• KSBB Journal
• /
• v.20 no.3
• /
• pp.133-141
• /
• 2005

This review presents the preparation, transport mechanism and application of molecularly imprinted membranes (MIM). Molecular imprinting has now been established as a technique which allows the creation of tailor-made binding sites for many classes of compounds. MIM have some advantages; a high capacity due to a large surface area, faster transport of substrate molecules and faster equilibrium of binding cavities compared to molecularly imprinted particles. MIM were prepared by covalent and non-covalent chemical bonding systems, by interactions between functional monomer and template. MIM can be prepared by in-situ polymerization, wet phase inversion, dry phase inversion, and surface imprinting method. MIM can continuously separate mixtures based on facilitated or retarded diffusion of the template. MIM can change their permeability in the presence of templates. MIM have a potential to be used to separate chiral compounds and materials with similar structures. However the application of MIM by the chemical industries is still in its infancy stages.

• Journal of the Korean Magnetic Resonance Society
• /
• v.19 no.1
• /
• pp.23-28
• /
• 2015

Four spiroketal sestertepenoids (1 ~ 4) were isolated from the marine sponge Haliclona species. Their planar structures were completely determined from a combination of extensive 1D and 2D NMR experiments, and also the relative stereochemistry on the chiral centers were established by the ROESY experiment. Compounds 1 ~ 3 were determined as the same planar structures with different stereochemistry on the chiral centers C-11 and C-13. Of these, 1 was identified as a new stereoisomer. Four compounds showed the inhibition effect of nitric oxide (NO) production in LPS-stimulated RAW 264.7 cells (0.7~2.0 g/ml).

• Korean Chemical Engineering Research
• /
• v.43 no.6
• /
• pp.647-661
• /
• 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
• /
• v.28 no.12
• /
• pp.2435-2441
• /
• 2007

The catalytic enantioselective electrophilic fluorinations of active methane compounds promoted chiral palladium complexes have been developed. Treatment of α-cyano acetates and α-cyanoalkylphosphonates with N-fluorobenzenesulfonimide as the fluorine source under mild reaction conditions afforded the corresponding α-cyano-α-fluorinated adducts in high yields with excellent enantiomeric excesses (up to 99% ee). These reactions can be conducted in alcoholic solvents without any precaution to exclude water and moisture.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.4
• /
• pp.829-836
• /
• 2009

The catalytic enantioselective electrophilic fluorinations of active methine compounds promoted chiral palladium complexes have been developed. Treatment of $\beta$-keto phosphonates and $\beta$-ketoesters with N-fluorobenzenesulfonimide as the fluorine source under mild reaction conditions afforded the corresponding $\alpha$-fluorinated adducts in high yields with excellent enantiomeric excesses (up to 99% ee). These reactions can be conducted in alcoholic solvents without any precaution to exclude water and moisture.

• Journal of Microbiology and Biotechnology
• /
• v.23 no.10
• /
• pp.1395-1402
• /
• 2013

Reductases convert some achiral ketone compounds into chiral alcohols, which are important materials for the synthesis of chiral drugs. The Saccharomyces cerevisiae reductase YOR120W converts ethyl-4-chloro-3-oxobutanoate (ECOB) enantioselectively into (R)-ethyl-4-chloro-3-hydroxybutanoate ((R)-ECHB), an intermediate of a pharmaceutical. As YOR120W requires NADPH as a cofactor for the reduction reaction, a cofactor recycling system using Bacillus subtilis glucose dehydrogenase was employed. Using this coupling reaction system, 100 mM ECOB was converted to (R)-ECHB. A homology modeling and site-directed mutagenesis experiment were performed to determine the NADPH-binding site of YOR120W. Four residues (Q29, K264, N267, and R270) were suggested by homology and docking modeling to interact directly with 2'-phosphate of NADPH. Among them, two positively charged residues (K264 and R270) were experimentally demonstrated to be necessary for NADPH 2'-phosphate binding. A mutant enzyme (Q29E) showed an enhanced enantiomeric excess value compared with that of the wild-type enzyme.

• Applied Chemistry for Engineering
• /
• v.17 no.6
• /
• pp.565-574
• /
• 2006

The trend towards the application of single enantiomers of chiral compounds is undoubtedly increasing. Among the various methods to obtain one single enantio-riched compound selectively, enantioselective catalysis is the most attractive method. Especially, it is important to increase the activity, selectivity and lifetime of usually expensive chiral catalysts with a minute quantity in the enantioselective synthesis. Immobilization of active homogeneous catalysts is a fashionable topic in asymmetric catalysis, providing the inherent advantage of easy separation and better handling properties. Many different ways have been investigated to improve the enantioselectivity of products and to recycle the catalysts. This review mainly focused on the present scope and limitations of different types of enantioselective heterogeneous catalysts.

• Food Science and Biotechnology
• /
• v.18 no.1
• /
• pp.18-24
• /
• 2009

The volatile compounds of dried sancho (Zanthoxylum schinifolium), an aromatic plant were extracted by simultaneous distillation and extraction (SDE) method and identified by gas chromatograph-mass spectrometry (GC-MS). Selected chiral constituents of sancho oil were characterized by enantiodifferentiation using multidimensional gas chromatograph (MDGC)-MS. A total of 57 compounds were identified and quantified, and the major compounds were identified estragole, nonanoic acid, octanoic acid, $\beta$-phellandrenene, and limonene. Among them, estragol (63.9%) was found as the predominantly abundant component of sancho. $\alpha$-pinene and nerolidol, and $\beta$-pinene and linalool were determined to be enantiomerically pure (100%) for their (S)-form and (R)-form, respectively. The enantiomeric composition of limonene in sancho revealed 83.9% purity for the (S)-enantiomer, whereas (E)- and (Z)-rose oxides showed mixtures of both enantiomers. The enantiomeric excess (%) for citronellal was 22.6% with the (R)-enantiomer as major enantiomer. The enantiomeric composition of these compounds can be used as parameter for authenticity control of sancho.

• Journal of the Korean Magnetic Resonance Society
• /
• v.18 no.2
• /
• pp.82-88
• /
• 2014

Three bicyclic and one monocyclic sesquiterpenoids were isolated from the marine sponge Topsentia species. Their planar structures were completely determined from a combination of extensive 1D and 2D NMR experiments, and also the relative stereochemistry on the chiral centers were established by the ROESY experiment. Compound 1 was determined as a new stereoisomer. Furthermore, the NMR spectral data for compounds 2 and 4, of which have not been reported, were listed. Four compounds did not show any cytotoxicity, instead compound 4 exhibited moderate antifungal activity against Candida albicans.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2431-2434
• /
• 2007

Potassium L-aspartate has been used as a catalyst for the cyanosilylation of carbonyl compounds producing corresponding cyanohydrin trimethylsilyl ethers in excellent yield of up to 98%. Although the catalyst is chiral, the enantioselectivities observed are generally poor except for one case, α-naphthaldehyde, 89% ee.