• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2219-2225
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• 2007

The reaction mechanisms for the cyclizations of N-methyl-2-(2-chloropyridin-3-yloxy)acetamide to 1-methylpyrido[ 3,2-b][1,4]oxazin-2-one and 1-methyl-pyrido[2,3-b][1,4]oxazin-2-one were investigated using ab initio Hartree-Fock, second-order Moller-Plesset perturbation, single point coupled cluster with both single and double substitution, and density functional theory methods. The 5-membered spiro intermediate (2) is optimized from the cyclization of the acyclic reactants through the proton-transfer reaction, and this intermediate proceeds continuously to the 6-membered intermediate through either a stepwise or a concerted reaction. In the stepwise reaction, an N-bridge-type intermediate as a stable structure is optimized, whereas, in the concerted reaction, the O-bridge-type intermediate is not optimized.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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• pp.715-720
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• 2004

Amineterminated, ethylenediamine core polyamidoamine starburst dendrimers of generation 2 (G2), generation 4 (G4) and generation 6 (G6) have been successfully surface-modified via an amide coupling reaction with 4-ethyl, 4'-(3-propionic) bipyridinium cation and the electrochemical behavior of the resulting dendrimers were investigated in aqueous potassium chloride electrolyte solutions. The 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide-mediated reaction resulted in 25-39% end-group functionalization. The water-soluble 4-ethyl, 4'-(3-propylamide) bipyridinium dibromide dendrimers (G2-V2+, G4-V2+ and G6-V2+) were characterized by $^1H$ NMR and UV-Vis spectroscopic methods. The cyclic voltammetric and chronoamperometric experiments were performed to determine the diffusion coefficient and the number of electrons transferred in the process of the first reduction of the viologen-functionalized dendrimers. Adsorption of viologen-functionalized dendrimers at electrode surface was evidenced in the voltammograms. Experimentally determined diffusion coefficients were in good agreement with the values expected from the Stokes-Einstein relation, while the number of electrons transferred concurred with the extent of functionalization determined by $^1H$ NMR and UV-Vis spectra.

• 대한수의학회지
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• 제57권2호
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• pp.79-88
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• 2017

The study of canine vector-borne diseases in the Philippines started in the 1970s but only gained interest in the past decade. Characterization of such diseases in the Philippines remains incomplete, thus, it is necessary to obtain additional information on the prevalence and diversity of canine tick-borne diseases in the country. In this study, blood samples were obtained at two veterinary clinics in Metro Manila, Philippines from 114 dogs suspected of having canine tick-borne pathogens. Polymerase chain reaction (PCR) was performed on whole blood DNA extracts followed by sequencing, and the following pathogens were detected: Hepatozoon (H.) canis (5.26%), Babesia (B.) vogeli (5.26%), Ehrlichia (E.) canis (4.39%), and Anaplasma platys (3.51%). Additionally, a set of multiplex PCR primers were developed to detect H. canis, Babesia spp. (B. canis and B. vogeli), and E. canis in canine blood. Multiplex and conventional single-reaction PCR results for the 114 dog blood samples were similar, except for one H. canis sample. Multiplex PCR is, therefore, a useful tool in screening infected dogs in veterinary clinics. This study's results, together with those of previous studies in the country, show that canine vector-borne pathogens are an emerging veterinary concern in the Philippines.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1579-1582
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• 2009

The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = $NO_2,\;CN,\;CF_3$) with Y-substituted pyridines (Y = 3-$OCH_3,\;H,\;3-CH_3,\;4-CH_3$) in methanol-acetonitrile mixtures were measured by conductometry at 25 ${^{\circ}C}$. It was observed that the rate constant increased in the order of X = 4-$NO_2\;>\;4-CN\;>\;4-CF_3$ and the rate constant also increased in the order of Y = 4-$CH_3\;>\;3-CH_3\;>\;H\;>\;3-OCH_3$. When the solvent composition was varied, the rate constant increased in order of MeCN > 50% MeOH > MeOH. The electrophilic catalysis by methanol may be ascribed to the formation of hydrogen bonds between alcoholic hydrogen and nitrogen of pyridines in ground state. Based on the transition parameters, ${\rho}_S,\;{\rho}_N,\;{\beta}_Y,\;{\rho}_{XY}$ and solvent effects, the reaction seems to proceed via $S_N$Ar-Ad.E mechanism. We also estimated the isokinetic solvent mixtures (${\rho}_{XY}$ = 0) based on cross-interaction constants, where the substituent effects of the substrate and nucleophile are compensated.

