Synthesis Of Chiral Alcohols Research Articles

Ketoreductase TpdE from Rhodococcus jostii TMP1: characterization and application in the synthesis of chiral alcohols.

Background. Production of highly pure enantiomers of vicinal diols is desirable, but difficult to achieve. Enantiomerically pure diols and acyloins are valuable bulk chemicals, promising synthones and potential building blocks for chiral polymers. Enzymatic reduction of ketones is a useful technique for the synthesis of the desired enantiomeric alcohols. Here, we report on the characterization of a ketoreductase TpdE from Rhodococcus jostii TMP1 that is a prospective tool for the synthesis of such compounds.Results. In this study, NADPH-dependent short-chain dehydrogenase/reductase TpdE from Rhodococcus jostii TMP1 was characterized. The enzyme exhibited broad substrate specificity towards aliphatic 2,3-diketones, butan-3-one-2-yl alkanoates, as well as acetoin and its acylated derivatives. TpdE stereospecifically reduced α-diketones to the corresponding diols. The GC-MS analysis of the reduction products of 2,3- and 3,4-diketones indicated that TpdE is capable of reducing both keto groups in its substrate leading to the formation of two new chiral atoms in the product molecule. Bioconversions of diketones to corresponding diols occurred using either purified enzyme or a whole-cell Escherichia coli BL21 (DE3) biocatalyst harbouring recombinant TpdE. The optimum temperature and pH were determined to be 30–35 °C and 7.5, respectively.Conclusions. The broad substrate specificity and stereoselectivity of TpdE from Rhodococcus jostii TMP1 make it a promising biocatalyst for the production of enantiomerically pure diols that are difficult to obtain by chemical routes.

A genomic search approach to identify carbonyl reductases in Gluconobacter oxydans for enantioselective reduction of ketones

The versatile carbonyl reductases from Gluconobacter oxydans in the enantioselective reduction of ketones to the corresponding alcohols were exploited by genome search approach. All purified enzymes showed activities toward the tested ketoesters with different activities. In the reduction of 4-phenyl-2-butanone with in situ NAD(P)H regeneration system, (S)-alcohol was obtained with an e.e. of up to 100% catalyzed by Gox0644. Under the same experimental condition, all enzymes catalyzed ethyl 4-chloroacetoacetate to give chiral products with an excellent e.e. of up to 99%, except Gox0644. Gox2036 had a strict requirement for NADH as the cofactor and showed excellent enantiospecificity in the synthesis of ethyl (R)-4-chloro-3-hydroxybutanoate. For the reduction of ethyl 2-oxo-4-phenylbutyrate, excellent e.e. (>99%) and high conversion (93.1%) were obtained by Gox0525, whereas the other enzymes showed relatively lower e.e. and conversions. Among them, Gox2036 and Gox0525 showed potentials in the synthesis of chiral alcohols as useful biocatalysts.

A solar light-driven, eco-friendly protocol for highly enantioselective synthesis of chiral alcohols via photocatalytic/biocatalytic cascades

The judicious utilization of solar light for the asymmetric synthesis of optically active compounds by imitating natural photosynthesis introduces a new concept that harnesses this renewable energy in vitro for ultimate transformation into chiral chemical bonds. Herein, we present a comprehensive description of such a biomimetic endeavor towards the design and construction of an asymmetric artificial photosynthesis system that comprises an efficient method of nicotinamide cofactor (NADPH) regeneration under visible light employing a graphene-based light harvesting photocatalyst and its subsequent utilization in an enzyme-catalyzed asymmetric reduction of prochiral ketones to expediently furnish the corresponding chiral secondary alcohols. A detailed optimization study revealed a major dependency of the reaction outcome on the amount of cofactor, photocatalyst and enzyme used, as well as the mode of their addition. A series of structurally diverse ketones bearing an array of (hetero)aryl/alkyl substituents proved to be highly suitable to our photocatalytic–biocatalytic cascade approach, providing (R/S)-1-(hetero)aryl/alkylethanols in excellent enantioselectivities (ee ∼ 95–>99.9%) under mild and environmentally benign conditions. To the best of our knowledge, the synthesis of these enantiopure alcohols employing a visible-light-driven nicotinamide cofactor regeneration strategy has been reported for the first time. Such enantioenriched alcohols act as versatile chiral building blocks for the synthesis of compounds having industrial and pharmaceutical relevance. In addition, this solar-to-chiral chemicals prototype appears advantageous from ecological and economical perspectives. We describe mechanistic pathways to demonstrate how the present catalytic synthesis protocol functions through perfect orchestration between visible-light-driven photocatalysis and biocatalysis to be successively applied in inducing asymmetry in an achiral molecule for the ultimate goal of solar energy utilization in the synthesis of valuable chiral fine chemicals. This work highlights the potential advantages of a bioinspired system to the pertinence of solar energy in asymmetric transformations leading to enantioenriched alcohol precursors, and thus opens up a new field of research that might emerge as an important breakthrough with promising implications towards generating a sustainable and non-fossil/non-nuclear energy future.

