• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2989-2992
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• 2009

An efficient synthetic route of novel 2′(${\alpha}$)-C-fluoro-2′(${\beta}$)-C-methyl carbocyclic nucleoside analogues is described. The key fluorinated intermediate 7 was prepared from the epoxide intermediate 5 via selective ring-opening of epoxide. Coupling of 7 with nucleosidic bases under the Mitsunobu reactions followed by deprotection afforded the target carbocyclic nucleoside analogues. The synthesized compounds were evaluated as inhibitors of the hepatitis C virus (HCV) in Huh-7 cell line in vitro.

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.257-262
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• 2007

The efficient synthesis of a tetrasaccharide, the suitably protected form of the repeat unit, →2)-α-D-Manp-(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp-(1→, of the O-antigen polysaccharide of the lipopolysaccharide from E. coli O77 has been accomplished. Glycosylation reactions for the coupling of four monosaccharide building blocks of the tetrasaccharide were carried out employing the CB glycoside method, the mannosyl 4-pentenoate/PhSeOTf method, and the glycosyl trichloroacetimidate method with complete stereoselectivities in excellent yields.

• Journal of the Korean Chemical Society
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• v.62 no.3
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• pp.187-190
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• 2018

A three-component coupling reaction of phenylacetylene, p-toluenesulfonyl azide, and water through copper catalysis is described to provide knowledge of spectroscopy and catalytic reactions and to introduce current research topics in organic chemistry for second-year undergraduate students. In the presence of stoichiometric amounts of phenylacetylene, p-toluenesulfonyl azide, and triethylamine, the reaction was performed with 4 mol% CuCl in water as the sole solvent and was completed in 1.5 h. A practical purification method and recrystallization of the crude reaction mixture resulted in the rapid isolation of the desired product with yields of 42~65%. Students characterized 4-methyl-N-(phenylacetyl)benzenesulfonamide by using melting-point determination, infrared spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. This experimental procedure and spectroscopic data analysis will serve as a platform for students to apply classroom knowledge in practical state-of-the-art research.

• Journal of Microbiology and Biotechnology
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• v.8 no.3
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• pp.251-257
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• 1998

Cycloinulooligosaccharide fructanotransferase (CFTase) which produces cyclofructan from inulin was purified 332-fold from a culture broth of Bacillus macerans CFCl. The molecular mass of the CFTase was estimated to be 110 kDa by SDS-polyacrylamide gel electrophoresis and gel filtration, indicating that the enzyme has a monomer structure. The maximal level of enzyme activity was observed at pH 7.5 and $45^{\circ}C$. The enzyme was stable in the pH range 6.0 to 9.5, and at temperatures up to $45^{\circ}C$ for 1 h. The enzyme activity was completely inhibited in the presence of 0.5 mM $Ag^+\;or\;Cu^2+$ ion. None of sucrose (GF), l-kestose (GF2), or nystose (GF3) were found to be substrates for the CFTase, but inulooligosaccharides larger than nystose were attacked by the enzyme. The CFTase catalyzes not only the cyclization as the major reaction, but also disproportionation and coupling reactions involving intermolecular transfructosylation in the same manner as cyclodextrin glucanotransferase (CGTase) (EC 2.4.1.19).

• Journal of the Korean Magnetic Resonance Society
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• v.8 no.1
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• pp.62-69
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• 2004

Bicyclolactones obtained from the Diels-Alder cycloaddition of 3,5-dibromo-2-pyrone can undergo various palladium catalyzed cross coupling reactions to afford aryl bicyclolactones. The resulting coupled products can be readily converted into various 3-OH cyclohexenes via lactone ring openings, while those bearing dienyl units underwent highly diastereoselective Diels-Alder cycloadditions with selected dienophiles to funish multiply functionalized polycarbocycles. Bromo-bicyclic diene furnished two different diastereomers endo-form (62%) and exo-form (38%) upon cycloadditions with N-Et maleimide (NEM), and their stereochemistries were identified with NMR.

