• 대한방사성의약품학회지
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• 제4권1호
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• pp.16-21
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• 2018

Organoboron compounds and their derivatives are synthetically versatile building blocks because they are readily available, stable, and highly useful for potential organic transformations. Arylboronic esters are of particular interest due to their well-established synthetic methods: transition metal catalyzed borylations of aryl halides. However, the use of aryl halides as an electrophile has one serious disadvantage: formation of toxic halogenated byproducts. A promising alternative substrate to aryl halides would be phenol derivatives such as aryl ethers, esters, carbamates and sulfonates. The phenol derivatives involve several advantages: their abundance, relatively low toxicity and versatile synthetic application. However, utilization of the aryl methyl ether, which is one of the simplest phenol derivatives, remains as a challenge, as C-OMe bond activation requires high activation energy and methoxides are not good leaving groups. Nevertheless, there have been a significant recent progress on ipso-borylation of aryl methyl ether including Martin's nickel catalysis. Here, we review the current advance on the borylation of carbon-oxygen bonds of unactivated C-OMe bond in aromatic compounds.

• 대한의생명과학회지
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• 제20권2호
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• pp.49-55
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• 2014

RalBP1 is an ATP-dependent non-ABC transporter, responsible for the major transport function in many cells including many cancer cell lines, causing efflux of glutathione-electrophile conjugates of both endogenous metabolites and environmental toxins. RalBP1 is expressed in most human tissues, and is over-expressed in non-small cell lung cancer cell lines and in many other tumor types. Blockade of RalBP1 by various approaches has been shown to increase sensitivity to radiation and chemotherapeutic drugs, leading to cell apoptosis. In xenograft tumor models in mice, RalBP1 blockade or depletion results in complete and sustained regression across many cancer cell types including lung cancer cells. In addition to its transport function, RalBP1 has many other cellular and physiological functions, based on its domain structure which includes a unique Ral-binding domain and a RhoGAP catalytic domain, as well as docking sites for multiple signaling proteins. Additionally, RalBP1 is also important for stromal cell function in tumors, as it was recently shown to be required for efficient endothelial cell function and angiogenesis in solid tumors. In this review, we discuss the cellular and physiological functions of RalBP1 in normal and lung cancer cells.

• Toxicological Research
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• 제23권3호
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• pp.207-214
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• 2007

Chronic oxidative stress produced by exposure to environmental chemicals or pathophysiological states can lead animals to aging, carcinogenesis and degenerative diseases. Indirect antioxidative mechanisms, in which natural or synthetic agents are used to coordinately induce the expression of cellular antioxidant capacity, have been shown to protect cells and organisms from oxidative damages. Electrophile and free radical detoxifying enzymes, which were originally identified as the products of genes induced by cancer chemopreventive agents, are members of this protective system. The NFE2 family transcription factor Nrf2 was found to govern expression of these detoxifying enzymes, and screening for Nrf2-regulated genes has identified many gene categories involved in maintaining cellular redox potential and protection from oxidative damage as Nrf2 downstream genes. Further, studies using Nrf2-deficient mice revealed that these mutant mice showed more susceptible phenotypes towards exposure to environmental chemicals/carcinogens and in oxidative stress related disease models. With the finding that cancer chemopreventive efficacy of indirect antioxidants (enzyme inducers) is lost in the absence of Nrf2, a central role of Nrf2 in the antioxidative protective system has been firmly established. Promising results from cancer prevention clinical trials using enzyme inducers propose that pharmacological interventions that modulate Nrf2 can be an effective strategy to protect tissues from oxidative damage.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1993년도 제2회 신약개발 연구발표회 초록집
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• pp.118-118
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• 1993