Cyclopropane intermediates in the synthesis of chiral alcohols with methyl-branched carbon skeleton. Application in the synthesis of insect pheromones

Several chiral building blocks, (2R)-2-methylundec-10-en-1-ol, (3R)-3-methylheptan-1-ol, and (4R)-4-methyloctan-1-ol, have been synthesized using cyclopropane intermediate products. It has been shown that the obtained chiral alcohols can be used in the synthesis of insect pheromones.

Biocatalytic synthesis of chiral alcohols and amino acids for development of pharmaceuticals.

Chirality is a key factor in the safety and efficacy of many drug products and thus the production of single enantiomers of drug intermediates and drugs has become increasingly important in the pharmaceutical industry. There has been an increasing awareness of the enormous potential of microorganisms and enzymes derived there from for the transformation of synthetic chemicals with high chemo-, regio- and enatioselectivities. In this article, biocatalytic processes are described for the synthesis of chiral alcohols and unntural aminoacids for pharmaceuticals.

Asymmetric rearrangement of racemic epoxides catalyzed by chiral Brønsted acids

This paper describes a chiral Brønsted acid catalyzed asymmetric 1,2-rearrangement of racemic epoxides via a hydrogen-shift process for the synthesis of chiral aldehydes, and, followed by a reduction, a variety of optically active alcohols can be furnished in moderate yields with up to 50% ee. Especially, a facile one-pot synthesis of chiral alcohols directly from simple alkenes by a sequential epoxidation, rearrangement, and reduction has also been realized.

Access to Optically Active Aryl Halohydrins Using a Substrate-Tolerant Carbonyl Reductase Discovered from Kluyveromyces thermotolerans

By genome data mining, a carbonyl reductase tool box was designed and developed for chiral alcohol synthesis. On the basis of systematic comparison of the specific activity and substrate tolerance toward α-chloroacetophenone among reductases in this tool box, KtCR, a highly substrate-/product-tolerant carbonyl reductase from Kluyveromyces thermotolerans, was identified. The reduction of a series of substituted aryl ketones was investigated using this newly mined biocatalyst. Almost all of the ketones tested were asymmetrically reduced into corresponding chiral alcohols in 99% ee. Substrates with substituents adjacent to the carbonyl group or those with substituents on the para position of the phenyl ring were easier to reduce. For α-choloacetophenone as a representative substrate, as much as 154 g/L (1.0 M) of the substrate was asymmetrically reduced within merely 12 h by lyophilized cells of Escherichia coli/pET28-KtCR, resulting in an isolated yield of 92%, an enantiopurity of >99% ee, and a total turno...

Multi‐Enzymatic Cascade Reactions: Overview and Perspectives

AbstractMulti‐enzymatic cascade reactions, i.e., the combination of several enzymatic transformations in concurrent one‐pot processes, offer considerable advantages: the demand of time, costs and chemicals for product recovery may be reduced, reversible reactions can be driven to completion and the concentration of harmful or unstable compounds can be kept to a minimum. This review summarizes the developments in multi‐enzymatic cascades employed for the asymmetric synthesis of chiral alcohols, amines and amino acids, as well as for CC bond formation. In addition, a general classification of biocatalytic cascade systems is provided and bioprocess engineering aspects associated with the topic are discussed.

