Lipase-catalyzed Enantioselective Esterification Research Articles

Lipase/Oxovanadium Co-Catalyzed Dynamic Kinetic Resolution of Propargyl Alcohols: Competition between Racemization and Rearrangement.

Quantitative conversion of racemic propargyl alcohols into optically active propargyl esters with up to 99% ee has been achieved by lipase/oxovanadium co-catalyzed dynamic kinetic resolution, which combines the lipase-catalyzed enantioselective esterification of the racemic substrates and the in situ racemization of the remaining enantiomers. The success is owed to our discovery of a magic solvent, (trifluoromethyl)benzene, that accelerated the racemization while sufficiently suppressing the common oxovanadium-catalyzed rearrangement of propargyl alcohols to irreversibly produce enals.

A green resolution–separation process for aliphatic secondary alcohols

In order to obtain both enantiomers of aliphatic secondary alcohols via a greener method, the four-step resolution–separation process involving lipase-catalyzed enantioselective esterification and hydrolysis as well as two separation procedures both via heterogeneous azeotropic distillation was developed. (S)-2-Pentanol (ee=98.6%), (R)-2-pentanol (ee >99%), (S)-2-octanol (ee=98.2%), and (R)-2-octanol (ee=98.5%) were all produced in high purity (>98%) and high yield (>90%). In addition to the two model substrates, this method could also be applied to the resolution of other aliphatic secondary alcohols.

Kinetic Resolution of Racemic 1-Phenyl 1-Propanol by Lipase Catalyzed Enantioselective Esterification Reaction

In this study, resolution of (R,S)-1-phenyl 1-propanol by lipase-catalyzed enantioselective esterification was achieved. To investigate the effect of lipase type on enantiomeric excess, three different lipases were used. Novozym 435 exhibited the highest enantioselectivity for resolution of (R,S)-1-phenyl 1-propanol. The effects of carbon length of fatty acids from C12 to C16, which were used as acyl donor, organic solvents with Log P values from 0.5 to 4.5, acyl donor/alcohol molar ratio (1:1, 3:2, 2:1, 3:1), amount of added molecular sieves (0-133.2 kg/m(3)), and temperature (10-60° C) on the enantioselectivity were investigated. The best reaction conditions were comprised of using toluene (Log P= 2.5) as solvent, lauric acid (12C) as acyl donor, 133.2 kg/m(3) molecular sieves at 50° C and acyl donor/alcohol molar ratio as 1:1. Under these conditions, the enantiomeric excess of S enantiomer ee (S) was obtained as 95% for a reaction time of 2.5 hours.

ChemInform Abstract: Lipase-Catalyzed Enantioselective Esterification of 2-Methylalkanoic Acids.

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ChemInform Abstract: Remote Control of Stereoselectivity: Lipase-Catalyzed Enantioselective Esterification of Racemic α-Lipoic Acid.

Abstract Lipase of Candida rugosa (E.C.3.1.1.3) catalyzes the enantioselective esterification of racemic 6,8-dithioctic acid (α-lipoic acid) with aliphatic alcohols in hexane. Although the reaction centre is four carbon atoms away from the stereogenic centre, (S)-esters with enantioselectivity dependent upon the chain length of alcohol are obtained. A model for the active site of the enzyme is suggested.

Solvent Versatility of Immobilized Amylose and Cellulose-Based Chiral Stationary Phases in Enantioselective LC Separation and Monitoring of Bio-Catalyzed Resolutions of Acidic Drugs in Non-Standard Organic Solvents