퀴놀론 모핵의 합성은 기존에 알려진 합성 방법인 Could-Jacobs방법과 Bayer방법에 의해서 Intermediate로 사용된 7-chloro-1-ethyl-6-fluoro-1, 4-dihydro-4-oxoquinoline-3-carboxylic acid와 1-cyclopropyl-7-chloro-6-Fluoro-1,4-dihydro-4-oxoquinolne-3-carboxylic acid를 합성하였다. Heteroaromatic tin compound는 furan, thiophene, 3-bromopyridine, 2-fluoropyridine에 n-BuLi을 사용하여 metallation 한후 electrophile로 tributyltin chloride를 사용하여 2-tributylstannofuran, 2-tributylst-annothiophene, 3-tributylstannopyridine, 2- fluoro-2-tributylstannop-yridine을 합성할 수 있었다. 이상의 Intermediate와 tin compounds를 p-alladium 촉매하에서 반응시켜 1-ethyl-7-(2-furanyl)-6-fluoro-1,4-dihy-dro-4-oxo-3-quinoline-carboxylic acid (compound 3), 1-ethyl-7-(2-th-iophenyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinol in carboxylic acid(compound 5), 1-ethyl-7-(3-pyridinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid (compound 7), 1-ethyl-7-(2-fluoro-3-pyrid-nyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid (compound 9), 1-cyclopropyl-7-(2-furanyl) -6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid (compound 4), 1-cyclopropyl-7-(2-thiophenyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid (compound 6) ,1-cyclopropyl-7-(3-pyridinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid (compound 8), 1-cyclopropyl-7-(2-fluoro-3-pyridinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid (compound 10)를 합성하였다.

• 대한화학회지
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• 제34권3호
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• pp.248-254
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• 1990

5각-이종원자 방향족 고리화합물들인 푸란, 피롤 그리고 티오펜과 이소프로필 양이온간의 친전자성 친환반응에 관하여 MNDO 방법을 사용하여 이론적으로 연구하였다. ${\alpha},{\beta}$ 그리고 이종원자 방향족 고리화합물의 HOMO간의 전하전이 안정화(Charge transfer stabilization) 효과에 의하여 주로 결정됨을 알 수 있었다. 한편 $\alpha$ 와 $\beta$ 위치에 대한 반응성의 순서는 피롤>푸란>티오펜의 순서를 가지며 이러한 순서는 기체상 및 용액상 실험결과와 잘 일치하는 것이다.

• 통합자연과학논문집
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• 제7권4호
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• pp.266-272
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• 2014

Oxocane high explosives substituted to explosive group such as azide (-CH2N3), nitrate (-CH2ONO2), and hydrazine (-CH2N2H3) are investigated theoretically the acid catalyzed reaction using the semiempirical MINDO/3, MNDO and AM1 methods to use as the guidelines of high explosives. The nucleophilicity and basicity of oxocane high explosives can be explained by the value of negative charge on oxygen atom of oxocane and the reactivity in propagation step can be represented by the value of positive charge on carbon atom and low electrophile LUMO energy. It was known that carbenium ion was favorable due to the stable energy (11.745~25.461 Kcal/mol) between oxonium ion and carbenium ion in the process of cyclic oxonium ion of oxocane high explosives being converted to open carbenium ion in oxocane high explosives. The value of concentration of cyclic oxonium ion and open carbenium ion in equilibrium status was found to be a major determinant of mechanism, it was expected to react faster in the prepolymer propagation step in SN1 mechanism than in that of SN2.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1346-1350
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• 2004

Pseudo-first order rate constants $(k_{obs})$ are reported for the following solvolyses in approximately isodielectric mixtures: 3- and 4-methoxybenzyl chloride, bromo- and chlorodiphenylmethane, and 4-chloro-, 4,4'-dichloro and 4-methyl-chlorodiphenylmethane in 0-80% v/v nitromethane-methanol mixtures; and bromo- and chlorodiphenylmethane and 4-methyl-chlorodiphenylmethane in various acetonitrile-methanol mixtures (in the range 0-50% v/v) at$25^{\circ}C.$ These data, and literature data for t-butyl halides (Cl, Br, and I), and for p-methoxybenzoyl chloride, show rate maxima in solvent compositions of ca. 30% aprotic cosolvent, explained by a stoichiometric solvent effect on electrophilic solvation. Linear relationships are observed between $(k_{obs})/[MeOH]^2$ and [AP]/[MeOH], where [AP] refers to the molar concentration of aprotic cosolvent. The results are consistent with competing third order contributions to $k_{obs}$, $k_{MM}[MeOH]^2$ with hydrogen-bonded methanol as electrophile, and $k_{MAP}[MeOH][AP]$ with hydrogen-bonding disrupted by the aprotic solvent.