Highly efficient synthesis of chiral alcohols with a novel NADH-dependent reductase from Streptomyces coelicolor

An NADH-dependent reductase (ScCR) from Streptomyces coelicolor was discovered by genome mining for carbonyl reductases. ScCR was overexpressed in Escherichia coli BL21, purified to homogeneity and its catalytic properties were studied. This enzyme catalyzed the asymmetric reduction of a broad range of prochiral ketones including aryl ketones, α- and β-ketoesters, with high activity and excellent enantioselectivity (>99% ee) towards β-ketoesters. Among them, ethyl 4-chloro-3-oxobutanoate (COBE) was efficiently converted to ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE), an important pharmaceutical intermediate, in water/toluene biphasic system. As much as 600g/L (3.6M) of COBE was asymmetrically reduced within 22h using 2-propanol as a co-substrate for NADH regeneration, resulting in a yield of 93%, an enantioselectivity of >99% ee, and a total turnover number (TTN) of 12,100. These results indicate the potential of ScCR for the industrial production of valuable chiral alcohols.

Utilising hardly-water soluble substrates as a second phase enables the straightforward synthesis of chiral alcohols

So far, the alcohol dehydrogenase-catalysed conversion of longer chain aliphatic substrates has been challenging due to their low solubility in aqueous solution. However, by utilising the ketone directly as a second organic phase, the straightforward synthesis of long chain aliphatic chiral alcohols is enabled.

Microbial synthesis of chiral alcohols using a novel monooxygenase

Microbial synthesis of chiral alcohols using a novel monooxygenase

New kinetic and thermodynamic approach of one-pot synthesis of chiral alcohol by oxidoreductase from Candida parapsilosis

The stereoinversion process involving two sequential stereoselective oxidation and reduction reactions by oxidoreductases was a typical and important one-pot method for chiral secondary alcohol synthesis which has great potential for industrial application. The process to produce (S)-1-phenyl-1,2-ethanediol with whole cell was chosen as a model reaction to investigate the kinetic and thermodynamic properties of key enzymes which catalyzed the single oxidation and reduction step of the whole reaction. The kinetic data from initial rate experiments in the absence of product prove that both oxidation and reduction reactions follow Theorell-Chance BiBi mechanism. Parameters of V m and Δ S suggest that the oxidation reaction was thermodynamically unfavorable and the restrictive step of the one-pot process was inhibited at high concentration of substrate PED. To remove the inhibition of substrate, extractive biocatalytic methods were successfully applied to improve the substrate PED concentration from 15 g/l to 50 g/l with high optical purity of 91.6% and yield of 82.5%.

An Efficient Synthesis of Chiral Alcohols via Catalytic Hydrogenation of Esters

A ruthenium complex was found to catalyze the hydrogenation of chiral esters without the loss of their optical purities under mild and neutral conditions. This method can avoid a violent quench step and an extraction step which accompany conventional reduction using metal hydride reagents such as sodium borohydride and lithium aluminum hydride.

Practical chiral alcohol manufacture using ketoreductases

Over the past two years the application of ketoreductases in the commercial synthesis of chiral alcohols has undergone a revolution. Biocatalysts are now often the preferred catalyst for the synthesis of chiral alcohols via ketone reduction and are displacing reagents and chemocatalysts that only recently were considered break-through process solutions themselves. Tailor-made enzymes can now be generated from advanced, non-natural variants using HTP screening and modern molecular biology techniques. At the same time, global economic and environmental pressures direct industrial process development toward versatile platforms that can be applied to the different stages of product development. We will discuss the technologies that have emerged over the past years that have guided biocatalysis from the bottom of the toolbox, to the power tool of choice.

New oxidoreductases from cyanobacteria for asymmetric synthesis of chiral alcohols

New oxidoreductases from cyanobacteria for asymmetric synthesis of chiral alcohols

Stable Electroenzymatic Processes by Catalyst Separation

Division of labour: The rapid enzyme inactivation in the electroenzymatic synthesis of chiral alcohols has been the main obstacle for synthetic applications during the last two decades. The reasons for this inactivation have now been elucidated. The development of a water-soluble polymeric mediator and the spatial separation of enzyme and mediator led to the first stable process and significantly improved catalyst utilisations (see picture).