The solvent versatility of Chiralpak IA (amylose tris(3,5-dimethylphenylcarbamate)), Chiralpak IB (cellulose tris(3,5-dimethylphenylcarbamate)) and Chiralpak IC (cellulose tris(3,5-dichlorophenylcarbamate)) immobilized onto silica gel, are investigated for the enantioselective separation of a set of acidic drugs in liquid chromatography. Non-standard LC organic solvents like dichloromethane, ethyl acetate, tetrahydrofuran, methyl-tert-butyl ether were used in mobile phase compositions and/or diluent agent for the analyte on all new columns. Furthermore, the enantioselective separations of the reported compounds were compared on both immobilized columns (Chiralpak IA and IB) and their conventionally coated versions (Chiralpak AD-H and Chiralcel OD-H, respectively), using a mixture of n-hexane/2-PrOH/TFA (80:20:0.1 v/v/v). The versatility of the immobilized Chiralpak IB in monitoring reactions performed in non-standard solvent was studied on a representative example consisting of the lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol in methyl-tert-butyl ether as organic solvent.

Molecular modeling and experimental verification of lipase-catalyzed enantioselective esterification of racemic naproxen in supercritical carbon dioxide

Experimental and simulation analyses were performed on the lipase-catalyzed esterification reaction of racemic naproxen by CALB (candida antarctica lipase B) enzyme in supercritical carbon dioxide. The reaction pathways were investigated by quantum mechanical analysis, and the enantioselectivity of the products was predicted by molecular dynamics simulation analysis. Calculated results from molecular modeling in supercritical carbon dioxide were qualitatively compared with experimental data by using racemic naproxen as a substrate. All molecular modeling results and experimental data were acquired and compared with those in ambient and supercritical condition. Moreover, to verify the stability of enzymatic reaction in each solvent condition, reaction pathways were investigated in several solvent conditions (vacuum, water, hexane and supercritical carbon dioxide), and the stability of enzymatic reaction in supercritical carbon dioxide was compared with other solvent conditions.

PH Memory of Immobilized Lipase for (±)-Menthol Resolution in Ionic Liquid

Magnetic DEAE-GMA-EDMA microspheres were prepared via suspension polymerization and used for the immobilization of Candida rugosa lipase by ion exchange. The effect of pH values on the immobilization of lipase was investigated. Resolution of (+/-)-menthol in the hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was performed by immobilized lipase-catalyzed enantioselective esterification with propionic anhydride as acyl donor. The effects of pH condition at lipase immobilization on the conversion and enantioselectivity were investigated. As a result, pH memory of the immobilized lipase for catalyzing (+/-)-menthol resolution in the ionic liquid was observed. Better conversion and the best enantioselectivity were obtained with the immobilized lipase prepared at pH 5.0. Under the condition, (-)-menthyl propionate with enantiomeric excess of >90% was obtained. Moreover, the enantioselectivity of the immobilized lipase decreased gradually with increasing pH value.

Effect of methyl branching of C8H18 alkanes and water activity on lipase-catalyzed enantioselective esterification of ibuprofen

The purpose of this research was to study the effect of the methyl branching of a high log P alkane solvent and the water activity in the organic medium on the initial rate and the enantioselectivity of ibuprofen esterification catalyzed by Candida rugosa lipase. Resolution of ibuprofen is important because S-(+)-ibuprofen has the desired pharmacological activity, whereas the R-(-)-enantiomer causes much of the side effects. The Candida rugosa lipase-catalyzed reaction in isooctane at 40oC and 0.73 water activity gave the best results, both in terms of the initial reaction rate and the enantioselectivity of the reaction. An increase in water activity allowed a higher reaction rate and enantiomeric excess in each of the four solvents. An increase in methyl branching did not necessarily increase the initial reaction rate, but it allowed a higher enantioselectivity, evidenced by an increase in the substrate enantiomeric excess

Effect of methyl branching of C8H18 alkanes and water activity on lipase-catalyzed enantioselective esterification of ibuprofen

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Optimization of lipase-catalyzed enantioselective esterification of (±)-menthol in ionic liquid

