• Title/Summary/Keyword: 하이드록시에스터

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Synthesis and Characteristics of Hydxoxypropyl Celluloses Containing Cholesteryl and Acryloyl Groups (콜레스테릴과 아크릴로일 그룹을 지닌 하이드록시프로필 셀룰로오스들의 합성 및 특성)

  • 김장훈;정승용;마영대
    • Polymer(Korea)
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    • v.28 no.1
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    • pp.92-102
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    • 2004
  • (6-Cholesteryloxycarbonylpentoxypropyl)celluloses (CHPCs) with degree of esterification (DE) ranging from 2.25 to 2.91 were synthesized by reacting hydroxypropyl cellulose with 6-cholesteryloxycarbonylpentanoyl chloride. The acrylic esters of CHPCs (CHPCEs) and their photocrosslinked films with liquidcrystalline order were also synthesized. The thermotropic properties of mesophase for both uncrosslinked and crosslinked samples and the swelling behavior of the crosslinked samples in acetone were investigated. The hydroxypropyl cellulose exhibited an enantiotropic cholesteric phas, while all the uncrosslinked cholesterylbearing samples exhibited a monotropic cholesteric phases; the 6-cholesteryloxycarbonylpentanoyl chloride also showed a monotropic smectic phase. The hydroxypropyl cellulose formed a right-handed helix whose optical pitch (λ$\sub$m/) increases with temperature, whereas all the uncrosslinked derivatives farmed left-handed helices whose λ$\sub$m/'s decreased with temperature. The thermal stability of the mesophase and the magnitude of λ$\sub$m/ at the same temperature for both CHPCs and CHPCEs decreased with increasing DE. All the crosslinked samples, in constrast with CHPCEs, did not display reflection colors but exhibited an anisotropic swelling characteristic of crosslinked gel retaining liquid-crystalline order.

Thermotropic Behavior of Hydroxypropyl Chitosans Bearing Cholesteryl and Acryloyl Groups (콜레스테릴과 아크릴로일 그룹을 지닌 하이드록시프로필 키토산들의 열방성 거동)

  • 김장훈;정승용;마영대
    • Polymer(Korea)
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    • v.28 no.1
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    • pp.41-50
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    • 2004
  • A new hydroxypropyl chitosan capable of forming a thermotropic liquid crystalline phase and two kinds of derivatives based on the hydroxypropyl chitosan (6-cholesteryloxycarbonylpentoxypropyl) chitosans (CHPCTs) and acrylic acid esters of CHPCT (CHPCTEs) were synthesized. The crosslinked films with liquid crystalline order were also prepared by photocrosslinking CHPCTE in mesophase. The liquid crystalline properties for all the samples and the swelling behavior of the crosslinked samples in acetone were investigated. In contrast with the hydroxypropyl chitosan, all the uncrosslinked cholesteryl-bearing samples farmed monotropic cholesteric phases with left-handed helicoidal structures and exhibited reflection colors over the full cholesteric range. This is the first report of a thermotropic cholesteric liquid crystalline chitosan derivative with reflection bands in the visible region. Both the optical pitches (λ$\_$m/'S) of CHPCT and CHPCTE decrease with temperature or with cholesteryl content at a given temperature. However, the λ$\_$m/ of CHPCT was larger than that of CHPCTE at the same temperature and at the same cholesteryl content. All the crosslinked samples did not display reflection colors, indicating that the cholesteric structure of CHPCTE significantly changes upon crosslinking. The two-dimentional anisotropic swelling characteristic of liquid crystalline networks was observed for all the crosslinked samples.

Synthesis and Properties of Photocurable Epoxy Modified Acrylates Using Half-Ester Acrylates (하프-에스터 아크릴레이트를 이용한 광경화형 에폭시 변성 아크렐레이트의 합성과 물성)

  • 김동국;임진규;김우근;허정림
    • Polymer(Korea)
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    • v.28 no.6
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    • pp.531-537
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    • 2004
  • Various half-ester acrylates were prepared from anhydrides and 2-hydroxyethyl acrylate. Photocurable epoxy modified acrylates were prepared from synthesized half-ester acrylate and neopentylglycol diglycidylether. Physical properties such as hardness, yellowing, tensile strength and elongation were tested and compared as the structure of oligomer in cured-film differs. It was found that viscosity of neopentylglycol diglycidylether-hexahydrophthalic anhydride (NP-HA) was highest. Hardness and tensile strength of photocrosslinked neopentylglycol diglycidylether-hexahydrophthalic anhydride were better than those of other photocrosslinted epoxy acrylates. And 5% weight loss temperature of photocrosslinked neopentylglycol diglycidylether-hexahydrophthalic anhydride was higher than those of other photocrosslinked epoxy acrylates. Value of yellow index of photocrosslinked neopentylglycol diglycidyl ether-succinic anhydride (NP-SA) was lower than the other products.

Efficient Stereoselective Synthesis of (2S,3S,4S)-3,4-Dihydroxyglutamic Acid ((2S,3S,4S)-3,4-다이하이드록시글루타믹산의 효율적인 입체선택적 합성)

  • Jeon, Jongho;Shin, Nara;Lee, Jong Hyup;Kim, Young Gyu
    • Applied Chemistry for Engineering
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    • v.25 no.4
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    • pp.392-395
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    • 2014
  • (2S,3S,4S)-3,4-Dihydroxyglutamic acid (DHGA), a biologically active ${\alpha},{\beta}$-dihydroxy-${\gamma}$-amino acid, was efficiently synthesized from a readily available D-serine derivative in 30% overall yield over 11 steps. The key stereoselective $OsO_4$-catalyzed dihydroxylation reaction controlled by an N-diphenylmethylene group on the amino group of ${\gamma}$-amino-${\alpha},{\beta}$-unsaturated (Z)-ester successfully introduced the diol moiety of the intermediate 5a in 86% with more than 10 : 1 diastereomeric ration. Then it was in turn successfully converted to the desired target compound, (2S,3S,4S)-3,4-DHGA, via simple oxidation and hydrolysis in a highly stereoselective manner and a higher yield than the previous syntheses. This result strongly supports that our synthetic methodology of stereoselective $OsO_4$-catalyzed dihydroxylation should be useful in stereoselctive synthesis of various bioactive compounds with an amino diol moiety.

Synthesis of Highly Enantiomerically Enriched Arenesulfonic Acid 2-Hydroxy Esters via Kinetic Resolution of Terminal Epoxides (속도론적 분할법을 통한 말단 에폭사이드로부터 고광학순도의 아렌술폰산 2-하이드록시 에스터의 합성)

  • Lee, Yae Won;Yang, Hee Chun;Kim, Geon-Joong
    • Applied Chemistry for Engineering
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    • v.27 no.5
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    • pp.490-494
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    • 2016
  • This paper describes the very efficient and highly enantioselective ring opening of terminal epoxides with alkyl and arene sulfonic acid. The dinuclear chiral (salen) Co complexes bearing Lewis acids of Al, Ga and In catalyze the reaction enantioselectively in the presence of tetrabutylammonium chloride using tert-butyl methyl ether as a solvent. The variation of the anion of the tetra butyl ammonium salt has significant impact on the reactivity and selectivity of the asymmetric ring opening of phenyl glycidyl ether with p-toluenesulfonic acid. The order of reactivity and selectivity was found to be $Cl^-$ > $l^-$ > $Br^-$ > $OH^-$. Strong synergistic effects of the different Lewis acid centers of Co-Al, Co-Ga and Co-In complexes were observed in the catalytic process. The dinuclear chiral salen catalyst containing $AlCl_3$ was found to be most active and highly enantioselective (91% ee).