First green synthesis of (R)-2-methyl-1-phenylpropan-1-ol using whole-cell Lactobacillus paracasei BD101 biotransformation

Abstract

Green chemistry includes a novel process in the production of drugs precursors and biological active molecules using biocatalysts, so reducing the threats for human sanitary and ecological pollutions. Asymmetric bioreduction of prochiral ketones by biocatalysts is one of the best prevalent used methods in synthetic organic chemistry due to the production of enantiopure chiral carbinols. This study emphasizes the application biocatalyst L paracasei BD101 for enantioselective bioreduction of 2-methyl-1-phenylpropan-1-one ketone, which contain branched alkyl chain, to (R)-2-methyl-1-phenylpropan-1-ol ((R)-2) in high yields and excellent enantiomeric excess (>99%). The scale-up production was performed, and 4.61?g of (R)-2 in enantiopure form was synthesized. L paracasei BD101 was proved to be a substantial biocatalyst in asymmetric bioreduction of a ketone which contains a branched alkyl chain. There is not any work in the literature similar to our study. Hence, it is important to work on filling this gap. This study is the first example for an enantiopure synthesis of (R)-2 by a biocatalyst. The new green method was developed for bioreduction of bulky ketones, which contains a branched alkyl chain, and it approves the synthesis of novel chiral carbinols in an easy, cheap, and environmentally friendly condition using L paracasei BD101.     

Production of enantiomerically pure (S)-phenyl(pyridin-2-yl)methanol with Lactobacillus paracasei BD101

Abstract

Asymmetric reduction studies of heteroaryl ketones, including phenyl(pyridin-2-yl)methanone in enantioselective form with biocatalysts are very few, and chiral heteroaryl alcohols have been synthesized generally in the small scale. In this study, seven bacterial strains have been used to produce the (S)-phenyl(pyridin-2-yl)methanol in high enantiomeric excess and yield. Among the tested strains, Lactobacillus paracasei BD101, was found to be the best biocatalyst for the reducing phenyl(pyridin-2-yl)methanone to the (S)-phenyl(pyridin-2-yl)methanol at gram scale. The asymmetric bioreduction conditions were systematically optimized using L. paracasei BD101, which demonstrated excellent enantioselectivity and high level of conversion for the bioreduction reaction. (S)-phenyl(pyridin-2-yl)methanol, which is an analgesic, was produced enantiomerically pure form in the first time on gram scale using a biocatalyst. In total, 5.857?g of (S)-phenyl(pyridin-2-yl)methanol in enantiomerically pure form (>99% enantiomeric excess) was obtained in 52?h with 93% yield using whole cells of L. paracasei BD101. Enantiomerically pure (S)-phenyl (pyridin-2-yl)methanol, which is an analgesic, was first produced in the gram scale using a biocatalyst with excellent ee (>99%) and yield (93%).     

Whole cell application of Lactobacillus paracasei BD101 to produce enantiomerically pure (S)‐cyclohexyl(phenyl)methanol

In this study, a total of 10 bacterial strains were screened for their ability to reduce cyclohexyl(phenyl)methanone 1 to its corresponding alcohol. Among these strains, Lactobacillus paracasei BD101 was found to be the most successful biocatalyst to reduce the ketones to the corresponding alcohols. The reaction conditions were systematically optimized for the reducing agent L paracasei BD101, which showed high enantioselectivity and conversion for the bioreduction. The preparative scale asymmetric reduction of cyclohexyl(phenyl)methanone ( 1 ) by L paracasei BD101 gave (S)‐cyclohexyl(phenyl)methanol ( 2 ) with 92% yield and >99% enantiomeric excess. The preparative scale study was carried out, and a total of 5.602 g of (S)‐cyclohexyl(phenyl)methanol in high enantiomerically pure form (>99% enantiomeric excess) was produced. L paracasei BD101 has been shown to be an important biocatalyst in asymmetric reduction of bulky substrates. This study demonstrates the first example of the effective synthesis of (S)‐cyclohexyl(phenyl)methanol by the L paracasei BD101 as a biocatalyst in preparative scale.     

