• Journal of Microbiology and Biotechnology
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• v.14 no.1
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• pp.97-104
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• 2004

Water-sludge bacteria were screened to find a lipase enantioselectively hydrolyzing itraconazole precursor, which is well known as the starting material of antifungal drug agents. A bacterial strain was isolated and identified as Acinetobacter junii SY-01. After the strain was cultivated, the enzyme was purified 39.4-fold using ultrafiltration and gel filtration through a Sephadex G-100 chromatographic column and the activity yield was 34.9%. The molecular weight of the enzyme was about 40 kDa, as measured by SDS-PAGE, and the optimum pH was 7.0- 9.0 and stable at pH 6.0- 9.0. The optimum temperature was 45- $5^{\circ}C$, and 73% of the enzymes activity remained after incubation at 70% for 1 h. Enzyme activity was enhanced by gall powder, sodium deoxycholate, a cationic detergent Tween 80, and a non-ionic detergent Triton X-100, but was markedly inhibited by metal ions such as $Hg^{2＋},Cu^{2＋},Ni^{2＋}/,Ca^{2＋}$, and an anionic-surfactant sodium dodecylsulfate. The $K_{m}$ values for (R)- and (S)-enantiomers of the itraconazole precursor were 0.385 and 21.83 mM, respectively, and the $V_{max} values ($\mu$Mㆍmin^{-1}.)$ were 6.73 and 6.49, respectively. The acetyl group among the different acyl moieties of itraconazole precursor showed the highest enantioselectivity for the hydrolysis by the Acinetobacter junii SY-01 lipase, and the lipase from Acinetobacter junii SY-01 displayed better enantioselectivity than that of commercially available lipases and esterases.

• 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.

• 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.31 no.3
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• pp.635-638
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• 2010

As a new strategy for the optimization of a chiral catalyst, the catalytic activity of the host-guest complexes of chiral bisphosphine bearing imidazolidinone was investigated in Rh-catalyzed asymmetric hydrogenation of enamide. Marginal enhancement in enantioselectivity was observed and the nature of interaction between host-guest was experimentally elucidated.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.2960-2964
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• 2011

The efficient asymmetric hydrosilylation of imines in the presence of polymethylhydrosiloxane has been investigated by screening chiral diamine-zinc complexes. A series of chiral diamine ligands were prepared from optically pure 1,2-diphenyl-1,2-ethanediamine and screened for effectiveness. N-Benzylic substituents were required for high enantioselectivity; ligands with bulky groups or extra coordinating groups such as OH and S lowered the catalytic activity. The level of asymmetric induction was usually in >90% ee range for aromatic imine substrates. A linear correlation between the ee of the ligand and that of the product was observed, indicating the presence of a 1:1 ratio of ligand to metal coordination in the active catalytic complex.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.804-807
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• 1999

New copper complexes with a ligand, L(L=N,N'-cyclohexane bis(ferrocenylmethylene)amine) which was obtained from ferrocene carboxaldehyde and 1,2-diaminocyclohexane with a mole ratio of 2:1, were prepared and characterized. Those were adapted to asymmetric catalysis. The copper(II) complexes do not work in cyclopropanation of styrene and ethyl diazoacetate but copper(I) complex catalyzes. The Cu(I)LOTf (OTf=trifluorometanesulfonate) shows a good regioselectivity giving high trans to cis ratio of up to 80:20.

• Proceedings of the Korean Society of Life Science Conference
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• 2001.11a
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• pp.21-28
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• 2001

A newly isolated Aspergillus niger possessing the novel epoxide hydrolase(EHase) activity was investigated for the enantioselective hydrolysis of racemic aromatic epoxides. The gene encoding EHase was cloned by RT-PCR, and molecular characteristics of the EHase gene were compared with other microbial EHases. The cloned gene encodes 398 amino acids with a deduced molecular mass of 44.5 kDa and pI of 4.83, and sequence homology with other microbial EHase was low. Functional recombinant EHase could be obtained by heterologous expressions in E. coli. Enantioselectivity of recombinant EHase was tested for valuable aromatic epoxide intermediates. Reaction conditions of EHase-catalyzed asymmetric resolution were optimized for the production of chiral styrene oxide.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.167-179
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• 2005

Chiral epoxides are highly valuable intermediates, used for the synthesis of pharmaceutical drugs and agrochemicals. They have broad scope of market demand because of their applications. A major challenge in modern organic chemistry is to generate such compounds in high yields, with high stereo- and regio-selectivities. Epoxide hydrolases (EH) are promising biocatalysts for the preparation of chiral epoxides and vicinal diols. They exhibit high enantioselectivity for their substrates, and can be effectively used in the resolution of racemic epoxides through enantioselective hydrolysis. The selective hydrolysis of a racemic epoxide can produce both the corresponding diols and the unreacted epoxides with high enantiomeric excess (ee) value. The potential of microbial EH to produce chiral epoxides and vicinal diol has prompted researchers to explore their use in the synthesis of epoxides and diols with high ee values.

• KSBB Journal
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• v.15 no.3
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• pp.313-317
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• 2000

In this paper enantioselective production of levofloxacin by porcine liver esterase was investigated, To enhance the produc0-tivity various factors which affect the enzyme activity and the enantioselectivity were optimized, In terms of temperature and pH 45$^{\circ}C$ and 4.8 were found to be the best conditions for enzyme reaction. Addition of ofloxacin butyl ester the substrate at the concentration of 5 g/L was desirable to avoid the product inhibition and the activity of porcine liver esterase was maintained up to 72 hours.In addition to enhance the availability of substrate effect of solvent was also examined. It was found that the application of 5% (v/v) of acetone acetonitrile and dimethylsulfoxide did not increase the conversion of substrate and the presence of 5%(v/v) butanol inhibited the enzyme activity significantly.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.4
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• pp.282-287
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• 2006

A Caulobacter crescentus epoxide hydrolase(CCEH) from a recombinant Escherichia coli was purified to homogeneity using a three-step procedure. The CCEH protein was purified 7.3-fold with a 22.9% yield in overalll activity. The optimal reaction temperature and pH were determined to be $37^{\circ}C$ and pH 8.0, respectively. The addition of 10%(v/v) dimethylsulfoxide as a cosolvent improved the enantioselectivity of CCEH for a batch kinetic resolution of racemic indene oxide.