Microscale Synthesis of Chiral Alcohols via Asymmetric Catalytic Transfer Hydrogenation

Synthesis of pure enantiomers is a key issue in industry, especially in areas connected to life sciences. Catalytic asymmetric synthesis has emerged as a powerful and practical tool. Here we describe an experiment on racemic reduction and asymmetric reduction via a catalytic hydrogen transfer process. Acetophenone and substituted acetophenones are reduced by NaBH4 either in the presence or in the absence of β-cyclodextrin, and by isopropanol in the presence of a rhodium catalyst with cyclopentadienyl and 1-amino-2-indanol ligands. After analysis by chiral gas chromatography, enantiomeric excess, conversion, and turnover frequency can be calculated. This experiment is suitable for upper-level undergraduate students. The experiment can be completed in a four hour laboratory session. It can also be extended in many ways: the influence of parameters such as reaction time; catalyst or substrate concentration; or temperature or catalyst type can be analyzed.

Identification, Cloning, and Characterization of a Novel Ketoreductase from the Cyanobacterium Synechococcus sp. Strain PCC 7942

A new ketoreductase useful for asymmetric synthesis of chiral alcohols was identified in the cyanobacterium Synechococcus sp. strain PCC 7942. Mass spectrometry of trypsin-digested peptides identified the protein as 3-ketoacyl-[acyl-carrier-protein] reductase (KR) (EC 1.1.1.100). The gene, referred to as fabG, was cloned, functionally expressed in Escherichia coli, and subsequently purified to homogeneity. The enzyme displayed a temperature optimum at 44 degrees C and a broad pH optimum between pH 7 and pH 9. The NADPH-dependent KR was able to asymmetrically reduce a variety of prochiral ketones with good to excellent enantioselectivities (>99.8%). The KR showed particular high specific activity for asymmetric reduction of ethyl 4-chloroacetoacetate (38.29 +/- 2.15 U mg(-1)) and 2',3',4',5',6'-pentafluoroacetophenone (8.57 +/- 0.49 U mg(-1)) to the corresponding (S)-alcohols. In comparison with an established industrial enzyme like the alcohol dehydrogenase from Lactobacillus brevis, the KR showed seven-times-higher activity toward 2',3',4',5',6'-pentafluoroacetophenone, with a remarkably higher enantiomeric excess (>99.8% [S] versus 43.3% [S]).

Purification and characterization of a novel carbonyl reductase with high stereo-selectivity

A novel NADPH-dependent carbonyl reductase was separated from Candida parapsilosis CCTCC 203011. The enzyme gave a single band on sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE), which was purified through ammonium sulfate, Diethylamino Ethanol (DEAE) sepharose Fast flow (FF), phenyl-sepharose FF and blue sepharose FF chromatography from cell-free extract. The molecular mass of the enzyme was about 30 kDa. The optimum pH and temperature for reduction were 4.5°C and 35°C, respectively. The Cu2+ had strong restrictive effect on enzyme activity. In addition, the carbonyl reductase was an enzyme with high substrate specificity and stereo-selectivity, and showed high asymmetric reduction activity towards α-hydroxyacetophenone and ethyl 4-chloro acetoacetate. For the asymmetric reduction of α-hydroxyacetophenone and ethyl 4-chloro acetoacetate, (S)-1-phenyl-1,2-ethanediol and (R)-ethyl4-chloro-3-hydroxybutanoate were produced by the purified enzyme, with the 100% and 94.3% e.e. value, respectively. Therefore, the enzyme could be one of the effective biocatalysts for asymmetric synthesis of chiral alcohols. The amino acid sequences of one peptide from the purified enzyme were analyzed by LC-MASS-MASS, and the carbonyl reductase showed some identity to the hypothetical protein CaO19.10414 reported.

Electroenzymatic synthesis of chiral alcohols in an aqueous–organic two-phase system

The reduction of acetophenone to ( R)-phenylethanol catalysed by the alcohol dehydrogenase from Lactobacillus brevis in combination with electrochemical regeneration of NADPH mediated by a rhodium complex is reported. The reaction in buffer solution was optimised with regard to high productivity (up to 14 gL −1d −1) and enantioselectivity (>99.9%). Enzyme stability under the reaction conditions was increased either by addition of bovine serum albumin as a sacrificial protein or by immobilisation, leading to full conversion and enzyme ttn’s of up to 75,000. To improve the utilisation of cofactor and mediator as well as to broaden the substrate spectrum to more hydrophobic substrates, we introduced an organic phase of methyl tert-butyl ether. This is the first reported two-phase approach for electrochemical cofactor regeneration, which yielded mediator and cofactor ttn’s twice as high as in the one-phase approach. Furthermore, a concentrated product solution of 180 mM enantiopure ( R)-phenylethanol was obtained, facilitating product work-up.