• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.49 no.2
• /
• pp.141-146
• /
• 2023

The efficient use of a chiral shift agent (3) containing bifunctional group (thiourea and tertiary amine) for the determination of the enantiomeric purity of racemic mixture (Hemiesters) has been studied. The diastereomeric complexes derived from a chiral shift agent (3) with various hemiesters gave rise to well separate signals of the methoxy protons of hemiesters. Good splitting signals for enantiomers of hemiesters in ¹H NMR are originated form the hydrogen bonds between carbonyl groups of hemiester and bifunctional groups of a chiral shift agent (3) such as thiourea moiety and tertiary amine. This study provides a quick and simple way to determine the chiral purity of hemiester using chiral transfer agent (3).

• Analytical Science and Technology
• /
• v.23 no.1
• /
• pp.97-101
• /
• 2010

(R)-N-3,5-dinitrobenzoyl (DNB) phenylglycinol derived chiral selector was used as a HPLC chiral stationary phase (CSP) for the resolution of racemic N-acylnaphthylalkylamines. In this study, determination of optical purity was performed by both chiral chromatography and NMR spectroscopy by using the (R)-phenylglycinol derived chiral selector. The data of accuracy and precision of each optical purity value are calculated from the results of NMR and HPLC experiments by comparing with true value. Average error of the NMR method was +2.2% with average RSD of 4.54%, while that of HPLC method was -3.5% with average RSD of 3.23%.

• Journal of the Korean Chemical Society
• /
• v.66 no.5
• /
• pp.420-423
• /
• 2022

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

• KSBB Journal
• /
• v.19 no.4
• /
• pp.263-268
• /
• 2004

The separation method using chiral stationary phase in preparation of chiral compound was wildly used, but in this work, supercritical fluid chromatography was suggested in the stability to resolve the chiral mixtures. To determine the optimum operating condition of the racemic ibuprofen, the retention factor and resolution with change in pressures, temperatures and the contents of IPA % (vol.) in CO$_2$ were investigated. The retention factor was decreased with increase in pressure and decrease in temperature. The factor was also influenced by the content of IPA in mobile phase, while the resolution was worse with a increase in IPA %. From the experimental results, the desirable separation condition was 130 bar, 311.15 K and 4% IPA in CO$_2$. Compared to the asymmetric peak shape by liquid chromatography, that of supercritical fluid chromatography was symmetric which was a favorable condition for preparative separation.

• 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.

• Applied Chemistry for Engineering
• /
• v.18 no.6
• /
• pp.630-635
• /
• 2007

New chiral Co-salen complexes with one $C_3-^tBu$ group in the structure have been synthesized and applied as a chiral catalyst. A dimeric chiral salen having aluminum group metal salts such as $AlCl_3$ displayed very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of epoxides to synthesize optically pure ${\alpha}$-aryloxy alcohols via phenolic kinetic resolution. The salen complexes immobilized on the inorganic support were also used as effective catalysts in that reaction. The identity of metal salts in the new chiral salen complex has proved to be important in the enantioselective reactions.

• Journal of the Korean Chemical Society
• /
• v.58 no.5
• /
• pp.456-462
• /
• 2014

Binary-doped conducting chiral polyaniline (PAni) was synthesized by electrochemical polymerization of aniline at low-temperature ($0^{\circ}C$) and room-temperature (RT) conditions. (+)-Camphorsulfonic acid (CSA) and hydrochloric acid (HCl) were used as a binary dopant. Formation of the binary-doped PAni rather than a mixture of the corresponding single-doped PAni was confirmed by cyclic voltammogram, FT-IR and circular dichroism spectra. The temperature influenced the electrochemical behavior and doping level, thus determining the crystallinity and morphology of the PAni. However, among other results, morphology of the PAni is found to be most strongly depends on the polymerization temperature. With increased temperature from the initial state to RT, morphology of the PAni changed from fibrous to short-fibrous structure. The sheet resistance of the PAni films on an ITO was measured by using four-point probe dc method.

• Applied Chemistry for Engineering
• /
• v.23 no.6
• /
• pp.577-582
• /
• 2012

In this work, vibrational circular dichroism (VCD) technique was applied for the determination of %EE of chiral compounds. It may provide an easy way to determine the %EE with a proper accuracy within 2% error ranges as well as the absolute configuration of enantiomers. We demonstrated herein a flow cell VCD (FT-VCD) technique for time-dependent %EE measurements. The simultaneous monitoring of the mole fraction and %EE for two chiral species (epichlorohydrin and glycidol mixture) in the mixture was shown to be successful without any further separation steps. Thus, we demonstrate that FT-VCD is an appropriate analytical tool to monitor the kinetics of reactions involving chiral molecules. FT-VCD also provides a convenient nondestructive approach for the time dependent determination of the optical purity of individual components in a reaction mixture containing chiral molecules.

• Journal of the Korean Chemical Society
• /
• v.33 no.4
• /
• pp.426-430
• /
• 1989

Amino alcohol-derived thiazolidinethiones [4-(S)-IPTT, 4(S)-ETT] serve as efficient chiral auxiliary in tin medicated aldol condensation. A highly enantioselective aldol-type reaction forming various ${\beta}$-hydroxy carbonyl compounds from 3-acetylthiazolidine-2-thione and achiral aldehyde is achieved via divalent tin enolate. The other advantages of these chiral auxiliaries were the ease of removal by methanolysis.