• KSBB Journal
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• v.20 no.4
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• pp.311-316
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• 2005

Epoxide hydrolases (EHs) are versatile biocatalysts for the preparation of chiral epoxides by enantioselective hydrolysis from racemic epoxides. Various microorganisms were identified to possess a EH activity by multiple sequence alignment and analysis of conserved domain sequence from genomic and megaplasmid sequence data. We successfully isolated Gordonia westfalica possessing EH activity from various microbial strains from culture type collections. G. westfalica exhibited (R)-styrene oxide preferred enantioselective hydrolysis activity. Chiral (S)-styrene oxide with high optical purity $(>\;99\%)\;ee)$ and yield of $36.5\%$ was obtained from its racemate using whole-cell of G. westfalica.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.330-336
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• 2007

In this study, new dinuclear chiral Co (salen) complexes bearing $BF_3$ have been synthesized and their properties as the asymmetric catalyst have been examined. The NMR, UV and ESCA analyses were performed to determine the structure of synthesized catalysts. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99 %ee). The dimeric structured chiral salen showed remakablely enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues, and in addition no racemization happened during the separation of product epoxides. The system described in this work is very efficient for the sinthesis of chiral epoxide and 1,2-diol intermediates.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.313-318
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• 2008

An enantioselective ring opening of racemic terminal epoxides has been achieved by using heterobimetallic cobalt salen complexes with variety of nucleophiles. They were proven to be highly enantioselective and reactive for the synthesis of valuable chiral building blocks in enantio-riched forms up to 98% ee.

• 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.

• Bulletin of the Korean Chemical Society
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• v.8 no.5
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• pp.421-423
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• 1987

The chiral B-isopinocampheyl-9-borabicyclo[3.3.1]nonane-potassium hydride (IPC-9-BBN-KH) and potassium B-isopinocampheyl-9-boratabicyclo[3.3.1]nonane (K IPC-9-BBNH) systems were applied to the enantioselective reduction of representative racemic epoxides, namely 1,2-epoxybutane, 1,2-epoxyoctane, 3,3-dimethyl-1,2-epoxybutane and styrene oxide. In the case of IPC-9-BBN-KH system, the optical yields are in the range of 8.3-37.4$\%$ ee. However, the system of K IPC-9-BBNH provides significantly lower optical yields, showing 7-22.5$\%$ ee. These results strongly suggest that the enantioselective coordination of chiral organoborane to the epoxy oxygen of racemic epoxides plays an important role in this resolution.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.593-596
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• 2000

Chiral epoxides are useful chiral synthons in organic synthesis and various biological methods have been investigated for the production of chiral epoxides. In this work, enantioselective resolution of racemic styrene oxide was investigated using an isolated Aspergillus niger sp. for the production of optically pure (S) -styrene oxide. The enantioselectivity and initial hydrolysis rates of racemic substrate were highly dependent on the pH, temperature, and the volume ratio of cosolvent. The experimental sets of pH, temperature, and the volume ratio of cosolvent were designed using central composite experimental design, and the reaction conditions were optimized using response surface analysis. The optimal conditions of pH, temperature, and the volume ration of cosolvent were determined to be 7.78, $28.32^{\circ}C$, and 2.4 %(v/v), respectively, and optically pure (S)-styrene oxide (> 99% ee) could be obtained with the 35 % yield by microbial enantioselective hydrolysis reaction.

• Korean Chemical Engineering Research
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• v.43 no.6
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• pp.647-661
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• 2005

The stereoselective synthesis of chiral terminal epoxide is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this review, we investigate the research and development trend in the asymmetric ring opening reactions using cobalt salen catalysts. Hydrolytic kinetic resolution (HKR) technology is the very prominent way to prepare optically pure terminal epoxides among available methods. We have synthesized homogeneous and heterogeneous chiral dinuclear salen complexes and demonstrated their catalytic activity and selectivity for the asymmetric ring opening of terminal epoxides with variety of nucleophiles and for asymmetric cyclization to prepare optically pure terminal epoxides in one step. The resolved ring opened product combined with ring closing in the presence of base and catalyst afforded the enantioriched terminal epoxides in quantitaive yield. Potentially, these catalysts are using on an industrial scale to produce chiral intermediates. The experimental results of HKR technology applied to the synthesis of various chiral compounds are presented in this paper.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2213-2218
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• 2012

Efficient synthetic routes were developed to prepare a sizable amount (4-15 grams) of the chiral epoxides 4-6 as versatile intermediates for the synthesis of aspartyl protease inhibitors of therapeutic interest such as HIV protease and ${\beta}$-secretase. Oxidative cleavage of the C(2)-C(3) double bond of L-ascorbic acid followed by functional group manipulation led to the preparation of the epoxide 10, which was opened with an azide to yield a common aziridine intermediate 12. Through opening of the aziridine ring of 12 with either a carbon or a sulfur nucleophile, chiral epoxide precursors 4-6 could be prepared for various HIV protease inhibitors. Except for the final low melting epoxides 5 and 6, all intermediates were obtained as crystalline solids, thus the synthetic pathway can be easily applied to a large-scale synthesis of the chiral epoxides.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.132-137
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• 2015

BEA-zeolite was modified by alkaline solution to introduce mesoporosity in the crystals and the homogeneous chiral Co(III) salen was immobilized in the mesopores. The dinuclear chiral Co(salen)-$GaCl_3$ catalyst immobilized on mesoporous BEA-zeolite showed high activity for the regioselective ring opening of terminal epoxides by carboxylic acids. Various chiral monoester derivatives could be synthesized with moderate enantioselectivity (47~69 ee%) from racemic epoxides through above reaction. When the chiral (S)-ECH was used as a reactant, it was efficiently resolved by carboxylic acid with a high enantioselectivity in the presence of heterogenized chiral salen catalyst, and the ring opened product afforded optically pure monoester epoxide (R)-GB (up to 98 ee%) through the ring closing in the basic solution by elimination of HCl. The heterogeneous catalyst could be fabricated easily, and the catalytic activity was retained for several times reuse without any further regeneration step.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.490-494
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• 2016

This paper describes the very efficient and highly enantioselective ring opening of terminal epoxides with alkyl and arene sulfonic acid. The dinuclear chiral (salen) Co complexes bearing Lewis acids of Al, Ga and In catalyze the reaction enantioselectively in the presence of tetrabutylammonium chloride using tert-butyl methyl ether as a solvent. The variation of the anion of the tetra butyl ammonium salt has significant impact on the reactivity and selectivity of the asymmetric ring opening of phenyl glycidyl ether with p-toluenesulfonic acid. The order of reactivity and selectivity was found to be $Cl^-$ > $l^-$ > $Br^-$ > $OH^-$. Strong synergistic effects of the different Lewis acid centers of Co-Al, Co-Ga and Co-In complexes were observed in the catalytic process. The dinuclear chiral salen catalyst containing $AlCl_3$ was found to be most active and highly enantioselective (91% ee).