Production of enantiomerically enriched chiral carbinols using Weissella paramesenteroides as a novel whole cell biocatalyst

Abstract

In this study, four bacterial strains were tested for their ability to reduce acetophenones to its corresponding alcohol. Among these strains Weissella paramesenteroides N7 was found to be the most successful biocatalyst to reduce the ketones to the corresponding alcohols. The reaction conditions were systematically optimized for W. paramesenteroides N7 that resulted in high enantioselectivity and conversion rates for the bioreduction. The scale-up asymmetric reduction of 1-(4-methoxyphenyl) propan-1-one (1r) by W. paramesenteroides N7 gave (R)-1-(4-methoxyphenyl) propan-1-ol (2r) with 94% yield and >99% enantiomeric excess. This is the first report showing the synthesis of (R)-1-(4-methoxyphenyl) propan-1-ol (2r) in enantiopure form using a biocatalyst on a gram scale. The whole cell catalyzed the reductions of ketone substrates on the preparative scale, demonstrating that W. paramesenteroides N7 would be a valuable biocatalyst for the preparation of chiral aromatic alcohols of pharmaceutical interest as a promising and alternative green approach.     

Using a water-immiscible ionic liquid to improve asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one catalyzed by immobilized Candida parapsilosis CCTCC M203011 cells

Background  

Whole cells are usually employed for biocatalytic reduction reactions to ensure efficient coenzyme regeneration and to avoid problems with enzyme purification and stability. The efficiency of whole cell-catalyzed bioreduction is frequently restricted by pronounced toxicity of substrate and/or product to the microbial cells and in many instances the use of two-phase reaction systems can solve such problems. Therefore, we developed new, biphasic reaction systems with biocompatible water-immiscible ionic liquids (ILs) as alternatives to conventional organic solvents, in order to improve the asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one (TMSB) to (S)-4-(trimethylsilyl)-3-butyn-2-ol {(S)-TMSBOL}, a key intermediate for synthesis of 5-lipoxygenase inhibitors, using immobilized Candida parapsilosis CCTCC M203011 cells as the biocatalyst.     

Bio-catalytic asymmetric synthesis of β-adrenergic receptor blocker precursor: (R)-2-bromo-1-(naphthalen-2-yl)ethanol

Abstract

Aromatic α-halohydrins, particularly 2-haloethanols as significant precursor of drugs, can easily be converted to chiral β-adrenergic receptor blockers. Eight strains of Lactobacillus curvatus were tested as biocatalysts for asymmetric reduction of 2-bromo-1-(naphthalen-2-yl)ethanone 1 to 2-bromo-1- (naphthalen-2-yl) ethanol 2. The parameters of the bioreduction were optimized using L. curvatus N4, the best biocatalyst found. As a result, (R)-2-bromo-1-(naphthalen-2-yl)ethanol 2, which can be β-adrenergic receptor blocker precursor, was produced for the first time in high yield and enantiomerically pure form using biocatalysts. Moreover, the gram scale synthesis was performed and 7.54?g of (R)-2 was synthesized as enantiopure form (enantiomeric excess >99%) in 48?h. The important advantages of this process are that it produces of (R)-2 for the first time in enantiopure form, in excellent yield and under environmentally friendly and moderate reaction conditions. This system is of the potential to be applied at a commercial scale.     

Production of (R)‐1‐(1,3‐benzodioxol‐5‐yl)ethanol in high enantiomeric purity by Lactobacillus paracasei BD101

Piperonyl ring is found in a number of naturally occurring compounds and possesses enormous biological activities. There are many studies in the literature with compounds containing a piperonyl ring, but there are very few studies on the synthesis of chiral piperonyl carbinol. The objective of this study was to determine the microbial reduction ability of bacterial strains and to reveal the effects of different physicochemical parameters on this reduction ability. A total of 15 bacterial isolates were screened for their ability to reduce 1‐(benzo[d][1,3]dioxol‐5‐yl) ethanone 1 to its corresponding alcohol. Among these isolates Lactobacillus paracasei BD101 was found to be the most successful biocatalyst to reduce the ketone containing piperonyl ring to the corresponding alcohol. The reaction conditions were systematically optimized for the reducing agent L paracasei BD101, which showed high enantioselectivity and conversion for the bioreduction. The preparative scale study was performed, and a total of 3.72 g of (R)‐1‐(1,3‐benzodioxol‐5‐yl) ethanol in high enantiomeric form (>99% enantiomeric excess) was produced in a mild, cheap, and environment‐friendly process. This study demonstrates that L paracasei BD101 can be used as a biocatalyst to obtain chiral carbinol with excellent yield and selectivity.     

