• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1998년도 가을 학술발표회논문집
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• pp.94-97
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• 1998

We have been studying :he synthesis of thermotropic polyurethanes, based on structural modifications by means of (i) the introduction of bulky substituent group in the aromatic ring to decrease the degree of lateral packing, (ii) the copolymerization of two kinds of monomers having different alkylene lengths to lower the regularity of the polymer structure, and (iii) the use of nonlinear monomers to lower the persistence length of the polymer chain in the liquid crystalline phase and to decrease the lateral interactions in the solid state. (omitted)

• 한국자기공명학회논문지
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• 제2권1호
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• pp.50-58
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• 1998

The systematic chirality investigations were made on the basic of the fact that zinc-binding tallysomycin (ZnTLMA) could have chiral centers (Zn, NC3, C6) at possible 4-, 5-, and 6-coordination models. Although our NMR data exhibit that the ligation sites are ${\beta}$-aminoalanine, ${\beta}$-hydroxyhistidine, and pyrimidine moiety, all possible coordination modes were tested out to see what kind of chiralities on NC3-C6 are favorable to each coordination mode. Tests were also made that take into account the specific configuration of functional groups, including ${\beta}$-aminoalanine, sugar ring, and ${\beta}$-hydroxyhistidine. Tests were finally extended to zinc-water binding and specific conformational studies by introducing various hydrogen bonding networks associated with the propionamide side chain and the carbamide group of mannose. Results of systematic chirality investigations exhibit that the S-S configuration of NC3-C6 is favorable to all of coordination models, but the R-S configuration, if exists at all, should have internal strain on C6 chiral center.

• 대한화학회지
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• 제33권3호
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• pp.321-325
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• 1989

해양 생물에는 육지 생물에 비해 훨씬 다양하고 특이한 구조의 sterol이 나타나고 있으며 이런 특질들은 화학자들에게 여러가지 흥미있는 생화학적 혹은 유기화학적인 관심을 불러 일으며 왔다. 본 연구에서는 한국산 청각(Codium fragile)으로부터 3개의 sterol 성분을 분리 확인하였다. 주 sterol 성분은 탄소가 29인 clerosterol 였으며 codisterol과 cholesterol도 소량 발견되었다.

• Archives of Pharmacal Research
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• 제28권2호
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• pp.129-141
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• 2005

(-)-Fumagillol (1), a hydrolysis product of fumagillin, has been synthesized by several group from commercially available 1,2:5,6-di-O-isopropylidene-${\alpha}$-D-allofuranose in a highly stereoselective manner. Chiral centers on C5 and C6 came from D-allofuranose and the asymmetric center on C4 was accomplished by 1,3-chirality transfer using the Claisen rearrangement on a chiral allyl alcohol. Chirality, which is necessary on an epoxide consisting of the spiro-ring system, was diastereoselectively constructed by the well-known reaction, intramolecular ester enolate alkylation (IEEA), which showed that this reaction can be applied to the alpha-alkoxy ester system. The epoxide on the side chain was regioselectively introduced by the difference between the number of substituents on the vinyl groups. This accomplishment proved that IEEA can be a useful tool for the synthesis of complex molecules.

• 약학회지
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• 제39권3호
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• pp.329-336
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• 1995

Conformational free energy calculations using an empirical potential function and a hydration shell model(program CONBIO) were carried out on hypoglycemic agent acetohexamide and tolazamide in the unhydrated and hydrated states. The initial geometry of sulfonylureas was obtained from X-ray crystallographieal data and homologous molecular fragments. In both states, the feasible conformations were obtained from the calculations of conformational energy, conformational entropy, and hydration free energy by varying all the torsion angles of the molecules. From the calculation results, it is known that the conformations] entropy is the major contribution to stabflize the low-free-energy conformations of two sulfonylureas in both states. But, in hydrated state, the hydration does not directly affect each conformations. The intramolecular hydrogen bonding of sulfonylurea hydrogen and 7-membered nitrogen appeared to the conformations of tolazamide in both states. It is thought that the hydrogen bonding decrease steric hindrance on the receptor binding direction. The substitution of alicyclic or N-heterocyclic ring than that of carbons chain of urea moiety may be properly interaction between sulfonylureas and the putative pancreatic receptor.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2854-2860
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• 2010

