• Bulletin of the Korean Chemical Society
• /
• v.31 no.3
• /
• pp.727-730
• /
• 2010

• Journal of the Korean Chemical Society
• /
• v.59 no.3
• /
• pp.205-208
• /
• 2015

• Bulletin of the Korean Chemical Society
• /
• v.35 no.1
• /
• pp.98-102
• /
• 2014

The organocatalytic enantioselective Michael addition reaction promoted by chiral binaphthyl-modified squaramide catalyst have been developed, allowing facile synthesis of the corresponding chiral 2-amino-4H-chromenes derivatives with excellent enantioselectivity (up to 99% ee). The method reported represents a practical entry for the preparation of chiral 2-amino-4H-chromenes derivatives.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.10
• /
• pp.1501-1502
• /
• 2005

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

• Journal of Life Science
• /
• v.15 no.5 s.72
• /
• pp.772-778
• /
• 2005

Chiral epoxides are important chiral synthons in organic synthesis for the production of chiral pharmaceuticals and functional food additives. Chiral epoxides can be synthesized by enantioselective introduction of oxygen to double bond of substrate by monooxygenase. Peroxidase also carry out asymmetric epoxidation of alkene in the presence of hydrogen peroxide. Kinetic resolution of racemic epoxides via enantioselective hydrolysis reaction by epoxide hydrolase (EH) is a very promising method since chiral epoxides with a high optical purity can be obtained from cheap and readily available racemic epoxides. In this review, various biocatalytic approaches for the production of chiral epoxides with several examples are presented and their commercial potential is discussed.

• KSBB Journal
• /
• v.17 no.4
• /
• pp.321-325
• /
• 2002

Chiral epoxides are valuable intermediates for the asymmetric synthesis of enantiopure bioactive compounds. Microbial epoxide hydrolases (EHs) are newly discovered enzymes and versatile biocatalysts for the preparation of chiral epoxides by enantioselective hydrolysis of cheap and easily available racemic epoxide substrates. EHs are commercially potential biocatalysts due to their characteristics such as high enantioselectivity, cofactor-independent catalysis, and easy-to-Prepare catalysts. In this Paper, recent progresses in biochemistry and molecular biology of EH and developments of novel reaction systems are reviewed to evaluate the commercial feasibility of EH-catalyzed hydrolytic kinetic resolution for the production of chiral epoxides.

• Journal of Microbiology and Biotechnology
• /
• v.24 no.7
• /
• pp.936-942
• /
• 2014

Using racemic (R,S)-2-(4-chlorophenyl)-3-methylbutyramide, an intermediate for the chiral pyrethroid insecticide Esfenvalerate, as a sole nitrogen source in a minimal medium, several strains with high enatioselectivity (${\geq}98%$) were isolated by enrichment techniques. One of the strains, LG 31-3, was identified as Burkholderia multivorans, based on physiological and morphological tests by a standardized Biolog station for carbon source utilization. A novel amidase was purified from B. mutivorans LG 31-3 and characterized. The enzyme exhibited (S)-selective amidase activity on racemic (R,S)-2-(4-chlorophenyl)-3-methylbutyramide. Addition of the racemic amide induced the production of the enantioselective amidase. The molecular mass of the amidase on SDS-PAGE analysis was shown to be 50 kDa. The purified amidase was subjected to proteolytic digestion with a modified trypsin. The N-terminal and internal amino acid sequences of the purified amidase showed a high sequence homology with those deduced from a gene named YP_366732.1 encoding indole acetimide hydrolase from Burkholderia sp. 383.

• Journal of Life Science
• /
• v.16 no.1
• /
• pp.168-174
• /
• 2006

Enantiopure epoxides are valuable intermediates for the asymmetric synthesis of enantiopure bioactive compounds. Microbial epoxide hydrolases (EHs) are versatile biocatalysts for the preparation of enantiopure epoxides by enantioselective hydrolysis of cheap and easily available racemic epoxide substrates. EHs are commercially potential biocatalysts due to their characteristics such as high enantioselectivity, cofactor-independent catalysis, and easy-to-prepare catalysts. In this paper, recent progresses In molecular engineering of EHs are reviewed to evaluate the commercial feasibility of EH-catalyzed hydrolytic kinetic resolution for the production of enantiopure epoxides.

• Archives of Pharmacal Research
• /
• v.23 no.3
• /
• pp.226-229
• /
• 2000

To obtain the standard compounds of metoprolol for a pharmacokinetic study, a convenient synthetic procedure to prepare enantiomers of metoprolol (3a) and its major metaboites, 2-4-(2-hydroxy-3-isopropylamino)propoxyphenylathanol (3b) and 4-(2-hydroxy-3- isopropylamino) pro-poxyphenylacetic acid (4), was developed from their respective starting materials, 4-(2-methoxyethyl)phenol (1a), 4-(2-hydroxyethyl)phenol (1b) and methyl 4-hydroxyphenylacetate (1c). These phenolic compounds (1a, b, c) were converted in situ to their corresponding phenoxides with sodium hydroxide treatment followed by (R)- or (S)-epichlorohydrin treatment. The resulting epoxides 2 were transformed to 3 through reaction with isopropylamine. Ester 3c was hydrolyzed to the metabolite 4. Measured using the HPLC method on chiral column without any derivatization, the optical purity of enantiomers of metoprolol and o-demethylated metabolite 3b ranged between 96-99 ％ ee and that of enantiomers of carboxylic acid metabolite 4 ranged 91％ ee.