• 대한화학회지
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• 제29권6호
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• pp.651-655
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• 1985

물-메탄올(9:1) 용매 속에서 ${\beta},\;{\beta}$-diethoxycarbonylstyrene과 L-glutathione을 반응시켜 좋은 수득율로 다음과 같은 화합물을 합성하였다. 즉 S-(2,2-diethoxycarbonyl-1-phenylethyl)-L-glutathione, S-2,2-diethoxycarbonyl-1-(3',4'-methylenedioxy)phenylethyl-L-glutathione, S-2,2-diethoxycarbonyl-1-(3',4',5'-trimethoxy)phenylethyl-L-glutathione, S-2,2-diethoxycarbonyl-1-(4'-hydroxy)phenylethyl-L-glutathione, S-2,2-diethoxycarbonyl-1-(4'-methoxy)phenylethyl-L-glutathione. 위 화합물들의 구조는 원소분석과 분광학적 방법으로 확인하였고 수득율에 미치는 pH와 용매의 영향을 실험한 결과 pH는 4.0에서 8.0사이가 용매는 물-메탄올이 가장 적합하다는 것을 알았다. 한편 이 화합물의 Gram(+) 박테리아에 대한 항균성을 실험한 결과 약함을 알았다.

• 대한화학회지
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• 제33권1호
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• pp.97-105
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• 1989

CTABr 미셀용액 속에서의 2-alkylbenzimidazole(R-BI) 및 sodium 2-alkylbenzimidazole-5-sulfonate(R-BISO$_3$Na)에 의해 추진되는 p-nitrophenyl carboxylic esters(p-NPCE)들의 가수분해반응에 대한 미셀효과를 다루었다. 이들 반응은 각각 BI 및 BISO$_3$Na에 의해 추진되는 반응의 속도보다 현저히 감소하고, 알킬기가 methyl에서 heptyl로 길어질수록 감소의 정도가 더욱 크다. 이것은 CTABr을 포함하지 않는 수용액속에서의 BISO$_3$Na와 R-BISO$_3$Na에 의한 가수분해 반응속도가 별차이가 없음을 감안 할 때, 미셀의사층(micellar pseudophase) 내에서 이들 친핵체의 알킬기가 입체장해(steric hindrance)로 작용하기 때문이다. 이것은 수용액과 미셀용액 속에서의 반응의 측정된 홀성화에너지(${\Delta}H{\neq},\;{\Delta}G{\neq}$ 및 ${\Delta}S{\neq}$)의 값과도 정성적으로 일치하고 있다. 한편, nonyl기에서 pentadecyl기까지의 긴 알킬기를 갖고 있는 R-BISO$_3$Na는 그것의 imidazole 부분(BI moiety)이 친핵체로 작용할 뿐 아니라, 이들은 CTABr을 포함하지 않는 수용액속에서 미셀을 형성하고, 그 결과 기질인 p-NPCE를 쉽게 수용하여 반응속도를 촉진시키는 것으로 판단된다. R-BISO$_3$Na에 의한 이들 p-NPCE들의 가수분해반응의 mechanism을 알기위하여 중수소 동위원소효과(kinetic isotope effect)를 측정하였다. $k'_{H_2O}/K'_{D_2O}$값이 약 2.5∼3.2의 범위로서, 이 값은 R-BISO$_3$Na가 친핵체로만 작용한다고 보기에는 너무 높고, 일반염기로 작용한다고 보기에는 너무 낮다. 따라서 CTABr 미셀용액 속에서의 이 반응은 이 두 mechanism에 의해 동시적으로 진행된다고 생각된다.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.519-523
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• 2012

A kinetic study is reported on nucleophilic displacement reactions of benzyl 2-pyridyl carbonate 6 with alkalimetal ethoxides, EtOM (M = Li, Na, and K), in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of pseudo-firstorder rate constant $k_{obsd}$ vs. [EtOM] curve upward, a typical phenomenon reported previously for alkaline ethanolysis of esters in which alkali-metal ions behave as a Lewis-acid catalyst. The kobsd value for the reaction of 6 with a fixed EtOK concentration decreases rapidly upon addition of 18-crown-6-ether (18C6), a complexing agent for $K^+$ ion up to [18C6]/[EtOK] = 1.0 and then remains constant thereafter, indicating that the catalytic effect exerted by K+ ion disappears in the presence of excess 18C6. The reactivity of EtOM towards 6 increases in the order $EtO^-$ < EtOLi < EtONa < EtOK, which is contrasting to the reactivity order reported for the corresponding reactions of 2-pyridyl benzoate 4, i.e., $EtO^-$ < EtOK < EtONa < EtOLi. Besides, 6 is 1.7 and 3.5 times more reactive than 4 towards dissociated $EtO^-$ and ion-paired EtOK, respectively. The reactivity difference and the contrasting metal-ion selectivity are discussed in terms of electronic effects and transition-state structures.