Response surface methodology was successfully applied to optimize lipase-catalyzed enantioselective esterification of (±)-menthol. The effects of various reaction conditions, including reaction time, temperature, enzyme loading, substrate molar ratio and water activity, were investigated. A Central Composite Rotatable Design was employed to search for the optimal conversion of (±)-menthol and enantiomeric excess. A quadratic polynomial regression model was used to analyze the experimental data at a 95% confidence level (p<0.05). The analysis confirmed that reaction temperature, enzyme loading and reaction time were the significant factors affecting the conversion of (±)-menthol. Moreover, reaction temperature, enzyme loading, substrate molar ratio and reaction time were found to affect the enantiomeric excess significantly. The coefficient of determination of these two models was found to be 0.980 and 0.967, respectively. Two sets of optimum reaction conditions were established and the verified experimental trials were performed for validating the optimum points. Under the optimum conditions, the conversion of (±)-menthol and the enantiomeric ratio exceeded 53% and 40%, respectively.

Direct Enantioselective HPLC Monitoring of Lipase-Catalyzed Kinetic Resolution of 2-Phenoxy Propionic Acid in Non-Standard Organic Solvents

In this work, a direct enantioselective HPLC monitoring system is developed. The system consists of an HPLC equipped with an immobilized cellulose-based chiral stationary phase Chiralpak IB, UV and a polarimetric detector in series. The developed system is used in the direct monitoring of the enantioselectivity of lipase-catalyzed enantioselective esterification of 2-phenoxy propionic acid of which the (R)-enantiomer is a precursor of the (R)-2-(p-hydroxyphenoxy)propionic acid known as an important intermediate in synthesizing aryloxyphenoxypropionic acid based agrochemicals. The versatility of the biocatalyzed reaction in chiral separation to access to both enantiomers of racemic 2-phenoxy propionic acid is demonstrated. The solvent versatility of the immobilized chiral stationary phase used in the direct monitoring of such reaction in non-standard HPLC solvent is shown.

Biocatalytic enantioconvergent separation of racemic mandelic acid

Chiral mandelate was produced by biocatalytic enantioconvergent separation of racemic mandelic acid. One pot enantioconvergent synthesis of ( R)-mandelic acid ester from racemic mandelic acid was achieved by a novel aqueous/organic two-phase system with two-enzyme process consisting of (1) lipase-catalyzed enantioselective esterification of racemic mandelic acid in organic solvent and (2) in situ racemization of unreacted isomer, ( S)-mandelic acid in aqueous phase by recombinant mandelate racemase. Lipase was screened from commercially available sources and mandelate racemase was prepared by overexpression of cloned gene originated from Pseudomonas putida in E. coli Top 10. Organic solvent was selected based on its effect on the partition characteristics for substrate and product, and enzymatic esterification and racemization. The aqueous/organic two-phase dynamic kinetic resolution (DKR) was attempted in a hollow-fiber membrane bioreactor wherein Candida antarctica lipase (CHIRAZYME L-2, Roche)-catalyzed enantioselective esterification and mandelate racemase-mediated racemization of unreacted mandelic acid were performed in ethylene dichloride and aqueous buffer, respectively. Using the novel DKR process, ( R)-mandelic ethyl ester was obtained from racemic mandelic acid in 65% isolated yield and 98%ee as the sole product.

Lipase-catalyzed enantioselective esterification of racemic ibuprofen coupled with pervaporation

Enantioselective esterification of racemic ibuprofen catalyzed by Candida rugosa lipase in isooctane was coupled with pervaporation of water by-produced by the reaction. A cross-linked poly(vinyl alcohol) (PVA) membrane and commercially available perfluorinated membranes (Nafion ® 117 and Nafion ® NE 450) were tested for selective removal of water from the reaction mixture. Effects of the reaction temperature, the concentration and nature of alcohol on the reaction rate and enantioselectivity were investigated systematically with and without pervaporation. The PVA pervaporation membrane appeared to be more suitable for the enantioselective esterification of ibuprofen than the Nafion ® membranes. The highest initial rate and enantiomeric ratio were obtained at an equimolar ratio of 1-octanol/1-decanol to racemic ibuprofen regardless of the application of pervaporation. Raising the reaction temperature from 30 to 60 °C increased the reaction rate, but decreased the enantiomeric ratio. However, in most cases, the concomitant pervaporation operation brought about the enhancement of the reaction rate and the enantiomeric ratio. This was thought to be due to the selective removal of excess water by pervaporation, leading to the reduction of undesirable effects on the enzymatic reaction by the excess water.