Green synthesis of enantiopure (S)‐1‐(benzofuran‐2‐yl)ethanol by whole‐cell biocatalyst

Optically active aromatic alcohols are valuable chiral building blocks of many natural products and chiral drugs. Lactobacillus paracasei BD87E6, which was isolated from a cereal‐based fermented beverage, was shown as a biocatalyst for the bioreduction of 1‐(benzofuran‐2‐yl) ethanone to (S)‐1‐(benzofuran‐2‐yl) ethanol with highly stereoselectivity. The bioreduction conditions were optimized using L. paracasei BD87E6 to obtain high enantiomeric excess (ee) and conversion. After optimization of the bioreduction conditions, it was shown that the bioreduction of 1‐(benzofuran‐2‐yl)ethanone was performed in mild reaction conditions. The asymmetric bioreduction of the 1‐(benzofuran‐2‐yl)ethanone had reached 92% yield with ee of higher than 99.9% at 6.73 g of substrate. Our study gave the first example for enantiopure production of (S)‐1‐(benzofuran‐2‐yl)ethanol by a biological green method. This process is also scalable and has potential in application. In this study, a basic and novel whole‐cell mediated biocatalytic method was performed for the enantiopure production of (S)‐1‐(benzofuran‐2‐yl)ethanol in the aqueous medium, which empowered the synthesis of a precious chiral intermediary process to be converted into a sophisticated molecule for drug production.     

Synthesis of Enantiomerically Enriched Drug Precursors by Lactobacillus paracasei BD87E6 as a Biocatalyst

Global sales of single enantiomeric drug products are growing at an alarming rate every year. A total of 7 bacterial strains were screened for their ability to reduce acetophenones to its corresponding alcohol. Among these strains Lactobacillus paracasei BD87E6 was found to be the most successful biocatalyst to reduce the ketones to the corresponding alcohols. The reaction conditions were systematically optimized for the reducing agent Lactobacillus paracasei BD87E6, which showed high enantioselectivity and conversion for the bioreduction. The preparative scale asymmetric reduction of 3‐methoxyacetophenone ( 1h ) by Lactobacillus paracasei BD87E6 gave (R)‐1‐(3‐methoxyphenyl)ethanol ( 2h ) with 92% yield and 99% enantiomeric excess. Compound 2h could be used for the synthesis of (S)‐rivastigmine which has a great potential for the treatment of Alzheimer's disease. This study demonstrates that Lactobacillus paracasei BD87E6 can be used as a biocatalyst to obtain chiral carbinol with excellent yield and selectivity. The whole cell catalyzed the reductions of ketone substrates on the preparative scale, demonstrating that Lactobacillus paracasei BD87E6 would be a valuable biocatalyst for the preparation of chiral aromatic alcohols of pharmaceutical interest.     

Lipase-Catalyzed Kinetic Resolution of (±)-cis-Flavan-4-ol and Its Acetate: Synthesis of Chiral 3-Hydroxyflavanones

Lipase-catalyzed kinetic resolution of (±)-cis-flavan-4-ol and its acetate led to enantiomerically enriched flavan-4-ol and its acetate. These chiral compounds were converted to (2R, 3R)- and (2S, 3S)-3-hydroxyflavanones.     

A facile synthesis of (1S,5R,6S)-5-azido-6-benzyloxycyclohex-2-en-1-ol

A facile and short synthesis of (1S,5R,6S)-5-azido-6-benzyloxycyclohex-2-en-1-ol (1) has been achieved in high yield starting from 4,5-epoxycyclohex-1-ene by using a catalytic asymmetric allylic oxidation reaction.     

Highly Enantioselective Production of Chiral Secondary Alcohols with Candida zeylanoides as a New Whole Cell Biocatalyst

The increasing demand for biocatalysts in synthesizing enantiomerically pure chiral alcohols results from the outstanding characteristics of biocatalysts in reaction, economic, and ecological issues. Herein, fifteen yeast strains belonging to three food originated yeast species Candida zeylanoides, Pichia fermentans, and Saccharomyces uvarum were tested for their capability for asymmetric reduction of acetophenone to 1‐phenylethanol as biocatalysts. Of these strains, C. zeylanoides P1 showed an effective asymmetric reduction ability. Under optimized conditions, substituted acetophenones were converted to corresponding optically active secondary alcohols in up to 99% enantiomeric excess and at high yields. The preparative scale asymmetric bioreduction of 4‐nitroacetophenone ( 1m ) by C. zeylanoides P1 gave (S)‐1‐(4‐nitrophenyl)ethanol ( 2m ) with 89% yield and > 99% enantiomeric excess. Compound 2m has been obtained in an enantiomerically pure and inexpensive form. Additionally, these results indicate that C. zeylanoides P1 is a promising biocatalyst for the synthesis of chiral alcohols in industry.     

