• Proceedings of the PSK Conference
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• 2003.10b
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• pp.172.2-173
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• 2003

3-Alkoxy-6-allylthiopyridazine derivatives showed the strongest protective effect against oxidative stress and their anticancer effect determined on the growth of SK-Hep-l hepatocellular carcinomar cells. The allythio group as a pharmacologically active group was introduced into pyridazine nucleus and a substituent such as halogen or alkoxy was also introduced into paraposition of allylthio group. Five kinds of 3-alkoxy-6-allylthiopyridazine derivatives were synthesized and their chemoprotective activities examined in rats exposed to aflatoxin $B_1$-toxicant. (omitted)

• Journal of the Korean Chemical Society
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• v.26 no.5
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• pp.333-339
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• 1982

Substituent effects of substrate and leaving group for the reaction of substituted ${\beta}$-phenylethyl arenesulfonates with pyridine were determined conductometrically in acetonitrile at 50∼70$^{\circ}$C. The substituent effect in substrate is not so significant than expected, but still the electron donating substituent shows the slight acceleration to give a small negative ${\rho}$ value and Hammett plots show slight curvature on the acting substituents, even though it is not so remarkable than that of benzyl system. These results represent a little bit the favorable bond breaking at the transition state by the electron donating substituents. The effects of leaving group in the arenesulfonates in which the rate constants are decreased by electron donating substituents, while electron withdrawing groups presented the reverse effects. Hammett ${\rho}$ value is significantly smaller than that of p-nitrobenzyl arenesulfonates and thus, the mechanism should be closer to tight $S_N2$ one. Especially 2,5-dichlorobenzenesulfonate was more accelerated than expected at the additivity of substituents. This facts showed that dichlorobenzenesulfonate anion is more stabilized by the great electron withdrawing substituents at transition state.

• Applied Biological Chemistry
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• v.42 no.1
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• pp.68-72
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• 1999

The cytotoxicity of 1,3-diphenylpropenone derivatives known to inhibit the farnesyl protein transferase (FPTase) was examined against various established tumor cell line, A549 (lung cancer), SKMEL-2 (uterine cancer), HCT-15 (skin cancer), SKOV-3 (brain cancer) and XF-498 (colon cancer) of the 1,3-diphenylpropenone derivatives showing farnesyl protein transferase (FPTase) inhibition activity. And the structure-activity relationship (SAR) between structure of 1,3-diphenylpropenone derivatives as substrate and cytotoxicity was investigated by Free-Wilson analysis as well as Hansch method with tumor cell lines. From the result of Free-Wilson analyses, X-substituents on the benzoyl group have a more important role than Y-substituents on the styryl group. The 2,4-dichloro substituent, 15 and 2,4-dimethyl substituent, 16 showed the highest cytotoxicity (average pI_(50)=5.0). Particulary, the cytotoxicity of X-substituents increased with electronic effect $({\sigma})$ due to weak electron withdrawing group with optimum value $({\sigma}_{opt}=0.22{\sim}0.29})$ whereas that of Y-substituent resulted from various factors such as logP, $B_1$ and R constant.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.280-286
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• 2015

Two series of unsymmetric dimesogenic compounds containing a butylene or pentamethylene group as the flexible spacer were synthesized and their thermal and mesomorphic properties were studied. Mesogenic groups of the synthesized compounds consisted of a cholesteryl and an azobenzene group with lateral substituent. Chemical structures and mesomorphic properties of the synthesized compounds were investigated by FT-IR, $^1H$-NMR, differential scanning calorimeter (DSC), and polarizing optical microscope (POM). All synthesized compounds, apart from $D5-OCH_3$, showed enantiotropic liquid crystal phases. Compounds having an even number of carbon atoms in the flexible spacer exhibited wide mesophase temperature ranges and high isotropic transition temperatures. Regarding the effect of lateral substituents, compounds with bulky substituents exhibited decreased mesophase temperature ranges and isotropic transition temperatures, while those with polar substituents showed the increased thermal stability of the smectic phase.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2135-2138
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• 2014

A kinetic study is reported for the SNAr reaction of 1-Y-substituted-phenoxy-2,4-dinitrobenzenes (1a-1h) with OH- in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The second-order rate constant ($k_{OH^-}$) increases as the substituent Y in the leaving group changes from an electron-donating group (EDG) to an electronwithdrawing group (EWG). The Br${\o}$nsted-type plot for the reactions of 1a-1h is linear with ${\beta}_{lg}$ = -0.16, indicating that the reactivity of substrates 1a-1h is little affected by the leaving-group basicity. A linear Br${\o}$nsted-type plot with ${\beta}_{lg}=-0.3{\pm}0.1$ is typical for reactions reported previously to proceed through a stepwise mechanism in which formation of a Meisenheimer complex is the rate-determining step (RDS). The Hammett plot correlated with ${\sigma}_Y{^{\circ}}$ constants results in a much better correlation than that correlated with ${\sigma}_Y{^-}$constants, implyng that no negative charge is developing on the O atom of the leaving group (or expulsion of the leaving group is not advanced at all in the TS). This excludes a possibility that the $S_NAr$ reaction of 1a-1h with $OH^-$ proceeds through a concerted mechanism or via a stepwise pathway with expulsion of the leaving group being the RDS. Thus, the current reactions have been concluded to proceed through a stepwise mechanism in which expulsion of the leaving group occurs rapidly after the RDS.

