• 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.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1638-1640
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• 2006

A variety of chiral cyanohydrins were readily prepared from aldehydes with TMSCN under the influence of chiral titanium complex formed in situ from $Ti(O^iPr)_4$/TADDOL(I) in the presence of $Ph_3PO$ as additive. The double activation method produces trimethylsilylethers in excellent yield (95%) with moderate enantiomeric excess.

• Journal of Integrative Natural Science
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• v.8 no.2
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• pp.107-110
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• 2015

Amino acid-catalyzed directed asymmetric aldol reactions showed enhanced enantioselectivity when conducted in ionic liquids. Optically active products were afforded in better yields (up to 23% higher) and enantiomeric excess (up to 21% higher) in ionic liquids than in conventional organic solvents.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.369-374
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• 2006

$Rh-Pt/Al_{2}O_{3}$ catalysts were used for the first time to study its reaction characteristics in the asymmetric hydrogenation of ethyl pyruvate. The catalysts were prepared either by impregnation of Rh on a commercial $Pt/Al_{2}O_{3}$ or by sequential impregnation of Rh followed by impregnation of Pt on $Al_{2}O_{3}$. Reaction rate and enantiomeric excess (ee%) were compared according to the preparation method, Rh contents, and the reduction temperature of the catalyst. The physical characteristics of the catalysts were analyzed using XRD and TEM. Bimetallic $Rh-Pt/Al_{2}O_{3}$ catalysts showed an improved reaction rate and optical purity (63.6 ee%) with increasing the reduction temperature. The variation of the Rh contents as well as the preparation method elicited a big difference on the reaction rate, while enantiomeric excess (ee%) was lower (56~60%) with all bimetallic catalysts than with monometallic $Pt/Al_{2}O_{3}$ catalyst.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.491-496
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• 2008

The microsomal epoxide hydrolase gene (referred to as mMCEH) of Mugil cephalus was cloned by PCR, and then inserted to pColdI and pET-21b(+) vector, respectively. The recombinant E. coli possessing the recombinant plasmids exhibited the enantioperference toward (R)-styrene oxide. When enantioselective kinetic resolutions were conducted with 20 mM racemic styrene oxide, enantiopure (S)-styrene oxide was obtained with high enantiopurity more than 99% enantiomeric excess (ee) and 24.50% yield by using the recombinant E. coli harboring pET-21b(+)/mMCEH.

• 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.

• Journal of Microbiology and Biotechnology
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• v.30 no.2
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• pp.244-247
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• 2020

We have expressed extracellular poly(3-hydroxybutyrate) (PHB) depolymerase of Ralstonia pickettii T1 on the Escherichia coli surface using Pseudomonas OprF protein as a fusion partner by C-terminal deletion-fusion strategy. Surface display of depolymerase was confirmed by flow cytometry, immunofluorescence microscopy and whole cell hydrolase activity. For the application, depolymerase was used as an immobilized catalyst of enantioselective hydrolysis reaction for the first time. After 48 h, (R)-methyl mandelate was completely hydrolyzed, and (S)-mandelic acid was produced with over 99% enantiomeric excess. Our findings suggest that surface displayed depolymerase on E. coli can be used as an enantioselective biocatalyst.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.5
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• pp.306-308
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• 2003

Enantioselective hydrolysis for the production of chiral styrene oxide was investigated using the epoxide hydrolase activity of a newly isolated Rhodosporidium kratochvilovae SYU-08. The effects of reaction parameters - buffer type, pH, temperature, initial substrate concentrations, phenyl-1,2-ethanediol concentrations on hydrolysis rate, and enantioselectivity - were analyzed. Optically active (S)-styrene oxide with an enantiomeric excess higher than 99 % was obtained from its racemate. with a yield of 38 % (theoretically 50% maximum yield) from an initial concentration of 80 mM.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.65-68
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• 2003

The paper discusses the use of stable emulsion, prepared by membrane emulsification technology, to improve the enantiocatalytic performance of immobilised lipase in multiphasic membrane reactors. The production of optical pure (S)-naproxen from racemic naproxen methyl ester has been used as model reaction system. The enzyme was immobilised in the sponge layer (shell side) of capillary polyamide membrane with 50 kDa cut-off, The O/W emulsion, containing the substrate in the organic dispersed phase, was fed to the enzyme membrane reactor from shell-to-lumen. The results evidenced that lipase maintained stable activity during all the operation time (more than 250 hours), showing an enantiomeric excess (96 $\pm$2%) comparable to the free enzyme (98 $\pm$ 1%) and much higher compared to similar lipase-loaded membrane reactors used in two-separate phase systems (90%). The study showed that immobilised enzymes can achieve high stability as well as high catalytic activity and enantioselectivity.

• Applied Biological Chemistry
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• v.37 no.5
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• pp.397-401
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• 1994

Bioreduction with active dried baker's yeast proceeded smoothly in n-hexane, pentane or petroleum ether as an organic solvent system. Ethyl(1) and octyl 3-oxohexanoate(2) were reduced to $({\underline{R}})-ethyl(3)$ and $({\underline{S}})-octyl$ 3-hyroxy-hexanoate(4) with high enantiomeric excess, respectively.