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1

Biocatalytic deracemization: An efficient one-pot synthesis of (R)-α-methyl-4-pyridinemethanol using whole cells of Candida parapsilosis

100%

Ghosh S. , Banoth L. , Banerjee U. C.

Biocatalysis

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2014

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tom 1

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nr 1

EN

A single-step synthesis of (R)-α-methyl- 4-pyridinemethanol from (RS)-α-methyl-4- pyridinemethanol by stereoinversion using whole cells of Candida parapsilosis is reported. Among the various strains of Candida species examined, C. parapsilosis demonstrated to have the best oxidoreductase system for stereoinversion of (RS)-α-methyl-4-pyridinemethanol. The effect of various physicochemical parameters on the stereoinversion process, were studied. Under optimized conditions approximately 97% enantiomeric excess of (R)-α-methyl-4-pyridinemethanol (eeR) was obtained with 99% yield was obtained. The optimized parameters were determined to be a substrate concentration of 5 mM, pH 8.0, 30°C incubation temperature, and a reaction time of 48 h. The reactions were also carried out in different organic solvents, and maximum stereoinversion was obtained in 1,4-dioxane with 78.4% eeR and 74.7% yield, which are lower than those in phosphate buffer. This whole cell catalysis for the preparation of (R)-α-methyl-4- pyridinemethanol is an example of a green, enantiopure synthesis of secondary alcohols.

2

Biocatalytic synthesis of (S)-Practolol, a selective β-blocker

88%

Mulik S. , Ghosh S. , Bhaumik J. , Banerjee U. C.

Biocatalysis

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2014

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tom 1

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nr 1

EN

The present study describes an efficient chemoenzymatic synthesis of enantiopure (S)-Practolol, a selective β-adrenergic receptor blocker. Prior to the synthesis of the target, a synthetic protocol for (RS)-N-4-(3-chloro-2-hydroxypropoxy)phenylacetamide, an essential precursor, was developed. Various commercial lipases were screened for the kinetic resolution of (RS)- N-4-(3-chloro-2-hydroxypropoxy)phenylacetamide using toluene as solvent and vinyl acetate as an acyl donor. Among various lipases screened, Pseudomonas cepacia sol-gel AK showed the highest enantioselectivity (96% enantiomeric excess with 50% conversion), affording (S)-1-(4-acetamidophenoxy)-3-chloropropan-2-yl acetate. Optimization of the reaction parameters was carried out in order to find the best-suited conditions for the biocatalysis. Furthermore, the enantiopure intermediate was hydrolyzed and the resulting product was reacted with isopropylamine to afford (S)-Practolol. This biocatalytic procedure depicts a green technology for the synthesis of (S)-Practolol with better yield and enantiomeric excess.

3

Enzymatic microreactors in biocatalysis: history, features, and future perspectives

88%

Laurenti E. , dos Santos Vianna Jr. A.

Biocatalysis

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2014

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tom 1

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nr 1

EN

Microfluidic reaction devices are a very promising technology for chemical and biochemical processes. In microreactors, the micro dimensions, coupled with a high surface area/volume ratio, permit rapid heat exchange and mass transfer, resulting in higher reaction yields and reaction rates than in conventional reactors. Moreover, the lower energy consumption and easier separation of products permit these systems to have a lower environmental impact compared to macroscale, conventional reactors. Due to these benefits, the use of microreactors is increasing in the biocatalysis field, both by using enzymes in solution and their immobilized counterparts. Following an introduction to the most common applications of microreactors in chemical processes, a broad overview will be given of the latest applications in biocatalytic processes performed in microreactors with free or immobilized enzymes. In particular, attention is given to the nature of the materials used as a support for the enzymes and the strategies employed for their immobilization. Mathematical and engineering aspects concerning fluid dynamics in microreactors were also taken into account as fundamental factors for the optimization of these systems.

4

An organic solvent and surfactant stable α-amylase from soybean seeds

75%

Jaiswal N. , Prakash O.

