• KSBB Journal
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• v.14 no.3
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• pp.291-296
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• 1999

Chiral epoxides are key intermediates for the production of chiral pharmaceuticals, agrochemicals, and functional food additives. Chiral epoxides can be produced by either chemical or biological method. In biocatalytic production routes, chiral epoxides can be produced via epoxidations of prochiral alkenes by monooxygenase or peroxidase. Kinetic resolution of racemic epoxides using whole cells of bacteria or fungi might be commercially useful, since it is possible to obtain chiral epoxides with high optical purities from relatively cheap and readily avaiable racemic epoxides. Some bioprocesses already are commercially developed: the biocatalytic production of chiral epichlorohydrin via microbial stereospecific dehalogenation, and lipase-catalyzed enantioselective hydrolysis in a hollow fiber membrane bioreactor for the production of chiral methyl trans-3-(4-methoxyphenyl)glycidate. the intermediate for calcium antagonist diltiazem. The importance of biocatalytic production of chiral epoxides with several examples from literature are presented.

• KSBB Journal
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• v.17 no.6
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• pp.543-548
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• 2002

The enantioselective esterification of racemic ibuprofen catalyzed by a Candida rugosa lipase was studied according to reaction conditions such as a lipase concentration, reaction temperature, alcohol chain length and alcohol concentration. The S-(+)-ibuprofen alkyl esters prepared were converted to S-(+)-ibuprofen by hydrolysis with sulfuric acid as a catalyst. High conversions in the esterifications were obtained at 60$^{\circ}C$ and an equimolar ratio of octanol to ibuprofen. The initial reaction rate of the esterification decreased with increasing octanol concentration. Conversion and initial reaction rate increased with increasing alcohol chain length. Values of enantiomeric excess(ee) according to esterification reaction conditions did not change below 60$^{\circ}C$. On the other hand, values of conversion and ee for the chemical hydrolysis of S-(+)-ibuprofen alkyl esters were independent of alcohol alkyl chain length. Optical resolution of racemic ibuprofen was achieved by lipase catalyzed esterification and chemical hydrolysis. The separation method provided a high yield and enantioselectivity for the production of S-(+)-ibuprofen from racemic ibuprofen.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.769-776
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• 2008

The stereoselective synthesis of chiral terminal epoxide is of immense interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new chiral Co(salen) complexes bearing cobalt(II) chloride, iron(III) chloride and zinc(II) nitrate have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of terminal epoxides such as styrene oxide and phenylglycidylether by hydrolytic kinetic resolution technology and for the synthesis of glycidyl buthylate. The easily prepared complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (>99% ee). The newly synthesized chiral salen showed remakablely enhanced reactivity with substantially low loadings. The system described in this work is very efficient for the sinthesis of chiral epoxide and 1,2-diol intermediates.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.15-18
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• 1998

Membrane reactors are systems which combine a chemical reactor with a membrane separation process allowing to carry out simultaneously conversion and product separation. The catalyst can be immobilized on the membrane or simply compartmentalized in a reaction space by the membrane. Membrane reactors are today investigated to produce optically pure isomers and/or resolve racemic mixture of enantiomers. The interest towards these systems is due to the increasing demand of enantiomerically pure compounds to be used in the pharmaceutical, food, and agrochemical industries. In fact, enantiomers can have different biological activities, which often influence the efficacy or toxicity of the compound. On the basis of current literature there are basically two schemes on the use of membrane technology to produce enantiomers. In one case, the membrane itseft is intrinsically enantioselective: the membrane is the chiral system which selectively separates the wanted isomer on the basis of its conformation. In the other, a kinetic resolution using an enantiospecific biocatalyst is combined with a membrane separation process; the membrane separates the product from the substrate on the basis of their relative chemical properties (i.e. solubility). This kind of configuration is widely used to carry out kinetic resolutions of low water soluble substrams in biphasic membrane reactors [Giomo, 1995, 1997; Lopez, 1997]. These are systems where enzyme-loaded membranes promote reactions between two separate phases thanks to the properties of enzymes, such as lipases, to catalyse reactions at the org ic/aqueous interface; the two phases are maintained in contact and separated at the membrane level by operating at appropriate transmembrane pressure. A schematic representation of biphasic membrane reactor is shown in figure 1, while an example of enantiospecific reaction and product separation carried out with these systems is reported in figure 2.

• Analytical Science and Technology
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• v.34 no.4
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• pp.143-152
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• 2021

Capillary electrophoresis (CE) is an effective technique to study chiral recognition because it offers flexibility in adjusting vital factors. Currently, various available cyclodextrins (CDs) can be employed for the chiral separation of numerous analytes. Herein, we investigate the enantioseparation behavior of lipoic acid enantiomers in various types of single and dual CD systems through CE. Additionally, several impacted CE parameters were optimized through the systematic investigation based on the design of experiment (DoE) concept for a single system comprising a heptakis (2,3,6-tri-O-methyl)-β-CD and a dual system containing the combination of the single CD with a sulfated-β-CD. Consequently, absolute enantioresolution was obtained within 15 min on a common standard bare fused-silica capillary (64.5/56 cm in total/effective length, 50/365 ㎛ inner/outer diameter), maintained at 15 ℃ and at an applied voltage of 24 kV. The optimal background electrolyte consisted of 6 mM heptakis (2,3,6-tri-O-methyl)-β-CD dissolved in the solution of 58 mM borate buffer at pH 10. Furthermore, the results of apparent binding constant experiments indicated that the S-enantiomer-heptakis (2,3,6-tri-O-methyl)-β-CD complex exhibited a stronger affinity than its R-enantiomer counterpart. The obtained electrophoretic mobility values could be utilized to interpret the resolution achieved at various CD concentrations and the mobility behavior of the complexes elucidated the migration order of the enantiomers in an electropherogram.

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.365-370
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• 2019

In this study, effects of the ultrasonic irradiation during the reaction process were investigated for the enantioselective kinetic resolution (EKR) reaction of racemic epoxides in the presence of chiral cobalt salen catalysts, as compared to that of using the conventional mechanical stirring. In order to compare catalytic activities, the chiral cobalt salen complexes having $AlCl_3-$, $BF_3-$ and nitrobenzenesulfonic acid (NBSA) were synthesized and used as catalysts, and then three kinds of the racemic epoxides such as ephichlorohydrine (ECH), epoxy phenoxypropane (EPP) and propylene oxide (PO) were used as reactants. In addition, EKR reactions have been performed using the water and methanol as nucleophiles, respectively. The unique contribution of ultrasonic irradiation as a powerful mixing medium was evaluated in this study to improve the kinetics in comparison to the conventional mechanical agitation during EKR reactions. The reaction time to obtain the highest 99 ee% became shorten more than that of above 60%, when the ultrasonic irradiation was used. This result may be interpreted by the cavitation effect of ultrasound in the solution, generating a powerful shear force for the very violent mixing.