Asymmetric Synthesis of (S)-α-Methylbenzylamine by Recombinant Escherichia coli Co-Expressing Omega-Transaminase and Acetolactate Synthase

To produce (S)-α-methylbenzylamine (MBA) from acetophenone, recombinant Escherichia coli co-expressing ω-transaminase and acetolactate synthase was used as a whole-cell biocatalyst. The solvent-bridge reaction system increased the yield of the whole-cell reaction by 2.5-fold, and the inhibitory (S)-α-MBA produced in the ω-transaminase reaction solution (pH 8.0) moved into the extraction solution (pH 3.0) via an organic solvent.     

Enantioselective hydrolysis of racemic styrene oxide and its substituted derivatives using newly-isolated Sphingopyxis sp. exhibiting a novel epoxide hydrolase activity

(S)-Styrene oxide, (S)-2-chlorostyrene oxide (CSO), (S)-3-CSO and (S)-4-CSO with 99.9 %ee were obtained with a yield of 20.6, 39.3, 28.7 and 26.8 % from 4 mM corresponding racemic substrates using 10 mg cells of a newly-isolated Sphingopyxis sp. at pH 8.0 and 25 °C in 1 ml 100 mM Tris/HCl buffer after 420, 100, 120 and 55 min, respectively. For racemic 2CSO, well-known for one of the racemates that is difficult to obtained in enantiomerically pure form, (S)-2-CSO with 99.9 %ee, 39.3 % yield (theoretical yield 50 %) and enantiomeric ratio of 42.1 was obtained. The newly-isolated strain can thus be used as whole-cell biocatalyst in the production of various (S)-CSO with a chlorine group at different positions.     

Highly selective anti-Prelog synthesis of optically active aryl alcohols by recombinant Escherichia coli expressing stereospecific alcohol dehydrogenase

Biocatalytic asymmetric synthesis has been widely used for preparation of optically active chiral alcohols as the important intermediates and precursors of active pharmaceutical ingredients. However, the available whole-cell system involving anti-Prelog specific alcohol dehydrogenase is yet limited. A recombinant Escherichia coli system expressing anti-Prelog stereospecific alcohol dehydrogenase from Candida parapsilosis was established as a whole-cell system for catalyzing asymmetric reduction of aryl ketones to anti-Prelog configured alcohols. Using 2-hydroxyacetophenone as the substrate, reaction factors including pH, cell status, and substrate concentration had obvious impacts on the outcome of whole-cell biocatalysis, and xylose was found to be an available auxiliary substrate for intracellular cofactor regeneration, by which (S)-1-phenyl-1,2-ethanediol was achieved with an optical purity of 97%e.e. and yield of 89% under the substrate concentration of 5 g/L. Additionally, the feasibility of the recombinant cells toward different aryl ketones was investigated, and most of the corresponding chiral alcohol products were obtained with an optical purity over 95%e.e. Therefore, the whole-cell system involving recombinant stereospecific alcohol dehydrogenase was constructed as an efficient biocatalyst for highly enantioselective anti-Prelog synthesis of optically active aryl alcohols and would be promising in the pharmaceutical industry.     

Asymmetric Hydrolysis of Racemic 2-Oxazolidinone Esters with Lipases

The enzymatic hydrolysis of (R, S)-5-acyloxymethyl-3-alkyl-oxazolidin-2-one I and the behavior of (S)-I for extraction with an organic solvent were examined so as to extend the biological resolution to racemates, and to learn about more appropriate combinations of substrates with lipases on the asymmetric hydrolysis. The combination of (R, S)-5-hexanoyloxymethyl-3-tert-butyl-oxazolidin-2-one 4 with lipoprotein lipase Amano 3 (L. P. L. Amano 3, origin; Pseudomonas aeruginosa) and that of (R, S)-5-octanoyloxymethyl-3-isopropyl-oxazolidin-2-one 14 with L. P. L. Amano 3 efficiently gave (S)-5-hydroxymethyl-3-tert-butyl-oxazolidin-2-one (S)-lla (99% e.e.) and (S)-5-hydroxymethyl-3-isopropyl-oxazolidin-2-one (S)-IIb (99% e.e.),respectively. (S)-IIa and (S)-IIb could be considered to be favorable intermediates for preparing optically active β-blockers.     

