• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.47-50
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• 2008

The diastereoselectivity of Diels-Alder reactions were studied on the silica surface supported with different concentrations of cerium ion as efficient Lewis acid catalysts under solvent-free conditions. The results showed that the diastereoselectivity of reaction was highly improved in these conditions. The cerium ion was grafted on silica surface by using ion exchange method.

• Korean Journal of Environmental Agriculture
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• v.24 no.2
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• pp.164-168
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• 2005

An experimental design has been used to optimize the analysis of volatile component from fresh ginseng using solvent free solid injector (SFSI). The analysis were performed at three different sample preparing methods (fresh, oven drying and freezed drying), different injector port temperatures (100, 150, 200, 250 and $300^{\circ}C$) and different preheating time (3, 5, 7, 10 and 15 min) according to the above experimental design. The optimum conditions from analytical results were fresh sample (sample preparing methods), $250^{\circ}C$ (injector temperature) and 10 min (preheating time). Ginsengs grown for six years at Gumsan were prepared for fresh, white and red ginsengs. These fresh, white and red singsengs were analyzed for their volatile components by GC/MS equipped with SFSI according to the above the optimum conditions. A total of thirty-three volatile components were identified in fresh ginseng by SFSI, thirty-six in white ginseng and thirty-eight in red ginseng. These results suggested that the SFSI method could be used for isolating volatile component in ginsengs.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1625-1632
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• 2014

A concise and efficient one-pot synthesis of chroman-2,4-dione-based HKA derivatives by three component reaction of HKAs, triethoxymethane and 4-hydroxycoumarin derivatives under solvent-free and catalyst-free conditions is described. This protocol has many advantages, in that the GAP (Group-Assistant-Purification) chemistry process is involved in this method. As a result, the experimenter can avoid cumbersome process steps such as traditional chromatography and recrystallization purifications. The desired products can be easily obtained by washing the crude products with 95% EtOH.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.718-722
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• 2015

Techniques for immobilizing effective enzymes on nanoparticles for stabilization of the activity of free enzymes have been developing as a pharmaceutical field. In this study, we examined the effect of three different pH conditions of phosphate buffer, as a dissolving solvent for lysosomal enzymes, on the direct immobilization of lysosomal enzymes extracted from Hen's egg white and Saccharomyces cerevisiae. Titanium(IV) oxide (TiO₂) nanoparticles, which are extensively used in many research fields, were used in this study. The lysosomal enzymes immobilized on TiO₂ under each pH condition were evaluated to maintain the specific activity of lysosomal enzymes, so that we can determine the degree of melanin treatment in lysosomal enzymes immobilized on TiO₂. We found that the immobilization efficiency and melanin treatment activity in both lysosomal enzymes extracted from Hen's egg white and S. cerevisiae were the highest in an acidic condition of phosphate buffer (pH 4). However, the immobilization efficiency and melanin treatment activity were inversely proportional to the increase in pH under alkaline conditions. In addition, enhanced immobilization efficiency was shown in TiO₂ pretreated with a divalent, positively charged ion, Ca²⁺, and the melanin treatment activity of immobilized lysosomal enzymes on TiO₂ pretreated with Ca²⁺ was also increased. Therefore, this result suggests that the immobilization efficiency and melanin treatment activity of lysosomal enzymes can be enhanced according to the pH conditions of the dissolving solvent.

• Journal of the Korean Chemical Society
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• v.51 no.2
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• pp.115-124
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• 2007

A series of α, β-unsaturated ketones are synthesized by Crossed - Aldol condensation reaction, from ecofriendly 6-methoxy-2-naphthyl ketones and substituted benzaldehydes under solvent free conditions using silica-sulfuric acid as a catalytic reagent. The yields of ketones are more than 90% and the catalyst was reusable for further run. There is no appreciable decrease in the yield of product and the activity of catalyst. These chalcones were characterized by their physical constants and spectral data (IR, 1H-, 13C-NMR and Mass). These spectral data are subjected to correlate various Hammett substituent constants with single and multiparameter correlation equations. From the results of statistical analysis the influence of electronic effects of substituents on the spectral data of the ketones were explained.

• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.808-810
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• 2005

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1927-1930
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• 2010

A fast, efficient, and high yielding method for the preparation of amines by reductive amination of aldehydes and ketones using sodium borohydride in the presence of cellulose sulfuric acid in EtOH and under solvent-free conditions at room temperature is described.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3343-3347
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• 2011

A simple efficient and neat synthesis of ${\alpha}$-hydroxy phosphonates has been accomplished from aromatic/heterocyclic aldehydes and diethyl phosphite using $KHSO_4$ as a catalyst under solvent-free conditions at ambient temperature. These compounds are characterized by spectral and analytical data and tested for their anti-oxidant activity.

• Journal of the Korean Chemical Society
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• v.57 no.2
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• pp.169-171
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• 2013

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1209-1212
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• 2012

In spite of many reports in the literature concerning with oxidation of benzylic alcohols to carbonyl compounds with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in stoichiometric amounts or even more, we surprisingly found that benzylic alcohols are directly oxidized to oximes using a catalytic amount of DDQ in the presence of hydroxylamine hydrochloride under solvent-free conditions. The present tandem catalytic method can be efficiently used for preparation of oximes in the presence of some other functional groups with excellent chemoselectivity.