• Bulletin of the Korean Chemical Society
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• 제24권9호
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• pp.1293-1302
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• 2003

Rate constants at various temperatures and activation parameters are reported for solvolyses of acyl chlorides (RCOCl), with R = Me, Et, i-Pr, t-Bu, cyclopentylmethyl, benzyl, thiophenylmethyl, 2-phenylethyl, diphenylmethyl, and phenylthiomethyl in 100% ethanol, 100% 2,2,2-trifluoroethanol (TFE), 80% v/v ethanol/ water and 97% w/w TFE/water. Additional rate constants for solvolyses with R = Me, t-Bu, and $PhCH_2$ are reported for TFE/water and TFE/ethanol mixtures, and for solvolyses with R = t-Bu, and PhCH2 are reported for 1,1,1,3,3,3-hexafluoropropan-2-ol/water mixtures, as well as selected kinetic solvent isotope effects (MeOH/MeOD and TFE). Taft plots show that electron withdrawing groups (EWG) decrease reactivity significantly in TFE, but increase reactivity slightly in ethanol. Correlation of solvent effects using the extended Grunwald-Winstein (GW) equation shows an increasing sensitivity to solvent nucleophilicity for EWG. The effect of solvent stoichiometry in assumed third order reactions is evaluated for TFE/ethanol mixtures, which do not fit well in GW plots for R = Me, and t-Bu, and it is proposed that one molecule of TFE may have a specific role as electrophile; in contrast, reactions of substrates containing an EWG can be explained by third order reactions in which one molecule of solvent (ethanol or TFE) acts as a nucleophile, and a molecule of ethanol acts as a general base catalyst. Isokinetic relationships are also investigated.

• 한국환경성돌연변이발암원학회:학술대회논문집
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• 한국환경성돌연변이발암원학회 2002년도 Current Trends in Toxicological Sciences
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• pp.25-35
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• 2002

Transcription factor Nrf2 is essential for the antioxidant responsive element (ARE)-mediated induction of phase II detoxifying and oxidative stress enzyme genes. Detailed analysis of differential Nrf2 activity displayed in transfected cell lines ultimately led to the identification of a new protein, which we named Keap1, that suppresses Nrf2 transcriptional activity by specific binding to its evolutionarily conserved amino-terminal regulatory domain. The closest homolog of Keap1 is a Drosophila actin-binding protein called Kelch, implying that Keap1 might be a Nrf2 cytoplasmic effector. We then showed that electrophilic agents antagonize Keap1 inhibition of Nrf2 activity in vivo, allowing Nrf2 to traverse from the cytoplasm to the nucleus and potentiate the ARE response. We postulate that Keap1 and Nrf2 constitute a crucial cellular sensor for oxidative stress, and together mediate a key step in the signaling pathway that leads to transcriptional activation by this novel Nrf2 nuclear shuttling mechanism. The activation of Nrf2 leads in turn to the induction of phase II enzyme and antioxidative stress genes in response to electrophiles and reactive oxygen species.

• 공업화학
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• 제20권2호
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• pp.159-164
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• 2009

제5류 위험물에 속하며 폭발성기를 가진 azido기$(-CH_2N_3)$, nitrato기$(-CH_2ONO_2)$ 그리고 hydrazino기$(-CH_2N_2H_3)$로 치환된 옥세탄 고폭 화약류의 단량체들을 산 촉매하의 중합반응에 관하여 반응성, 반응메카니즘, 반응과정에 대하여 알아보고자 형식전하, 생성열, 에너지 준위를 반경험적인 MINDO/3, MNDO, AM1 방법 등을 사용하여 이론적으로 고찰하였다. 옥세탄 고폭 화약류의 친핵성 및 염기성은 옥세탄 산소원자의 음전하크기로 설명할 수 있고, 산 촉매하의 중합반응은 성장단계에서 옥세탄의 반응성은 중심 탄소원자의 양전하크기와 친전자체의 낮은 LUMO 에너지에 좌우됨을 알 수 있었다. 옥세탄 고폭 화약류의 전환되는 과정은 oxonium 이온과 carbenium이온의 안정화 에너지(13.90~31.02 Kcal/mole)를 비교하여 보면 carbenium 이온이 더 유리함을 예측 할 수 있었다. 또한, 평형상태에서 oxonium 이온과 carbenium 이온의 농도가 반응 메카니즘을 좌우하며, 산 촉매하의 중합반응 형태와 계산을 기초로 하여 빠른 평형을 예상하여 볼 때 선폴리머(prepolymer) 성장단계에서 $S_N1$ 메카니즘이 $S_N2$ 메카니즘보다 빠르게 반응 할 것으로 예측되었다.