• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.40-45
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• 2006

Electrical insulation is one of the most important parts in a high voltage apparatus. Traditionally mineral oils and synthetic esters have been widely used as dielectric coolants for power transformers. Recently, researchers are interested in the environmentally friendly vegetable oil from the environmental viewpoint. This paper reports on the synthesis and characterization of soybean based ester oils. Two different types of soybean based transformer oils, named as methyl ester and isopropyl ester were synthesized. The synthesis of these esters was achieved by transesterification reactions between soybean oil and alcohol in the presence of catalyst. The GC and NMR spectroscopic analysis of the esters have been performed. It was observed that isopropyl ester has better thermal resistance than methyl ester by TGA. Also, two esters have a good breakdown voltage and electrical resistance.

• 한국식품영양과학회지
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• 제23권3호
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• pp.496-501
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• 1994

The synthesis of lauryl palmitate from palmitic acid and lauryl alcohol was investigated in organic solvents using lipase. Water-immiscible organic solvent such as hexane, toluenem cyclohexane, and isooctane were found to be suitable of ester synthesis . The effect of water content on the initial rate of conversion was examined . As the content increased, the reaction rate increased. But addition of water in organic solvent decreased therostability of enzyme . The best lauryl palmitate synthesis was achieved with water content of 0.2-0.4% reaction temperature of 4$0^{\circ}C$ and 45$^{\circ}C$ for Candida cylindracea lipase porcine, pancreatic lipase, respectively. when ester synthesis was carried out under the optimum conditions, the conversion yield of palmitate into lauryl palmitate after 70hrs reached 85% and 69 % for the Candida cylindracea lipase and porcine opancreatic lipase, respectivley.

• Archives of Pharmacal Research
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• 제15권4호
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• pp.374-375
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• 1992

The marine sterol (22R, 23R)-methylenecholesterol 1 has been synthesized from readily available C-22 steroidal ester 2 utilizing an intermolecular acyclic ester enolate alkylation as the key step.

• Tribology and Lubricants
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• 제35권2호
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• pp.132-138
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• 2019

In this study, we demonstrate the effects of the acidic properties of montmorillonite (MMT), which is commonly used as a catalyst, on the conversion and selectivity of the dimer acid methyl ester (DAME) synthesis. We synthesize DAME by the dimerization of conjugated linoleic acid methyl ester (CLAME) and oleic acid methyl ester using MMT KSF. Incidentally, trimer acid methyl ester was formed as a by-product during the DAME synthesis. There is a necessity to adequately adjust the strength and quantity of the acid site to control the selectivity of DAME. Therefore, we vary the pH of the MMT acid by using various metal hydroxides. The purpose of this study is to increase the yield of monocyclic dimer acid methyl ester, which is a substance with adequate physical properties for industrial applications (e.g., lubricant and adhesive, etc.), using a heterogeneous catalyst. We report the dimerization of fatty acid methyl ester by using base treated-KSF, and apply it to conjugated soybean oil methyl ester. Then, we transmute the acid site properties of KSF, such as pH of 5 wt.% slurry KSF and various alkali metals (Li, Na, K, Ca). Characterization of base treated-KSF using a pH meter, x-ray diffraction, inductively coupled plasma-atomic emission spectrometer, Brunauer-Emmett-Teller surface analysis, and temperature-programmed desorption. We conduct an analysis of CLAME and DAME using nuclear magnetic resonance spectroscopy, gas chromatography, and gel permeation chromatography. Through these experiments, we demonstrate the effects of the acidic properties of KSF on the conversion and selectivity of the DAME synthesis, and evaluate its industrial potential by application to waste vegetable oil.

• Journal of Microbiology and Biotechnology
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• 제11권2호
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• pp.329-332
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• 2001

It has been known that, in enzymatic synthesis of cephalexin, the conversion yield was reduced by high loading of ampicillin acylase. In order to elucidate this phenomena, pH-controlled synthesis of cephalexin was examined using a purified Acetobacter turbidans acylase. When the pH of the reaction mixture was maintained at $6.20{\pm}0.04$, the reduction of the maximal conversion rate was not observed even with high enzyme loading. The kinetic parameters also suggest that pH drop during the enzymatic synthesis of cephalexin was mainly attributed to the rapid hydrolysis of D-${\alpha}$-phenylglycine methyl ester to D-${\alpha}$-phenylglycine, rather than the disappearance of 7-amino-3-deacetoxycephalosporanic acid for cephalexin synthesis. At higher molar ratio of two substrates, [D-${\alpha}$-phenylglycine methyl ester]/[7-amino-3-deacetoxycephalosporanic acid], the conversion rate was also elevated under pH-controlled enzymatic synthesis, which implies that the main reason for the pH drop is due to the production of D-${\alpha}$-phenylglycine methyl easter, the effect of a water-methanol cosolvent system on the ester, the effect of a water-methanol cosolvent system on the conversion profile was also examined. Even the though the conversion rate was increased in 10% methanol solution, a higher than 16% methanol in the reaction mixture caused an inactivation of enzyme.