• Journal of the Korean Chemical Society
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• v.26 no.1
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• pp.7-17
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• 1982

In order to predict substituent and Lewis acid effects on the regiospecificity of the Diels-Alder reaction, and to investigate the competition for the complexation of Lewis acid between diene and dienophile, frontier orbital theory has been applied to thermal and catalyzed Diels-Alder reaction by means of CNDO/2 MO method. It has been found that: (1) Lewis acid coordinated preferentially with diene rather than dienophile when carbonyl oxygen of acetoxy substituted diene had larger negative atomic charges than that of dienophile. (2) Most of the reaction were neutral electron demand type, and hence 4-C, 2-C and quantitative secondary orbital interacion methods were generally in good accord with experiments. (3) Sulfur activated the adjacent terminal carbon atom greatly to increase diene LUMO-dienophile HOMO interaction through vacant-d-orbital participation, and played an important role in controlling regioselectivity of neutral electron demand reaction type.

• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1525-1530
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• 2004

Mutagen X (MX) exists in our drinking water as the bi-products of chlorine disinfection. Being one of the most potent mutagen, it attracted much attention from many researchers. MX and its analogs are synthesized and modeled by quantitative structure activity relationship (QSAR) methods. As a result, factors affecting this class of compounds have been found to be steric and electrostatic effects. We tried to collect all the data available from the literature. With both CoMFA and CoMSIA various combinations of physiochemical parameters were systematically studied to produce reasonable 3-dimensional models. The best model for CoMFA gave $q^2$ = 0.90 and $r^2$ = 0.97, while for CoMSIA $q^2$ = 0.85 and $r^2$ = 0.94. So the models seem to be reasonable. Unlike previous result of CoMFA, in our case steric parameter alone gave the best statistics. Although the steric contribution was found to be the most important in both CoMFA and CoMSIA, steric parameter along with electrostatic parameter produced slightly better model in CoMSIA. Overall, steric contribution is clearly the most important single factor. However, when we compare chlorine and bromine substitution, chlorine substitution can be more mutagenic. This indicates that other factors such as electrostatic effect also influence the mutagenicity. From the contour maps, steric contribution seems to be focused on rather small area near C6 substituent of the furanone ring, rather than C3 substituent. Therefore the locality of steric contribution can play a significant role in mutagenicity.

• Journal of the Korean Chemical Society
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• v.39 no.11
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• pp.842-847
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• 1995

The electrochemical reduction reactions of N '-aryl-N-alkyl-N-nitrosourea derivatives with a glassy carbon electrode were diffusion controlled and irreversible. The exchange kinetic constant ko values for reduction reaction of the N '-aryl-N-alkyl-N-nitrosoureas were at the range of $1.48{\times}10^{-6}{\sim}5.32{\times}10^{-7}\;cm/sec.$ The $k_0$ values for phenyl substituted on the aryl position were about 1.3∼2.8 times higher than that of other substituents. The same substituent for aryl groups on the both of N '-aryl-N-alkyl-N-nitrosourea and N '-aryl-N-(2-chloroethyl)-N-nitrosourea exhibited same value. The $E_p$ value was shifted to the negative direction as pH increased. The number of protons participated to the reduction was 4∼5, respectively. The substituent effect of aryl group on the reduction potential was not observed in this case.

• Journal of the Korean Applied Science and Technology
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• v.8 no.2
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• pp.161-167
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• 1991

The kinetics of hydrolysis of cinnamenylisophorone derivatives (${rho}-H,\;{rho}-Br,\;P-Cl,\;{rho}-OCH_3$) was investigated using ultraviolet spectrophotometry in 20%(v/v) dicxane-$H_2O$ at 25$^{\circ}C$. A rate equation which can be applied over wide pH range (pH $1.0{\sim}13.0$) was obtained. In order to investigate the substituent effects on cinnarnenylisophorone derivatives, Hammett constant was plotted. As the result, the rate of hydrolysis of cinnamenylisophorone derivatives was facilitated by electron donating group. Final products of the hydrolysis were benzaldehyde and isophorone, From the measurement of reaction rate constant according to pH changes, substituent effect, and final products, it was found that the hydrolysis of cinnarnenylisophorone derivatives was initiated by the neutral $H_2O$ molecule which does not dissociated at below pH 9.0, and in the range of pH $9.0{\sim}11.0$ this reaction occurs by $H_2O$ or hydroxide ion competitively, but proceeded by the hydroxide ion above pH 11.0. On the basis of this kinetic study, the reaction mechanism of the hydrolysis of cinnamenylisophorone derivatives was proposed.

• Applied Biological Chemistry
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• v.33 no.3
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• pp.231-238
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• 1990

The structure-antifungal activity correlations between the structure of fourteen new 1-(phenoxymethyl)benzotriazoles (I) (Y=0), 1-(thiophenoxymethyl)benzotriazoles (ll) (Y=S) and 1-(azidomethyl)benzotriazole (III) derivatives were synthesized, and their activity, fifty percent inhibition of mycelial growth($pI_{50}$), in vitro against Pyricularia oryzae, Fusarium axysporum f.sp sesami, Valsa ceratosperma and Botrytis cinerea were investigated using a generalized QSAR method. The activity of (I) was superior In those of (II) and (III). The effect of the substituents (X) on the phenoxy group (I) was rationalized by a parabolic function of electronic (${\sigma}$), steric ($B_1$) and hydrophobic parameter(${\pi}$), and hydrogen bonding (HB). Where the optimal values of substituent on the fungicidal activity againt P. oryzae and F. axysporum f.sp.sesami are $B_1=1.40A;(H)$ and ${\pi}=0.07{\sim}0.15;(H)$, and those of substituent on the fungicidal activity against V. ceratosperma and B. cinerea are ${\sigma}=0.23{\sim}0.28;\;(C1),\;{\pi}=0.70;$ (C1), respectively. The most effective compound ( I a) and ( I d) were examined in this study.