• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1863-1868
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• 2010

A simple and efficient synthesis of various $\alpha$-aminophosphonates (3a-l) by the reaction of substituted aromatic/heterocyclic aldehydes, 2-amino-6-methoxy-benzothiazole and dibutyl/diphenyl phosphites under microwave irradiation without catalyst was accomplished. The phosphonates were characterized by elemental analysis, IR, $^1H$, $^{13}C$- and $^{31}PNMR$ spectra. They showed promising antimicrobial, anti-oxidant activities depending on the nature of bioactive groups at the $\alpha$-carbon.

• Journal of the Korean Chemical Society
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• v.31 no.2
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• pp.153-161
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• 1987

The carcinogenicity of benzenoid hydrocarbons apparently depends strongly on the topological nature of the molecule. The existance of certain regions in the structure which are known propensity of benzenoid hydrocarbons to be carcinogenic. We try to identify the correlation between the number of potentially carcinogenic bay region in each of them and the quantity of Molecular Connectivity Index for 81 benzenoid hydrocarbons. Results indicate an excellent linear correlation between the number of bay region and the quantity of molecular connectivity index except the molecular containing single bond in their structure.

• Journal of the Korean Chemical Society
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• v.29 no.4
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• pp.356-364
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• 1985

Ab initio calculations with STO-3G method were carried out on isomers of isobutylene dianion and dilithioisobutylene, and geometry, energy and Mulliken population were discussed. Energy of reaction, ${\Delta}$E, for isodesmic processes involving these species and relative heats of formation, ${\Delta}H_f$, estimated with ${\Delta}$E have shown that the contribution of "Y-aromaticity" to the structural stabilization of Y-type dianion is a tenuous one but the alkylation appears to proceed via the Y-type dilithio compound.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.190-194
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• 2004

The structures and complexation energies of penta-O-tert-butyl ester 1 of p-tert-butylcalix[5]arene toward a series of alkyl ammonium guests have been optimized by ab initio HF/6-31G method. The calculated complexation efficiencies of 1 for alkyl ammonium guests have been found to be similar to the values of previously reported debutylated-calix[5]arene 2. Calculation results show that both of the calix[5]aryl derivatives have much better complexation ability toward ammonium cation without alkyl group over other alkyl ammonium guests. The structural characteristics of the calculated complexes are discussed as a function of the nature of the alkyl substituents of the ammonium guests.

• Natural Product Sciences
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• v.17 no.1
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• pp.10-13
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• 2011

As parts of our continuing search for biologically active compounds from medicinal plants, we investigated the constituents of the seeds of Amomum xanthioides and isolated a sesquiterpenoid, a nerolidol derivative from its MeOH extract. The chemical structure was determined by spectroscopic methods, including 1D and 2D NMR to be ($2S^*$,$2'R^*$,$5'S^*$)-2-(5'-ethenyltetrahydro-5'-methylfuran-2'-yl)-6-methylhept-5en-2-ol (1). Compound 1 was isolated for the first time from nature source. Compound 1 exhibited a good cytotoxicity against SK-OV-3 and SK-MEL-2 cells ($IC_{50}$: 16.7 and $8.6\;{\mu}M$, respectively) using a SRB bioassay. In this study, we also determined the absolute configuration of 2 reported in previous paper.

• Carbon letters
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• v.12 no.1
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• pp.39-43
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• 2011

Synthesis of carbon fibers from cotton fiber by pyrolysis process has been described. Synthesis parameters are optimized using Taguchi optimization technique. Synthesized carbon fibers are used for studying hydrogen adsorption capacity using Seivert's apparatus. Transmission electron microscopy analysis and X-ray diffraction of carbon fiber from cotton suggested it to be very transparent type material possessing graphitic nature. Carbon synthesized from cotton fibers under the conditions predicted by Taguchi optimization methodology (no treatment of cotton fiber prior to pyrolysis, temperature of pyrolysis $800^{\circ}C$, Argon as carrier gas and paralyzing time for 2 h) exhibited 7.32 wt% hydrogen adsorption capacity.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.281-281
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• 2006

In this study, the polyurethane which has versatile applications has been reinforced with the natural clay, hectorite. The hectorite has better properties than montmorillonite. There are studies on polyurethane and montmorillonite but polyurethane and hectorite composite is published first time. Polyurethane is industrial polyurethane which makes the study to be applicable to the industry. Exfoliated structure has been obtained without using organic modifiers due to the hydrophilic nature of the polymer matrix and the mineral clay. Mechanical properties have been improved as well.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1590-1600
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• 2014

Cinchona-based bifunctional catalysts have been extensively employed in the field of organocatalysis due to the incorporation of both hydrogen-bonding acceptors (quinuclidine) and hydrogen-bonding donors (e.g., alcohol, amide, (thio)urea and squaramide) in the molecule, which can simultaneously activate nucleophiles and electrophiles, respectively. Among them, cinchona-derived (thio)urea and squaramide catalysts have shown remarkable application potential by using their bifurcated hydrogen bonding donors in activating electrophilic carbonyls and imines. However, due to their bifunctional nature, they tend to aggregate via inter- and intramolecular acid-base interactions under certain conditions, which can lead to a decrease in the enantioselectivity of the reaction. To overcome this self-aggregation problem of bifunctional organocatalysts, we have successfully developed a series of sulfonamide-based organocatalysts, which do not aggregate under conventional reaction conditions. Herein, we summarize the recent applications of our cinchona-derived sulfonamide organocatalysts in highly enantioselective methanolytic desymmetrization and decarboxylative aldol reactions. Immobilization of sulfonamide-based catalysts onto solid supports allowed for unprecedented practical applications in the synthesis of valuable bioactive synthons with excellent enantioselectivities.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.881-885
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• 2014

Photophysics of 10-hydroxybenzo[h]quinoline (HBQ) has been in controversy, in particular, on the nature of the electronic states before and after the excited state intramolecular proton transfer (ESIPT), even though the dynamics and mechanism of the ESIPT have been well established. We report highly time resolved fluorescence spectra over the full emission frequency regions of the enol and keto isomers and the anisotropy in time domain to determine the accurate rates of the population decay, spectral relaxation and anisotropy decay of the keto isomer. We have shown that the ~300 fs component observed frequently in ESIPT dynamics arises from the $S_2{\rightarrow}S_1$ internal conversion in the reaction product keto isomer and that the ESIPT occurs from the enol isomer in $S_1$ state to the keto isomer in $S_2$ state.

• Fibers and Polymers
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• v.5 no.1
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• pp.52-58
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• 2004

Previous investigation results revealed that after the Low Temperature Plasma (LTP) treatment, the hydrophilicity of wool fiber was improved significantly. Such improvement enhances the wool dyeing and finishing processes which might be due to the changes of the wool surface to a more reactive one. In this paper, wool fibers were treated with LTP with different gases, namely, oxygen, nitrogen and gas mixture (25 % hydrogen/75 % nitrogen). Investigations showed that chemical composition of wool fiber surface varied differently with the different plasma gas used. The surface chemical composition of the different LTP-treated wool fibers was evaluated with different characterization methods, namely FTIR-ATR, XPS and saturated adsorption value. The experimental results were thoroughly discussed.