• 공업화학
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• 제31권2호
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• pp.187-192
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• 2020

(2S,3R)-3-hydroxyhomoserine lactone (HSL)은 생리학적 활성을 가지는 다양한 종류의 화합물을 합성하기 위한 중간체로 활용되어 왔다. 본 논문에서는 OBO ester로 보호된 바이닐글라이신 유도체에 이중알콜화 반응을 수행하여 효율적인 HSL 합성 결과를 보고하고자 한다. 바이닐글라이신의 비고리 conformation은 크기가 큰 OBO ester에 의해 조절되었으며 N-inside conformation을 통해 이중알콜화 반응이 진행됨으로써 높은 anti 선택성(> 10 : 1)을 얻을 수 있었다. 이러한 결과를 바탕으로 N-Cbz-L-serine을 출발물질로 사용하여 총 7단계 34%의 수율로 HSL을 합성할 수 있었다. 본 연구의 결과는 amino diol 구조를 가지는 다양한 생리활성 천연물들의 입체선택적인 합성에 유용하게 활용될 수 있을 것으로 기대된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.244-245
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• 2005

Electrical insulation is one of the most important parts in a high voltage apparatus. Traditionally mineral oils and synthetic esters have been widely used as dielectric coolants for power transformers. Recently, researchers are interested in the environmental friendly vegetable oil from environmental viewpoint. This paper reports on the synthesis and characterization of soybean based ester oils. Two different types of soybean based transformer oils, named as methyl ester and isopropyl ester were synthesized. The synthesis of these esters was achieved by transesterification reactions of soybean oil and alcohol in the presence of catalyst. The GC and NMR spectroscopic analysis of the esters have been performed. The thermal stability of the esters was determined by thermal gravimetric analysis(TGA).

• Archives of Pharmacal Research
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• 제14권4호
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• pp.359-363
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• 1991

2,6-Dimethyl-4-(3'-nitrophenyl)1,4-dihydropyridine-3,5-dicarboxylic acid 5-(2'-cyanoethyl) ester 10a reacted with chloromethyl methylsulfide to give 2,6-dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid 3-methylthiomethyl 5-(2'-cyanoethyl) ester 11a in 88.1% yield. The synthesis of 2,6-dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3,5-dicrboxylic acid 3-methylthiomethyl ester 2a was achieved in 83% yield by alkaline hydrolysis of compound 11a in aqueous EtOH.

• Bulletin of the Korean Chemical Society
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• 제4권2호
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• pp.72-76
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• 1983

Cephaloglycin was synthesized directly from D-${\alpha}$ -phenylglycine methyl ester and 7-aminocephalosporanic acid using whole cell enzyme of Xanthomonas citri (IFO 3835). Some optimal conditions for cephaloglycin synthesis were investigated, and yield improvements for its production by several methods were attempted. Using the whole cell enzyme system, the reaction kinetic model for cephaloglycin synthesis is proposed, and the kinetic constants for D-${\alpha}$ -phenylglycine methyl ester hydrolysis, cephaloglycin synthesis, and cephaloglycin hydrolysis were determined. The $K_m$ values of D-${\alpha}$-phenylglycine methyl ester, 7-aminocephalosporanic acid, and cephaloglycin were 11 mM, 24 mM, and 167 mM, and $K_i$ value of D-${\alpha}$-phenylglycine was 15 mM, respectively. The pattern of product inhibition was found to be competitive one.

• 약학회지
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• 제33권2호
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• pp.80-86
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• 1989

2,6-Dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid 3-methyl 5-(2'-phenylsulfinyl) ethyl ester (10) or 2,6-Dimethyl-4-(2' or 3'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid 3-alkyl 5-(2-methylsulfonyl) ethyl ester (14a, b, c) were hydrolyzed by treatment with NaOH in aqueous EtOH solution to give 2,6-Dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid monomethyl ester (4b), 2,6-Dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid monomethyl ester (4c) and 2,6-Dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid monoisopropyl ester (4d) in 80 -90% yield. By the same procedure, 2,6-Dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid 3,5-bis (2'-methylsulfonyl) ethyl ester (15) gave 2,6-Dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid (4e) in 96% yield.