• Bulletin of the Korean Chemical Society
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• 제23권1호
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• pp.123-131
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• 2002

Solvolyses rate constant of 1- and 2- naphthoyl chlorides (1 and 2) are reported for aqueous binary mixtures with methanol, ethanol, fluorinated alcohol, acetonitrile and dioxane. Kinetic solvent isotope effects (KISE) in methanol and product selectivities (S) of 2-naphthoyl chloride (2) in alcohol-water are also reported. Dispersions in Grunwald-Winstein correlations $(r{\leq}0.901)$ are discussed by multiple regression analysis incorporating ionizing power $(Y_{Cl})$ scale and rate-rate profiles. Major causes for these phenomena are investigated as an aromatic ring solvation effects, in conjunction with weakly nucleophilic solvation effects ($S_N2$ character), for solvolyses of 1 and for solvolyses of 2, as dual reaction channels, described as $S_N1$-$S_N2$ and $S_AN$-$S_N2$ processes. Distinct border lines between the two pathways are derived from solvolyses rates of 2 in 18 solvent using the results of $log(k/k_o)=mY_{Cl}+lN_T+hI$ plot with values of 1.13 for m, 0.37 for l and 0.15 for h value in 5 aqueous fluorinated alcohol mixtures. Using rate-product correlation, the validity of a third order model based on a general base catalyzed by solvent and contribution from these rate constants, $k_{aa},\;k_{aw}$ and $k_{aw}$, are investigated for $S_AN$-$S_N2$ solvolyses of 2 favored in more rich alcohol media and gradual addition of water to alcohol solvent shows a great shift away from stoichiometric solvation to predominantly medium effects. Rate-rate correlation between solvolyses of 2 and trimethyl acetylchloride (5) with alkyl group in the 29 aqueous solvent mixtures shows appreciable linearity (slope = 0.84, r = 0.987), caused by the same pathway ($S_N1$-$S_N2$ process), even if this correlation coincides with appreciable dispersion (different solvation effect).

• Bulletin of the Korean Chemical Society
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• 제26권12호
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• pp.1981-1985
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• 2005

Kinetic studies have been performed for alkaline hydrolysis of a series of [(methoxy)(p-substituted styryl)carbene]pentacarbonyl chromium(0) complexes ($(CO)_5$Cr=$C(OCH_3)CH=CHC_6H_4X$, X = p-$OCH_3$, p-$CH_3$, H, p-Cl, p-$NO_2$). Second-order rate constants $(k_{{OH}^-})$ for the alkaline hydrolysis in 50% acetonitrile-water(v/v) were determined spectrophotometrically at various temperatures. At a low pH region (pH < 7.5), the observed rate constant $(k_{obs})$ remained constant with a small value, while in a high pH region (pH > 9.5), $k_{obs}$ increases linearly with increasing the pH of the medium. The second-order rate constants $(k_{{OH}^-})$ increase as the substituent X changes from a strong electron donating group to a strong electron withdrawing group. The Hammett plot obtained for the alkaline hydrolysis is consisted of two intersecting straight lines. The nonlinear Hammett plot might be interpreted as a change in the rate-determining step. However, the fact that the corresponding Yukawa-Tsuno plot is linear with $\rho$ and r values of 0.71 and 1.14, respectively indicates that the nonlinear Hammett plot is not due to a change in the rate-determing step but is due to ground-state stabilization through resonance interaction. The positive $\rho$ value suggests that nucleophilic attack by $OH^-$ to form a tetrahedral addition intermediate is the rate-determining step. The large negative ${\Delta}S^\neq$ value determined in the present system is consistent with the proposed mechanism.

• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.1891-1896
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• 2011

On the basis of potent HDAC-inhibitory activity and anticancer activity of SAHA, novel SAHA derivatives 3a-d and 7 with a bulky cap such as p-dimethylaminophenyl, 4-phenylaminophenyl, 4-phenyloxyphenyl, 9H-fluorenyl or naphthalenyl ring were synthesized starting from the corresponding aryl amines or naphthalenyl acetic acid using an EDC-mediated amide coupling reaction in the presence of HOBt followed by a nucleophilic addition-elimination reaction with hydroxylamine. Compounds 3b, 3c and 3d showed more potent inhibitory activity on total HDACs (14~27-fold), HDAC1 (8~15-fold), HDAC2 (1.3~25-fold) and HDAC7 (1~3-fold) and more potent anticancer activity (2~22-fold) against MCF-7, MDA-MB-231, MCF-7/Dox, MCF-7/Tam, SK-OV-3, LNCaP and PC3 human cancer cell lines than SAHA.

• Journal of Microbiology and Biotechnology
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• 제17권11호
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• pp.1789-1796
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• 2007

A ${\beta}$-glucosidase with the molecular mass of 160,000 Da was purified to homogeneity from cell extract of a cellulolytic bacterium, Cellulomonas uda CS1-1. The kinetic parameters ($K_m$ and $V_{max}$) of the enzyme were determined with pNP-cellooligosccharides (DP 1-5) and cellobiose. The molecular orbital theoretical studies on the cellulolytic reactivity between the pNP-cellooligosaccharides as substrate (S) molecules and the purified ${\beta}$-glucosidase (E) were conducted by applying the frontier molecular orbital (FMO) interaction theory. The results of the FMO interaction between E and S molecules verified that the first stage of the reaction was induced by exocyclic cleavage, which occurred in an electrophilic reaction based on a strong charge-controlled reaction between the highest occupied molecular orbital (HOMO) energy of the S molecule and the lowest occupied molecular orbital (LUMO) energy of the hydronium ion ($H_3O^+$), more than endocyclic cleavage, whereas a nucleophilic substitution reaction was induced by an orbital-controlled reaction between the LUMO energy of the oxonium ion ($SH^+$) protonated to the S molecule and the HOMO energy of the $H_2O_2$ molecule. A hypothetic reaction route was proposed with the experimental results in which the enzymatic acid-catalyst hydrolysis reaction of E and S molecules would be progressed via $SN_1$ and $SN_2$ reactions. In addition, the quantitative structure-activity relationships (QSARs) between these kinetic parameters showed that $K_m$ has a significant correlation with hydrophobicity (logP), and specific activity has with dipole moment, respectively.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.

• 대한화학회지
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• 제28권4호
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• pp.259-264
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• 1984

1 : 4 dioxane-물의 혼합용매중에서 benzenesulfonylimido phosgene의 가수분해 반응속도 상수를 자외선 분광법으로 측정하여 넓은 pH범위에서 잘 맞는 반응속도식을 구하였다. Grunwald-Winstein식에 적용하여 pH4.0에서 m=0.4의 값을 얻었으며 열역학적 활성화 파라미터 값은 pH4.0에서 ${\Delta}H^{\neq}$ = 15kcal/mol과 $ {\Delta}S^{\neq}$ =-21e.u 그리고 pH10.0에서는 $ {\Delta}H^{\neq}$ = 8kcal/mol, ${\Delta}S^{\neq}$ = -39e.u.이었다. 이와 같은 결과로부터 잘 알려져 있지않은 benzenesulfonylimido phosgene의 친핵성 첨가-제거 반응메카니즘을 정량적으로 잘 설명할 수 있었다.

• 대한화학회지
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• 제36권4호
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• pp.589-597
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• 1992

$25^{\circ}C$의 30%(v/v) dioxane-물의 혼합용매 속에서 pH 변화에 따른 X와 Y-치환된 phenyl-N-benzo-ylchlorothioformimidates(S)들의 가수분해 반응 속도상수를 측정하여 반응 속도식을 유도하고, 경계 궤도함수 상호작용, 용매 효과, 일반 염기 촉매효과, 열 역학적 활성화 파라미터, 및 가수분해반응 생성물 분석 등의 결과로부터 pH 10.0 이하의 낮은 pH 에서는 azocarbocation 중간체를 지나는 $S_N1$형 반응, pH 11.0이상의 높은 pH에서는 사면체 중간체를 지나는 친핵성 첨가-제거 ($Ad_{N-E}$)반응 그리고 pH 10.0과 11.0 사이에서는 이들 두가지 유형의 궤도 조절 반응이 서로 경쟁적으로 일어남을 제안하였다.