Acta Biochimica Polonica

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2013

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tom 60

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nr 3

387-393

EN

An organic solvent and surfactant stable α-amylase was obtained from soybean seeds. The direct and indirect effect of various organic solvents (non-polar, polar protic, and polar aprotic) and surfactants on the activity and stability of free enzyme was determined. The enzyme showed a very high catalytic efficiency and stabilization against most of the organic solvents and surfactants tested, except for few. Those organic solvents and surfactants (like chloroform, dimethyl formamide, n-butanol, and Tween 20), which caused an inhibition in enzyme activity, were used to study their effects on immobilized enzyme. The inhibitory effect was found to be decreased in immobilized enzyme as compared to free enzyme indicating that immobilization imparted stability to the enzyme. Moreover, the possibility of reuse of the enzyme in the presence of the organic solvents and surfactants was increased upon immobilization. The stability of soybean α-amylase towards organic solvents and surfactants shows that it is a potential candidate for use in organic-solvent biocatalysis as well as in detergent industries.

5

3-Hydroxycineole bioproduction from 1,8-cineole using Gymnopilus spectabilis 7423 under resting cell conditions

75%

Vega B. , Reyes B. , Rodriguez P. , Sierra W. , Gonzalez D. , Menendez P.

Biocatalysis

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2014

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tom 1

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nr 1

EN

This report describes the high yield biotransformation of 1,8-cineole by the strain Gymnopilus spectabilis 7423, a common fungus isolated from the Eucalyptus tree. The biotransformation was conducted under resting cell conditions and different parameters were tested in order to achieve up to 90% bioconversion. Only two regioisomers were detected, and they were identified as 3-α-hydroxy-1,8-cineole and 2-α-hydroxy-1,8- cineole obtained in a 82:8 ratio.

6

Zastosowanie cieczy jonowych w enzymatycznej syntezie organicznej z wykorzystaniem katalitycznych właściwości lipazy B z candida antarctica

63%

Kołodziejska R. , Jasińska L. , Karczmarska-Wódzka A. , Dramiński M.

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2010

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tom [Z] 64, 5-6

413-434

EN

In organic reactions chemical catalysts as well as catalytic proteins are used. Biocatalysts have become a useful tool for organic chemists, allowing selective, one-step syntheses. Lipases, hydrolytic enzymes, have gained a considerable attention [1]. Lipase-catalyzed reaction proceeds according to the "bi-bi ping-pong" (Scheme 1) [16]. Catalytic potential of lipases allows to obtain a wide range of organic compoundsby formation of C-C, C-N, and C-S bonds [6–8]. Enzyme-catalyzed reactions depend on change of basic-acidic properties or redox potential and an applicationof appropriate solvent can increase the control over chemical balance. The solvent used as the reaction medium should allow enzyme stability, increase its activity and selectivity. In organic hydrophobic solvents, enzyme is more stable and selective, its activity, however, is reduced in comparison to polar solvents [6–8]. During a search for optimal solvent special attention was paid to a typical organic solvents – ionic liquids. Ionic liquids are organic salts (Scheme 2) [9–13]. They do not mix with hydrophobic solvents such as hexane (Tab. 2) [9, 12, 13, 23] and their polarity is similar to low molecular weight alcohols (Tab. 3) [9, 12, 13, 22, 23, 32]. Because of their specific physical properties, ionic liquids may be optimal microenvironment for enzymes, influencing their activity and stability. CALB is widely used in organic syntheses because of its adaptive capability (Tab. 1) as well as regio- and enantioselective properties [18–21]. Due to its exceptional conformation stability in ionic liquids, CALB can be successfully applied both in heterogeneous (Tab. 4) [22, 36] and homogeneous catalysis (Scheme 4, Tab. 5) [37]. The activity of CALB after incubation in ionic liquids is comparable or greater than in conventional organic solvents (Tab. 6, Fig. 1) [9, 13, 23, 38]. A solvent used as a reaction medium should help to maintain enzyme stabilizing its active conformation and protecting it from deactivating factors such as temperature and scCO2 (Tab. 7) [38–43]. Some ionic liquids constitute a bridge between conventional organic solvents and physiological enzyme environment. They provide exceptional activity of catalytic proteins, which allows efficient and selective reaction catalysis (Tab. 8) [6,38–40, 43–61].