• Korean Journal of Pharmacognosy
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• v.11 no.1
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• pp.15-23
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• 1980

A new iridoid glucoside was isolated from the whole plant of Ajuga spectabilis Nakai (Jaran-cho; Labiatae). This compound was obtained as white plate-like crystal and named as Jaranidoside. It has a molecular formula $C_{17}H_{26}O_{12}$ and mp $128{\sim}130^{\circ}C$. The structure of the Jaranidoside was assumed from data of chemical reactions and PMR specturum of the compound. To determine the most favorable conformation, informations on the proton coupling and chemical shift were used. Jaranidoside exhibited a stimulating activity on smooth muscle and cardiac muscle. No antimicrobial activity on five microorganism strains was observed.

• Molecules and Cells
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• v.39 no.1
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• pp.20-25
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• 2016

Photosynthesis is a highly robust process allowing for rapid adjustment to changing environmental conditions. The efficient acclimation depends on balanced redox metabolism and control of reactive oxygen species release which triggers signaling cascades and potentially detrimental oxidation reactions. Thiol peroxidases of the peroxiredoxin and glutathione peroxidase type, and ascorbate peroxidases are the main peroxide detoxifying enzymes of the chloroplast. They use different electron donors and are linked to distinct redox networks. In addition, the peroxiredoxins serve functions in redox regulation and retrograde signaling. The complexity of plastid peroxidases is discussed in context of suborganellar localization, substrate preference, metabolic coupling, protein abundance, activity regulation, interactions, signaling functions, and the conditional requirement for high antioxidant capacity. Thus the review provides an opinion on the advantage of linking detoxification of peroxides to different enzymatic systems and implementing mechanisms for their inactivation to enforce signal propagation within and from the chloroplast.

• Bulletin of the Korean Chemical Society
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• v.21 no.10
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• pp.1039-1040
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• 2000

The water-soluble poly(methoxyethoxy-aminoarlyoxy phosphazene) has been synthesized and investigated as a polymeric carrier molecule for the covalent attachment of bioactive agents. The synthetic procedures were developed first through the use of cyclic trimeric model systems. These model systems were utilized for the synthesis of polymeric analogues containing bioactive side groups. The sodium salts of 2-methoxyethanol and 4-acetamidophenol were allowed to react with $(NPCl_2)_3$ or $(NPCl_2)n$ or to yield derivatives of type $[NP-(OCl_2CH_2CH_2OCH_3){\chi}(OArNHCOCH_3)y]_3or$ n. The 4-acetamido groups were then hydrolyzed to 4-amino-phenoxy units with potassium tert-butoxide. Coupling reactions between amino group and N-acetylglycine was accomplished with the use of dicyclohexylcarbodiimide. Their properties and structural characterization are discussed.

• Bulletin of the Korean Chemical Society
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• v.22 no.11
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• pp.1243-1247
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• 2001

The water-soluble poly(aminoaryloxy-methylamino phosphazene) has been synthesized and investigated as a polymeric carrier species for the covalent attachment of biologically active agents. The cyclic trimeric model systems were utilized for the synthesis of polymeric analogues containing bioactive side groups. The sodium salt of 4-acetamidophenol was first allowed to react with (NPCl2)3 or (NPCl2)n and was then treated with excess methylamine to yield derivatives of type [NP(NHCH3)x(OArNHCOCH3)y]3 or [NP(NHCH3)x(OArNHCOCH3)y]n. The 4-acetamido groups were then hydrolyzed to 4-aminophenoxy units with potassium tert-butoxide. Coupling reactions between amino group and N-acetylglycine was accomplished with the use of dicyclohexylcarbodiimide. Their properties and structural characterization are discussed.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.568-572
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• 1989

Terphenyl dialdehyde 6 was obtained in 17.4% overall yield through oxidative coupling, methylation, and bisformylation reactions starting from p-cresol, and then coupled intermolecularly using McMurry reaction to give 22-membered macrocylic host 7 in 14.4% yield. In crystal structure host 7 has $C2_v$ symmetry with cis-cis configuration of two double bonds. Four methoxy groups adjacent to double bonds and the other two methoxy groups are directed opposite side, forming a cavity which can nest a guest. The cavity is filled by two inward-turned methyl groups out of four methoxy groups adjacent to double bonds. The kinetically controlled reaction mechanism leading to cis product was proposed. The cation binding properties of 7 were obtained using picrate extraction experiment from $D_2O\; into\; CDCl_3\; at\; 25^{\circ}C$. All the spherical cations (from $Li^+ to NH4^+)$ are complexed with free energies of $7.3{\pm}0.3$ kcal/mol.