• Bulletin of the Korean Chemical Society
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• v.15 no.2
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• pp.154-161
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• 1994

Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethylthioalkyl)phthalimides (alkyl=ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl). Photocyclizations occur in methanol in modest to high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from sulfur in the ${\alpha}$-silylmethylthioalkyl groups to the singlet excited state phthalimide moieties followed by desilylation of the intermediate ${\alpha}$ -silylmethylthio cation radicals and cyclization by radical coupling is proposed. In contrast, photoreactions of N-(trimethylsilylmethylthioalkyl)phthalimides in acetone follow different reaction routes to produce another cyclized products in which carbon-carbon bond formation takes place between the phthalimide carbonyl carbon and the carbon ${\alpha}$ to silicon and sulfur atoms via triplet carbonyl hydrogen abstraction pathway. The normal singlet SET pathway dominates this triplet process for photoreactions of these substances in methanol while the triplet process dominates the singlet SET pathway for those in acetone. The efficient and regioselective cyclization reactions observed for photolyses in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.

• Bulletin of the Korean Chemical Society
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• v.13 no.2
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• pp.166-172
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• 1992

Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethoxyalkyl)phthalimides(alkyl=E thyl, n-propyl, n-butyl, n-pentyl, and n-octyl). Photocyclizations occur in methanol in high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from oxygen in the $\alpha-silylmethoxy$ groups to the singlet excited state phthalimide moieties followed by desilylation of the intermediate $\alpha-silylmethoxy$ cation radicals and cyclization by radical coupling are proposed. In contrast, photoreaction of N-(trimethylsilylmethoxyethyl) phthalimide in acetone follows different reaction routes to produce two cyclized products in which carbon-carbon bond formation takes place between the phthalimide carbonyl carbon and the carbon $\alpha$ to silicon and oxygen atoms via triplet carbonyl hydrogen abstraction triplet carbonyl silyl group abstraction pathways. The normal singlet SET pathway dominates these triplet processes for photoreaction of this substance in methanol. The efficient and regioselective cyclization reactions observed for photolysis in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.

• Toxicological Research
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• v.23 no.3
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• pp.189-196
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• 2007

Cytochrome P450 (P450) enzymes are the major catalysts involved in the biotransformation of various drugs, pollutants, carcinogens, and many endogenous compounds. Most of chemical carcinogens are not active by themselves but they require metabolic activation. P450 isozymes playa pivotal role in the metabolic activation. The activation of arylamines and heterocyclic arylamines (HAAs) involves critical N-hydroxylation, usually by P450. CYP1A2 plays an important role in these reactions. Broad exposure to many of these compounds might cause carcinogenicity in animals and humans. On the other hand, P450s can be also involved in the bioactivation of other chemicals including alcohols, aflatoxin B1, acetaminophen, and trichloroethylene, both in humans and in experimental animals. Understanding the P450 metabolic activation of many chemicals is necessary to develop rational strategies for prevention of their toxicities in human health. An important part is the issues of extrapolation between species in predicting risks and variation of P450 enzyme activities in humans.

• Bulletin of the Korean Chemical Society
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• v.21 no.3
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• pp.300-304
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• 2000

The B3LYP method based on the density functional theory(DFT) is shown to be much better than the ab initio MP2 method for structural determination of diphosphadithiatetrazocine systems having transannular S--S bonding. The presence of bonding between the two sulfur atoms across the cyclic ring is theoretically confirmed in the case of the neutral diphosphadithiatetrazocine. The S--S dobding disappears in the ionized species. The planarity of the dicationic heterocyclic ring system turns out to be closely associated with the $\pi-electron$ delocalization over the entire ring as well as the N-S-N bonds, which become stiffened upon ionizaiton. In the case of dianionic species, the chair-boat and chair conformers are nearly degenerate and far more stable than the crown conformer.

• Bulletin of the Korean Chemical Society
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• v.18 no.3
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• pp.311-316
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• 1997

The synthesis and characterization of the mononuclear group 13 heterocyclic carboxaldehyde methyldithiocarbazate complexes Me2M[NC5H4CRNNC(S)SCH3] (M=Al, R=H(1); M=Ga, R=H(2); M=Al, R=CH3(3); M-Ga, R=CH3(4); M=In, R=CH3(5)) are described. Compounds 1-5 were prepared by the reaction of MMe3 (M=Al, Ga, In) with 2-formy or 2-acetylpyridine-S-methyldithiocarbazate in toluene. These compounds 1-5 have been characterized by microanalysis, NMR (1H, 13C) spectroscopy, mass spectra, and single-crystal X-ray diffraction. X-ray single-crystal diffraction analyses reveal that 4-5 are mononuclear metal compounds with coordination number of 5 and N,N,S coordination mode.

• Journal of the Korean Chemical Society
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• v.38 no.12
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• pp.908-914
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• 1994

6a-Hydroxy- and 6a-methoxy-derivatives (1∼6) of octahydro-2,3-dioxo-cyclopenta[b]-pyrrole-3a-carboxylate were synthesized from oxalylation of enamine A, which was prepared from condensation of five-membered cyclic ${\beta}$-keto ester and phenylalkylamine, followed by addition of water or methanol. The formation of heterocyclic ring was assumed to occur by the way of unstable N-acyliminium (B). Stable adduct C (1∼6) was obtained from nucleophilic addition to the endo-ene type pyrrolinium B.