• Bulletin of the Korean Chemical Society
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• 제31권3호
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• pp.670-677
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• 2010

A comparative study on the Au(I)-catalyzed and IBr-promoted tandem cyclization of 1,5-enyne was reported. This study provides a meaningful mechanistic insight to the concerted nature of this tandem reaction and also provides interesting applications in the synthesis of 7/5- or 8/5-fused bicycles and biaryls.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1545-1553
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• 2008

Using a one-pot reaction technique, monodisperse $\gamma-Fe_2O_3$ nanoparticles were prepared by thermal decomposition of Fe$(CO)_5$ in the presence of a long alkyl chain terminated dendron surfactant. The size of the particles is controlled by adjusting the concentration of the dendron ligands in the reaction solution. Spherical, 2 nm sized nanoparticles were obtained with a 3:1 ratio of dendrons to Fe$(CO)_5$, while 4.6 nm sized particles were formed with a 1:3 ratio. Superparamagetic properties of 2 nm, 4 nm, and 4.6 nm sized particles were measured using a SQUID magnetometer.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.79-84
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• 2004

We evaluated the reduction performance of NOx storage catalyst and TWC for lean-burn natural gas engine by the model gas. The method of unsteady state reaction was used to compare with reduction performances of NOx storage catalyst and TWC. It was found that the effective parameter was rich spike duration, temperature of the model gas. In the presence of $CO_2$ and $H_2O$ in the reaction mixture was decreased the NOx reduction performance.

• Bulletin of the Korean Chemical Society
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• 제27권12호
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• pp.2023-2027
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• 2006

Dibenzyl sulfide was oxidized at the a-carbon to yield benzaldehyde in the presence of $Pd(NO_3)_2$. Oxygen itself could not oxidize the sulfide directly, instead the nitrato ligand of the palladium complex transferred oxygen to dibenzyl sulfide to form benzaldehyde. The X-ray crystal structure of the intermediate complex, cis-[$Pd(NO_3)_2${$S(CH_2C_6H_5)_2$}$_2$], revealed that the nitrato ligand was unidentate. Para-substituted dibenzyl sulfides I, $(YC_6H_4CH_2)_2S $wherein Y = $OCH_3$, $CH_3$, Cl, CN, or $NO_2$, were synthesized and reacted with palladium nitrate, and those with electron-donating substituents (Y = $OCH_3$ and $CH_3$) were good substrates for the oxidation reaction with palladium nitrate. Thus, the reaction mechanism of the oxygen transfer was proposed to include nucleophilic benzylic carbon.

• Bulletin of the Korean Chemical Society
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• 제7권6호
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• pp.453-457
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• 1986

Stereochemical control of the Wittig reaction of the primary aldehyde, 8-acetoxyoctan-1-al (7) with the nonstabilized alkylide, triphenylphosphonium n-butylide (6), was achieved by controlling the reaction conditions including solvent, temperature and inorganic salts. These conditions can be applied to the direct sythesis of the mixture of (Z)-, and (E)-8-dodecen-1-yl acetate, the sex pheromone of the oriental fruit moth, Grapholitha molesta. The primary aldehyde, 8-acetoxyoctan-1-al (7) was synthesized from 1,8-octanediol which is cheap and readily available.

• 약학회지
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• 제38권5호
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• pp.579-585
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• 1994

Antitumor activity was tested by administration of reaction mixture of green onion extract and chitin to mice bearing sarcoma-180 cells. An intraperitoneal injection of mixture(20 mg/kg/day) to mice Have an 52% inhibition of tumor growth. Inhibition of tumor growth was found to be dose-dependent. When eighty miligrams of the mixture were administered, the weight of tumor was reduced significantly. HPLC analysis indicated the mixture was composed of N-acetyl-D-glucosamine, N-acetylchitobiose and N-acetylchitotriose.