• Bulletin of the Korean Chemical Society
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• v.31 no.3
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• pp.735-738
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• 2010

• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.777-782
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• 2007

A novel library of amino-substituted 2-pyridones has been constructed through a two-step sequence of microwave-promoted Buchwald-Hartwig amination of 2-benzyloxy halopyridines followed by debenzylation. Microwave-promoted amination of 3- or 4-halopyridine in the presence of a suitable palladium catalyst and ligand system provided amino-substituted 2-benzyloxypyridines in excellent yields. Then, debenzylation of 2- benzyloxypyridines afforded the corresponding 2-pyridones with high efficiency.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.249-252
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• 2004

Cytochrome P450 (P450)/$O_2$/NADPH engender electron transfer reaction of N-benzyl-N-substituted benzylamines to yield corresponding radical cation 1 that is simultaneously converted into 2 and 3. Subsequently, expulsion of proton and hydroxylation yielding a-hydroxylamines are followed by formation of benzaldehydes and benzylamines.

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.252-255
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• 1992

Preparative methods for and catalytic activities of monoaza-18-crown-6 or monoaza-15-crown-5 in the reaction of 1-bromooctane with aqueous KI or NaI were investigated. Monoazacrown ethers were prepared by debenzylation of N-benzylmonoazacrown ethers, obtained from the reaction of N-benzyldiethanolamine and oligoethylene glycol ditosylate. The phase-transfer catalytic activity of N-benzylmonoazacrown ethers was higher than that of the corresponding monoazacrown ethers.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.289-292
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• 2004

A trisaccharide, GlcNAcp- ${\beta}-(1{\to}3)-Galp-{\alpha}-(1{\to}2)$-6-deoxy-altroHepp- ${\alpha}-(1{\to}O$-propyl, as an O-antigenic repeating unit of C. jejuni serotype O:23 and O:36 was synthesized. Coupling of the GlcNPhth-(1${\to}$3)-Gal disaccharide donor with allyl 6-deoxy-altroHep acceptor in the presence of iodonium dicollidine perchlorate (IDCP) promoter afforded the ${\alpha}$-galactosidic trisaccharide with high stereoselectivities. Subsequent deacetalation, dephthaloylation, N-acetylation, and hydrogenolytic debenzylation furnished the title compound.

• Polymer(Korea)
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• v.33 no.2
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• pp.158-163
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• 2009

In this study, we synthesized a series of dendritic polystyrene-b-linear poly (t-butyl acrylate) copolymers with well-defined molecular architectures. The hydroxyl group located at the focal point of the second generation dendron bearing polystyrene ($M_n$ = 1000 g/mol) peripheries was converted into amine group via the following stepwise reactions: 1) tosylatoin, 2) azidation, and 3) reduction. On the other hand, the linear poly (t-butyl acrylate)s were prepared by an atom transfer radical polymerization (ATRP) of t-butyl acrylate where benzyl 2-bromopropanoate and Cu(I)Br/PMDETA were used as initiator and catalyst, respectively. To convert the end group of prepared poly (t-butyl acrylate) s into carboxylic acid, a debenzylation was performed using Pd/C catalyst under $H_2$ atmosphere. In the final step, dendritic-linear block copolymers were obtained through a simple amide coupling reaction mediated by 4-(dimethylamino) pyridine(DMAP) and N,N'-diisopropylcarbodiimide(DIPC). The resulting diblock copolymers were shown to have well-defined molecular weights and narrow molecular weight distributions as supported by $^1H$-NMR spectroscopy and gel permeation chromatography(GPC).

• Macromolecular Research
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• v.12 no.4
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• pp.359-366
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• 2004

The polysaccharide, (1\longrightarrow5)-$\alpha$-D-ribofuranan, was synthesized by a cationic ring-opening polymerization of 1,4-anhydro-2,3-di-O-benzyl-$\alpha$-D-ribopyranose with the aid of boron trifluoride etherate and subsequent debenzylation. This polysaccharide catalyzed the hydrolysis of ethyl p-nitrophenyl phosphate, uridylyl(3'\longrightarrow5')uridine ammonium salt, and 4-tert-butylcatechol cyclic phosphate N-methyl pyridinium. The polymer also catalyzed the cleavage of nucleic acids (DNA and RNA). The hydrolysis of ethyl p-nitrophenyl phosphate in the presence of the polymer was accelerated by 1.5 ${\times}$ 10$^3$ times relative to the uncatalyzed reaction. The catalytic activity was attributable to the vic-cis-diols of the riboses being located inside the active center that is formed by polymer chain folding; these diols form hydrogen bonds with two phosphoryl oxygen atoms of the phosphates so as to activate the phosphorus atoms to be attacked by nucleophile ($H_2O$).