Synthesis of a new series of pyrimidinyl-imidazo[2,1-b]thiazole derivatives is described. Their antiproliferative activity against A375 human melanoma cell line was tested and the effect of substituents on the pyrimidinyl ring side chain was investigated. The biological results indicated that most of the newly synthesized compounds showed moderate activity against A375, compared with Sorafenib. Among all of these derivatives, the cyclic sulfamide derivatives IIIa, IIIb, and IIIe showed the most potent antiproliferative activity against A375 human melanoma cell line. The IC50 values of compounds IIIa,b were in nanomolar scale. In addition, compound IIIe ($IC_{50}=1.9\;{\mu}M$) also demonstrated more potent antiproliferative activity compared with Sorafenib ($IC_{50}=5.6\;{\mu}M$).

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1305-1307
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• 2009

We have investigated the new modification of poly (vinyl phenol) (PVP) for low hysteresis organic thin film transistors (OTFTs). In order to suppression of hysteresis phenomenon, synthesized various backbone structure polymeric gate dielectric. The modified polymeric dielectric was synthesized by inducing ringshape phenol backbone structure instead of conventional chain. We could be observed that relieved hysteresis and excellent air stability from ring-shape phenol backbone structure.

• Elastomers and Composites
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• 제50권3호
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• pp.175-183
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• 2015

A series of fluorinated aromatic poly(hydroxyamide)s (PHAs) were synthesized by direct polycondensation of diacides containing 2,6-dimethylphenoxy group and quinoxaline ring in the main chain with 2,2-bis-(3-amino-4-hydroxyphenyl) hexafluoropropane. The PHAs had relatively low inherent viscosities in the range of 0.35~0.43 dL/g at $35^{\circ}C$ in DMAc solution. All PHAs exhibited excellent solubility in aprotic solvents such as NMP, DMAc, DMF and DMSO as well as in common organic solvents such as pyridine, THF, and m-cresol at room temperature. However, the poly(benzoxazole)s (PBOs) were quite insoluble in all organic solvents except partially soluble in concentrated sulfuric acid. The PBOs showed glass transition temperatures between 233 and $284^{\circ}C$ by DSC and maximum weight loss temperatures in the range of $536-546^{\circ}C$ by TGA.

• Macromolecular Research
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• 제13권4호
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• pp.321-326
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• 2005

Photochromic diarylethene polymers (DPs) in which 1,2-bis(2-methylbenzo[b ]thiophene-3-yl)hexafluorocyclopentene (BTF6) were covalently grafted onto the polymer main chain as pendant photochromic units were newly synthesized and their photochromic properties were investigated using steady-state and picosecond timeresolved spectroscopies. Polysiloxanes substituted with BTF6 molecules were prepared by sol-gel process using a mixture of tetraethoxysilane (TEOS), a silylated BTF6, and an organically modified silane precursor in the presence of HCl. The polysiloxane film (DP1) prepared from $\omega-methoxy$ poly(ethylene glycol) 3-(triethoxysilyl) propylcarbainate (MPGSC) as the silane precursor showed a much lower glass transition temperature than that (DP2) from heptadecafluorodecyltrimethoxysilane (HDFTMS). The ring-closure quantum yields of DP1 and DP2 were determined to be 0.20 and 0.02, respectively. Such a large difference in the quantum yield was attributed to the polymer matrix environment of the free inner volume.

• Archives of Pharmacal Research
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• 제24권4호
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• pp.300-306
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• 2001

A novel and two known bioactive mono-tetrahydrofuran (THF) annonaceous acetogenins, annomocherin (1), annonacin (2) and annomontacin (3), have been isolated from the fractionated ethanolic extracts of the seeds of Annona cherimolia, guided by the brine shrimp lethality test (BST). Their structures were elucidated on the basis of spectroscopic and chemical methods. All compounds have a relative stereochemistry of threo/trans/threo for the mono-THF ring with two flanking hydroxyls. Compound 1 has a double bond at C-23/ 24 of aliphatic chain. Compound 1 was isolated from natural sources for the first time, and was named annomocherin. Two known Compounds 2 and 3 which have never been isolated from this species before, were obtained. Compound 1 exhibited potent and selective cytotoxicities against the breast carcinoma (MCF-7) and kidney carcinoma (A-498) cell lines with 100 to 1,000 times the potency of adriamycin. In brine shrimp lethality test (BST), 1-3 exhibited cytotoxicity.