Comparison of lipase-catalyzed enantioselective esterification of (±)-menthol in ionic liquids and organic solvents

Enantioselective esterification of (±)-menthol was studied using Candida rugosa lipase (CRL) in ionic liquids (1-butyl-3-methyl-imidazolium hexafluorophosphate ([BMIM][PF 6]) and 1-butyl-3-methyl-imidazolium tetraflouroborate) and organic solvents of different hydrophobicities. Propionic anhydride was employed as an acylating agent. Because the enzyme showed comparable conversion yield and enantioselectivity in [BMIM][PF 6] and hexane in a 24-h reaction, more work focused on these two reaction media. Comparison of the activity, stability and enantioselectivity of CRL was carried out by examining the effects of the mole ratio of substrates, temperature, incubation time and enzyme recycling. It was found that temperature control was more crucial in the ionic liquid than in hexane to reach high conversion and enantioselectivity. The ionic liquid system showed an advantage of using less acid anhydride to achieve higher (±)-menthol conversion yield and better enantioselectivity. Moreover, during an incubation of 4–60 days in the ionic liquid, CRL activity was 2.5 times higher than its initial value, while that in hexane decreased to less than 60% in 2 days. In addition, the enzyme showed potentiality of recycled use in the ionic liquid. These advantages of the ionic liquid suggest that it would be used as a green alternative to organic solvents for the enantioselective esterification of (±)-menthol.

Resolution of (±)-menthol by immobilized Candida rugosa lipase on superparamagnetic nanoparticles

Lauric acid-stabilized magnetic particles were prepared by coprecipitation in the presence of lauric acid and used for the covalent immobilization of Candida rugosa lipase via carbodiimide activation. Size analysis by transmission electron microscopy (TEM) and measurement of magnetization curves revealed that the immobilized lipase was superparamagnetic. Resolution of (±)-menthol was performed by the immobilized lipase-catalyzed enantioselective esterification with propionic anhydride. Effects of various reaction parameters, such as enzyme load, solvents, water activity, substrate concentration, reaction time and temperature, on the conversion as well as enantioselectivity were investigated. As a result, (−)-menthyl propionate with a yield higher than 96% and over 88% enantiomeric excess of products was obtained. Better conversion and enantioselectivity could be expected for the immobilized lipase-catalyzed reaction performed at 30 °C for 2.5 h with 0.2 mol/l of (±)-menthol. Hexane was found to be the most suitable solvent, and the activity as well as enantioselectivity of the immobilized lipase decreased gradually with increasing water activity. Good durability of the immobilized lipase to catalyze the resolution of (±)-menthol was also observed.

Enhancement of enantioselectivity and reaction rate on the synthesis of (S)-ketoprofen hydroxyalkyl ester in organic solvents via isopropanol-dried immobilized lipase

Lipase-catalyzed enantioselective esterification between (R,S)-ketoprofen and alkanediol in organic solvents was developed to produce (S)-ketoprofen hydroxyalkyl esters. The acyl acceptor of 1,6-hexanediol for the resolution of (R,S)-ketoprofen yielded only the enantioselectivity (the enantiomeric ratio of initial rate for (S)-ketoprofen to that of (R)-ketoprofen) VS/VR = 8, when crude Lipase MY originating from Candida rugosa was used. However, isopropanol-dried immobilized lipases (IPA-dried IM-lipase) effectively enhanced the enantioselectivity to greater than 20 in the esterification of (R,S)-ketoprofen when 1,4-butanediol, 1,5-pentanediol or 1,6-hexanediol was employed. IPA-dried IM-lipase and isooctane were selected to use for optimally immobilized lipase and reaction medium, respectively. The IPA-dried IM-lipase exhibited the highest enantioselectivity, E = 26.7, to the (S)-enantiomer with 1,5-pentanediol and the best enzyme activity to the (S)-enantiomer with 1,4-butanediol. The finding indicates that the carbon chain length of the alkanediol strongly affected the enzyme activity and enantioselectivity of lipase-catalyzed esterification. A maximum enantioselectivity of 37 at 27 °C was generated by IPA-dried IM-lipase for the enantioselective esterification of racemic ketoprofen with 1,4-butanediol. IPA-dried IM-lipase can effectively increase the enantioselectivity of lipase. Copyright © 2005 Society of Chemical Industry

