• Bulletin of the Korean Chemical Society
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• 제18권2호
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• pp.161-164
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• 1997

Kinetic studies are carried out on the reactions of 1- and 2-naphthylmethyl arenesulfonates with anilines in acetonitrile at 25.0 ℃. The rates are faster for the 2-naphthylmethyl series than for the corresponding 1-naphthylmethyl series suggesting that there is a greater stabilization of positive charge development in the TS at the arylmethyl reaction center carbon for the former. The sign and magnitude of ρxz (=-0.12) are similar to those of the benzylic series. Thus, benzyl, 1- and 2-naphthylmethyl derivatives belong to a class of compounds which react with aniline nucleophiles through a relatively loose SN2 TS. Kinetic secondary deuterium isotope effects indicated that a stronger nucleophile and nucleofuge lead to a later TS as the definition of ρxz requires.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.350.2-350.2
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• 2002

The reaction of N-acyliminium ion with a variety of nucleophiles is one of the powerful method to introduce various substituents at the a-carbon of an amine. Particularly this type of inter and intramolecular C-C bond formation can be effectively applied to the synthesis of the bioactive natural or unnatural compounds as well as many bioactive peptidomimetics. Accordingly. much attention has been devoted to the practical and efficient methods for the generation of acyliminium ion precursors though there are many important aspects in the reaction involving N-acyliminium ions. (omitted)

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.51-56
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• 2008

The regioselective ring opening of epoxides using elemental iodine and bromine in the presence of methimazole (MMI, a anti-thyroid drug) and its metabolite methimazole-disulfide as new catalysts are studied. MMI easily converted in vitro to MMI-disulfide without any double activation presented in vivo. FT-Raman and UV spectroscopies are used to study the interaction of iodine with these catalysts. The results indicate that both catalysts are efficient in polyiodide formation, but MMI-disulfide can catalyze this reaction in higher yield and regioselectivity. The complex [(MMI-disulfide)I]+.I3- is considered to be formed initially which could be bulkier by addition of excess of iodine in the course of the reaction. These bulky nucleophiles have a fundamental role in the high regioselectivity by attacking the less sterically hindered epoxide carbon. In this study we suggest that MMI is readily converted to MMI-disulfide by interaction with iodine or activated iodine in thyroid gland, and this process is responsible for high anti-thyroid activity of MMI.

• 대한화학회지
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• 제34권3호
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• pp.232-238
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• 1990

Zn의 생화학적 역할을 연구하기 위하여, 간단한 모델시스템을 설정하였다. 즉, Zn가 리간드인 $OH_2나 NH_3$와 배위결합을 이루거나 carboxypeptidase A (CPA)의 기질에 해당하는 펩티드의 O=C-와 배위결합을 할 때, 그 기하학적 구조 및 net atomic charge의 변화를 조사하였다. Double Zeta basis set를 사용한 ab initio HF-SCF 계산에 의하면, Zn는 이들 리간드의 O-H, N-H, O=C-를 매우 polar하게 만든다. 특히, 펩티드의 탄소는 친전자성이 매우 증가하여, nucleophile의 공격을 용이하게 받을 수 있을 것으로 예측되었다. 또한, CPA에서 Zn 주위에 있는 리간드의 분자배위 상태를 조사하기 위하여, CPA+glycyltyrosine complex에 관한 molecular mechanics방법을 적용하였다. 이 결과를 X-ray 결과와 비교하였을 때, Zn는 4배위 결합 이외에 물분자도 관여할 것으로 예측된다.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.857-862
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• 2011

Kinetic studies of the reactions of N-methyl-Y-${\alpha}$-bromoacetanilides with substituted X-benzylamines have been carried out in dimethyl sulfoxide at $25.0^{\circ}C$. The Hammett plots for substituent X variations in the nucleophiles (log $k_N$ vs ${\sigma}_X$) are slightly biphasic concave upwards/downwards, while the Bronsted plots (log $k_N$ vs $pK_a$) are biphasic concave downwards with breakpoints at X = H. The Hammett plots for substituent Y variations in the substrates (log $k_N$ vs ${\sigma}_Y$) are biphasic concave upwards/downwards with breakpoints at Y = H. The cross-interaction constant $\rho_{XY}$ values are all negative: $\rho_{XY}$ = -0.32 for X = Y = electron-donating; -0.22 for X = electron-withdrawing and Y = electron-donating; -1.80 for X = electron-donating and Y = electronwithdrawing; -1.43 for X = Y = electron-withdrawing substituents. Deuterated kinetic isotope effects are primary normal ($k_H/k_D$ > 1) for Y = electron-donating, while secondary inverse ($k_H/k_D$ < 1) for Y = electronwithdrawing substituent. The proposed mechanisms of the benzylaminolyses of N-methyl-Y-${\alpha}$-bromoacetanilides are a concerted mechanism with a five membered ring TS involving hydrogen bonding between hydrogen (deuterium) atom in N-H(D) and oxygen atom in C = O for Y = electron-donating, while a concerted mechanism with an enolate-like TS in which the nucleophile attacks the ${\alpha}$-carbon for Y = electronwithdrawing substituents.