• YAKHAK HOEJI
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• v.38 no.5
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• pp.511-515
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• 1994

We examined the inhibitory activity of (1,3-dioxolan-2-yl and 1,3-dioxan-2-yl)methylaminium derivatives(A; 1-8) against acetylcholinesterase. Derivatives of six-membered 1,3-dioxane exhibited more potent inhibitory effect than corresponding 5-membered 1,3-dioxolanes. The presence of methyl group at C4 position of dioxane ring was effective to increase the inhibitory potency of heterocyclic analogues. The activity of N-phenacyl-aminiums was greater than that of N,N,N-trimethyl-aminiums. In general, the terminal methyl group on 1,3-dioxane ring and the phenacyl group in ammonium compound A were assumed to be important factors to enhance the inhibitory action.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1457-1464
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• 2012

An ecofriendly catalytic route for selective synthesis of $N$-substituted azacyclopentanes, nitrogen-containing heterocyclic intermediates for many bioactive compounds, was established by carrying out $N$-heterocyclization (di $N$-alkylation) of primary amines with 1,4-dichloro butane (as dialkylating agent) using catalytic amount of hydrotalcite as solid base catalyst. The hydrotalcite was found to be efficient solid base catalyst for di $N$-alkylation of different primary amines (aniline, benzyl amine, cyclohexyl amine and n-butyl amine) giving 82 to 96% conversion (at optimized reaction condition) of 1,4-dichloro butane and > 99% selectivity of respective $N$-substituted azacyclopentanes within 30 min. under solvent free condition. The reaction parameters significantly influence the conversion of 1,4-dichloro butane to $N$-substituted azacyclopentanes. The nature of substituent present on amino group affects the reactivity of amine substrates for di $N$-alkylation reaction with 1,4-dichloro butane. The 1,4-dichloro butane was found to be highly reactive alkylating agent for di $N$-alkylation of amines as compared to 1,4-dihydroxy butane. The reusability of the catalyst and its chemical stability in the reaction was demonstrated.

• Toxicological Research
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• v.31 no.3
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• pp.255-264
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• 2015

Heterocyclic amines (HCAs) and acrylamide are unintended hazardous substances generated by heating or processing of foods and are known as carcinogenic and mutagenic agents by the animal experiments. A simple method was established for a rapid and accurate determination of 12 types of HCAs (IQ, MeIQ, Glu-P-1, Glu-P-2, MeIQx, Trp-P-1, Trp-P-2, PhIP, $A{\alpha}C$, $MeA{\alpha}C$, Harman and Norharman) and acrylamide in three food matrices (non-fat liquid, non-fat solid and fat solid) by isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS). In every sample, a mixture of internal standards including $IQ-d_3$, $MeIQx-d_3$, $PhIP-d_3$, $Trp-P-2-^{13}C_2-^{15}N$ and $MeA{\alpha}C-d_3$ was spiked for quantification of HCAs and $^{13}C_3$-acrylamide was also spiked for the analysis of acrylamide. HCAs and acrylamide in sample were extracted with acetonitrile and water, respectively, and then two solid-phase extraction cartridges, ChemElut: HLB for HCAs and Accucat: HLB for acrylamide, were used for efficiently removing interferences such as pigment, lipid, polar, nonpolar and ionic compounds. Established method was validated in terms of recovery, accuracy, precision, limit of detection, limit of quantitation, and linearity. This method showed good precision (RSD < 20%), accuracy (71.8~119.1%) and recovery (66.0~118.9%). The detection limits were < 3.1 ng/g for all analytes. The correlation coefficients for all the HCAs and acrylamide were > 0.995, showing excellent linearity. These methods for the detection of HCAs and acrylamide by LC-MS/MS were applied to real samples and were successfully used for quantitative monitoring in the total diet study and this can be applied to risk assessment in various food matrices.

• Analytical Science and Technology
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• v.18 no.5
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• pp.386-390
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• 2005

The zinc(II) complex, $Zn(NCS)_2(C_3H_4N_2S)_2$, I, has been synthesized and characterized by single crystal X-ray diffraction, thermal analysis and infrared spectroscopy. The complex I crystallizes in the triclinic system, $P\bar{1}$ space group with a = 7.587(1), b = 8.815(1), $c=12.432(2){\AA}$, ${\alpha}=75.584(8)$, ${\beta}=83.533(9)$, ${\gamma}=68.686(8)^{\circ}$, $V=750.0(2){\AA}^3$, Z = 2, $R_1=0.036$ and ${\omega}R_2=0.101$. The central Zn(II) atom has a tetrahedral coordination geometry, with the heterocyclic nitrogen atoms of 2-aminothiazole ligands and the nitrogen atoms of isothiocyanate ligands. The crystal structure is stabilized by one-dimensional networks of the intermolecular $N-H{\cdots}S$ hydrogen bonds between the amino group of 2-aminothiazole ligands and the sulfur atom of isothiocyanate ligands. Based on the results of thermal analysis, the thermal decomposition reaction of complex I was analyzed to have three distinctive stages such as the loss of 2-aminothiazole, the decomposition of isothiocyanate and the formation of metal oxide.