Enzymatic resolution of homoallyllic alcohols using various Rhizopus species

The asymmetric resolution of various 1-aryl-3-buten-1-ols via microbial hydrolysis of the corresponding acetates has been investigated using different Rhizopus species. The chosen species, R. arrhizus (wild type), efficiently hydrolyzed 1-phenyl- and 1-para-substituted phenyl-3-buten-1-ol acetates, producing the enantiomerically pure (R)-alcohols with 53–65% yields. Although the antipode acetates were obtained with 9–52% enantiomeric excess, the (S)-alcohols were amenable in > 99% enantiomeric excess via a R. arrhizus mediated asymmetric reduction of the corresponding ketones.     

Whole-cell biocatalysis: Evaluation of new hydrophobic ionic liquids for efficient asymmetric reduction of prochiral ketones

A biphasic process design is often applied in whole-cell biocatalysis if substrate and product have low water solubility, are unstable in water or toxic for the biocatalyst. Some water immiscible ionic liquids (ILs) with adequate distribution coefficients have already been applied successfully as second liquid phase, which acts as a substrate reservoir and in situ extractant for the product. In this work, 12 new ILs were evaluated with respect to their applicability in biphasic asymmetric reductions of prochiral ketones in comparison to 9 already published ILs. The ILs under study are composed of seven different cations and three different anions. Recombinant Escherichia coli was used as whole-cell biocatalyst overexpressing the genes of a Lactobacillus brevis alcohol dehydrogenase (LB-ADH) and a Candida boidinii formate dehydrogenase (CB-FDH) for cofactor regeneration. Best results were achieved if ionic liquids with [PF6]- and [NTF]-anions were applied, whereas [FAP]-ILs showed minor qualification, e.g., the use of [HMPL][NTF] as second liquid phase for asymmetric synthesis of (R)-2-octanol resulted in a space–time-yield of 180 g L⁻¹ d⁻¹, a chemical yield of 95% and an enantiomeric excess of 99.7% in a simple batch process.     

Enantioselective resolution of 2-(1-hydroxy-3-butenyl)-5-methylfuran by immobilized lipase

An efficient and convenient strategy for synthesis of enantiomerically pure S-2-(1-hydroxy-3-butenyl)-5-methylfuran was for the first time described utilizing a lipase-mediated asymmetric acylation in organic solvents. Rhizopus arrhizus lipase was chosen as the biocatalyst, and different immobilization methods including sol–gel encapsulation and covalent attachment were adopted to improve its catalytic characteristics. Various influential factors of the reaction were also investigated. Finally, the results showed that the lipase covalently attached onto epoxy resin exhibited the highest enantioselectivity and operational stability. Under optimized reaction conditions, i.e., n-hexane as the solvent, 5/1 (mol/mol) of vinyl acetate to 2-(1-hydroxy-3-butenyl)-5-methylfuran and 30 °C, the ee value of S-1 reached up to above 98% at 52% conversion with an E value of 99.     

Asymmetric Autocatalysis Induced by Chiral Crystals of Achiral Tetraphenylethylenes

The achiral hydrocarbon tetraphenylethylene crystallizes in enantiomorphous forms (chiral space group: P2₁) to afford right- and left-handed hemihedral crystals, which can be recognized by solid-state circular dichroism spectroscopic analysis. Chiral organic crystals of tetraphenylethylene mediated enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde to give, in conjunction with asymmetric autocatalysis with amplification of chirality, almost enantiomerically pure (S)- and (R)-5-pyrimidyl alkanols whose absolute configurations were controlled efficiently by the crystalline chirality of the tetraphenylethylene substrate. Tetrakis(p-chlorophenyl)ethylene and tetrakis(p-bromophenyl)ethylene also show chirality in the crystalline state, which can also act as a chiral substrate and induce enantioselectivity of diisopropylzinc addition to pyrimidine-5-carbaldehyde in asymmetric autocatalysis to give enantiomerically enriched 5-pyrimidyl alkanols with the absolute configuration correlated with that of the chiral crystals. Highly enantioselective synthesis has been achieved using chiral crystals composed of achiral hydrocarbons, tetraphenylethylenes, as chiral inducers. This chemical system enables significant amplification of the amount of chirality using spontaneously formed chiral crystals of achiral organic compounds as the seed for the chirality of asymmetric autocatalysis.