Lipase-catalyzed enantioselective esterification of mono-aza-benzo-15-crown-5-ether derivatives in organic media

For the purpose of developing a new chiral crown ether unit as a chiral synthon, three racemic mono azabenzo-15-crown-5-ethers, i.e. (R,S)-1-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-yl)-propan-2-ol, (R,S)-2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-yl)-1-phenyl-ethanol and (R , S)-1-[2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-ylmethyl)-phenyl]-ethanol were esterified with vinyl acetate using a lipase from Candida antarctica. The enzymatic acylation of alcohols produced monoacylated products. Two optically active azacrown ethers, (R)-propionic acid 1-methyl-2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-yl)-ethyl ester and (R)-acetic acid 1-[2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-ylmethyl)-phenyl]-ethyl ester were obtained within 48% and 36% yields, respectively and, at an enantiometric excess of over 99% in each case.

Lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol

The influences of water activity and solvent hydrophobicity on the kinetics of the lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol were investigated. The solvent effect was not similar for lipases from Candida rugosa (Crl), Mucor javanicus (Mjl), and porcine pancreas (Ppl). The lipase-catalyzed reaction rates in different solvents across a wide range of water activities revealed that the Ppl-catalyzed reaction exhibited no enantioselectivity and no substantial water activity or solvent dependence. The Mjl-catalyzed reaction proceeded faster, preferring the R-enantiomer reaction over that of its antipode, but had little solvent or water activity dependence. The Crl-catalyzed reactions in n-heptane and n-nonane had similar water activity dependence, but the reaction was considerably faster and more enantioselective (preferring the S-enantiomer reaction) in isooctane, a solvent whose hydrophobicity is intermediate between that of the other two alkanes. Substrate enantiomeric excess, for the Crl-catalyzed reaction at 96 hours and at a water activity of 0.65, in n-heptane, isooctane, and n-nonane was 40.9, 93.0, and 50.0%, respectively. Since the three solvents possess similar physical properties, the explanation for this anomalous behavior might be the effect of the solvent structural characteristics on Crl, since isooctane is the only branched alkane.

Lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol

The influences of water activity and solvent hydrophobicity on the kinetics of the lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol were investigated. The solvent effect was not similar for lipases from Candida rugosa (Crl), Mucor javanicus (Mjl), and porcine pancreas (Ppl). The lipase-catalyzed reaction rates in different solvents across a wide range of water activities revealed that the Ppl-catalyzed reaction exhibited no enantioselectivity and no substantial water activity or solvent dependence. The Mjl-catalyzed reaction proceeded faster, preferring the R-enantiomer reaction over that of its antipode, but had little solvent or water activity dependence. The Crl-catalyzed reactions in n-heptane and n-nonane had similar water activity dependence, but the reaction was considerably faster and more enantioselective (preferring the S-enantiomer reaction) in isooctane, a solvent whose hydrophobicity is intermediate between that of the other two alkanes. Substrate enantiomeric excess, for the Crl-catalyzed reaction at 96 hours and at a water activity of 0.65, in n-heptane, isooctane, and n-nonane was 40.9, 93.0, and 50.0%, respectively. Since the three solvents possess similar physical properties, the explanation for this anomalous behavior might be the effect of the solvent structural characteristics on Crl, since isooctane is the only branched alkane.