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.174-178
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• 2013

A highly reliable dealkylation protocol of alkyl aryl ethers, whose alkyl groups are longer than methyl group, has been developed. We report that various ethyl, n-propyl, and benzyl aryl ethers are successfully cleaved using an ionic liquid, 1-n-butyl-3-methylimidazolium bromide, [bmim][Br], under microwave irradiation. Despite many characteristics such as lower cost and less toxicity of the alkylating agents, and greater hydrophobicity of the products, longer alkyl ethers have been significantly less exploited than methyl ethers, probably due to more difficulty in the deprotection step. Since it has the same advantages as the demethylation method developed by this group including mild conditions, short reaction time, and small use of the ionic liquids, the dealkylation protocol can greatly encourage the broader use of longer alkyl groups in the protection of phenolic groups. As with our previous study of demethylation using [bmim][Br], the microwave irradiation is crucial for the deprotection of longer alkyl aryl ethers. Unlike the conventional heating, which causes either low conversion or decomposition, the microwave irradiation seems to more effectively provide energy to cleave the ether bonds and therefore suppresses the undesired reactions.

• Environmental Mutagens and Carcinogens
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• v.22 no.3
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• pp.169-174
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• 2002

Resveratrol is known to have potent cancer chemopreventive activity against tumorigenesis caused by 7,12-dimetylbenz［$\alpha$］anthracene(DMBA) which is known to be oxidized to reactive products by cytochrome P450 1B1 (CYP1B1). The effects of resveratrol on the activity of recombinant human P450 1 family enzymes, expressed in Escherichia coli membranes with human NADPH-P450 reductase, were determined by measuring alkoxyresorufin O-dealkylation activity, e.g., ethoxyresorufin O-deethylation (EROD) CYP1A1, methoxyresorufin O-demethylation (MROD), CYP1A2, benzyloxyresorufin-O-debenzylation (BROD), CTP1B1. Resveratrol inhibited CYP1B1 and CYP1A1 activities in a dose-dependent manner with $IC_{50}$/ values of 59 and 10$\mu$M for EROD activity and 1.8 and 30$\mu$M for BROD activity, respectively. Resveratrol had only weak inhibitory effect on CYP1A2 activity ($IC_{50}$/ values of 0.44 mM for EROD and ＞2 mM for MROD). Furthermore, resveratrol did not affect NADPH-P450 reductase activity significantly. Resveratrol inhibited the CYP1B1-dependent EROD activity with a $K_{i}$ of 28 $\mu$M in a non-competitive type manner. these results suggest that resveratrol-derived inhibited of CYP1B1 and CYP1A1 activities may contribute to the suppression of DMBA inducible tumorigenesis observed in extrahepatic tissues.s.

• YAKHAK HOEJI
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• v.44 no.2
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• pp.141-148
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• 2000

A new synthetic method of 6-(1-oxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones was developed, 2-formyl-1,4,5,8-tetramethoxynaphthalene was oxidized to form 6-formyl-5,8-dimethoxy-1,4-naphthoquinone(DMNQ). This was selectively reduced and benzylated to produce 6-formyl-5,8-dimethoxy-1,4-dibenzyloxynaphthalene, to which various alkylmagnesium halide were added, followed by debenzylation and oxidation in sequence, yielding 6-(1-hydroxyalkyl)-DMNQ derivatives. 6-(1-hydroxyalkyl)-5,8-diethoxy-1,4-naphthalene (DENQ) derivatives were synthesized by similar procedure. 1'-OH of the naphthoquinone derivatives was acylated with various alkanoic acids to give 6-(1-acyloxyalkyl)-DMNQ or DENQ derivatives. TOPO-I inhibitory activity and cytotoxicity of DENQs were less potent than that of DMNQs. Among the DMNQ and DENQ analogues, the ones with alkyl group being heptyl were most potent in TOPO-I inhibition $IC_{50}$/; 30.1, 36.4 $\mu$M). DUNQ derivatives with a longer side chain exhibited a weaker cytotoxicity. A correlation between size of the alkyl side chain and cytotoxicity was not observed for DENQ derivatives. Acylation of 1'-hydroxyl group, in general, decreased both TOPO-I inhibitory activity and cytotoxicity T/C (%) values of the DENQ derivatives on S-180 intraperitoneal tumor were larger than those of DMNQ derivatives. Among the compounds synthesized,6-(1-hydroxyheptyl)-DENQ and 6-(1-hex-anoyloxyoctyl)-DMNQ showed the highest T/C values of 183% and 182%, respectively.