it difficult to predict trends for the optimization of separation systems and hence hindering CE method development. In this paper, we present a means for rationalizing method development for CE separations using a genetic algorithm. We provide selected examples of separation enhancements achieved in the field of nucleotide and nucleotide sugar separation. An improved method for the enantioselective separation of amino acid derivatives (2-acetylamino-3-phenyl-propionic acid) will also be presented.