Jong Hwan Kwak
Sungkyunkwan University
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Featured researches published by Jong Hwan Kwak.
Organic Letters | 2011
Jihye Park; Eonjeong Park; Aejin Kim; Youngil Lee; Ki-Whan Chi; Jong Hwan Kwak; Young Hoon Jung; In Su Kim
A rhodium-catalyzed oxidative acylation of benzamides with aryl aldehydes via direct sp(2) C-H bond cleavage is described. In the presence of [Cp*RhCl(2)](2), AgSbF(6), and silver carbonate as an oxidant, N,N-diethyl benzamides can be effectively carbonylated to yield ortho-acyl benzamides.
Journal of Organic Chemistry | 2015
Jihye Park; Neeraj Kumar Mishra; Satyasheel Sharma; Sangil Han; Youngmi Shin; Taejoo Jeong; Joa Sub Oh; Jong Hwan Kwak; Young Hoon Jung; In Su Kim
The rhodium(III)-catalyzed direct allylation of indolines with allylic carbonates at room temperature is described. These transformations provide the facile and efficient construction of C7-allylated indolic scaffold.
Archives of Pharmacal Research | 2009
Jong Hwan Kwak; Hyun-Jung Kim; Kwang Ho Lee; Se Chan Kang; Ok Pyo Zee
Eight iridoid glycosides and four phenolic compounds were isolated from the EtOAc soluble fraction of Veronica peregrina MeOH extract as the radical scavengers for antioxidant activity. The compounds were identified as protocatechuic acid (1), luteolin (2), veronicoside (3), minecoside (4), specioside (5), amphicoside (6), catalposide (7), 6-O-cis-p-coumaroyl catalpol (8), p-hydroxy benzoic acid methyl ester (9), verproside (10), verminoside (11), and chrysoeriol 7-glucuronide (12) by spectroscopic analysis. All compounds except for 1 and 2 were isolated for the first time from this plant. The antioxidant activity was evaluated by the ORAC(Oxygen Radical Absorbance Capacity) assay, which measures scavenging activity against peroxy radicals induced by 2,2′-azobis (2-methoxypropion-amidine) dihydrochloride, and the ORAC value is expressed as relative trolox equivalent. Compounds 2, 4, 5, 6, 8, and 12 exhibited potent antioxidant activity, and compounds 1, 11 had similar activity with trolox, whereas the other compounds showed weaker activity than trolox.
Journal of Organic Chemistry | 2014
Sangil Han; Satyasheel Sharma; Jihye Park; Mirim Kim; Youngmi Shin; Neeraj Kumar Mishra; Jong Jin Bae; Jong Hwan Kwak; Young Hoon Jung; In Su Kim
A palladium-catalyzed oxidative coupling of arene C-H bonds with benzylic ethers via C-H bond activation is described. The reaction proceeds efficiently with a broad range of substrates bearing conventional directing groups with excellent functional group compatibility. This protocol potentially provides opportunities to use dibenzyl ethers as new acyl equivalents for catalytic acylation reactions.
Archives of Pharmacal Research | 2009
Jong Hwan Kwak; Min Woo Kang; Jong Hwa Roh; Sang Un Choi; Ok Pyo Zee
Cytotoxicity-guided fractionation and purification of MeOH extract from Chionanthus retusus Lindl. et Paxton resulted in the isolation of compounds. Fourteen phenolic compounds were isolated from the EtOAc soluble fraction, and their structures were determined by spectroscopic analysis. Isolated compounds were identified as phillygenin (1), scopoletin (2), pinoresinol (3), kaempferol (4), aromadendrin (5), 2-(4-hydroxyphenyl)ethanol (6), 3,3′,5,5′,7-pentahydroxyflavanone (7), luteolin (8), quercetin (9), apigenin (10), chrysoeriol (11), phillyrin (12), oleuropein (13), (7R,8R)-guaiacylglycerol (14). All compounds except for 12 and 13 were isolated for the first time from this plant and genus Chionanthus. Anti-proliferative effect of isolated compounds were evaluated by the sulforhodamin B assay against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15). Compounds 4 and 8–10 were significantly active with ED50 values of 1.84–6.35 μg/mL. Also, compounds 1, 3, 5 and 7 revealed cytotoxic effects at concentrations below 30 μg/mL.
Organic and Biomolecular Chemistry | 2013
Mirim Kim; Jihye Park; Satyasheel Sharma; Sangil Han; Sang Hoon Han; Jong Hwan Kwak; Young Hoon Jung; In Su Kim
Tandem rhodium-catalyzed oxidative allylation and annulation of acetanilides with allyl acetate to afford the corresponding indoles are described. In addition, the site-selective C2 allylation, crotylation and prenylation of indoles using allylic acetates under rhodium catalysis are reported.
Archives of Pharmacal Research | 2008
Se Chan Kang; Chang Min Lee; Eui Su Choung; Jong Phil Bak; Jong Jin Bae; Hyun Sook Yoo; Jong Hwan Kwak; Ok Pyo Zee
The Rheum palmatum L., a traditional medicine in Korea, was screened for their estrogenic activity in a recombinant yeast system with a human estrogen receptor (ER) expression plasmid and a reporter plasmid used in a previous study. The EC50 values of the n-hexane, dichloromethane, ethyl acetate, n-butanol, and water fractions of the methanolic extract of R. palmatum in the yeast-based estrogenicity assay system were 0.145, 0.093, 0.125, 1.459, 2.853 µg/mL, respectively, with marked estrogenic activity in the dichloromethane fraction. Using an activity-guided fractionation approach, five known anthraquinones, chrysophanol (1), physcion (2), emodin (3), aloe-emodin (4) and rhein (5), were isolated from the dichloromethane fraction. Compound 3 had the highest estrogenic relative potency (RP, 17bestradiol = 1.00) (6.3 × 10−2), followed by compound 4 (3.8 × 10−3), compound 5 (2.6 × 10−4), a compound 1 (2.1 × 10−4). Also, compound 3 and fraction 3 (which contained compound 3) of the dichloromethane fraction of R. palmatum showed strong cytotoxicity in both ER-positive (MCF-7) and-negative (MDA-MB-231) breast cancer cell lines.
Organic Letters | 2016
Taejoo Jeong; Sang Hoon Han; Sangil Han; Satyasheel Sharma; Jihye Park; Jong Suk Lee; Jong Hwan Kwak; Young Hoon Jung; In Su Kim
The rhodium(III)-catalyzed direct C-H functionalization of azobenzenes with ethyl glyoxalate and aryl glyoxals is described. This protocol provides the facile and efficient formation of various C3-acylated-(2H)-indazoles in moderate to high yields.
International Immunopharmacology | 2014
Hyun Jung Koo; Weon-Jong Yoon; Eun-Hwa Sohn; Young-Min Ham; Seon-A Jang; Jung-Eun Kwon; Yong Joon Jeong; Jong Hwan Kwak; Eunsoo Sohn; Soo-Young Park; Ki-Hyo Jang; Seung Namkoong; Hyo-Sang Han; Yong-Hwan Jung; Se Chan Kang
Fruits of the Litsea family of trees and shrubs contain biologically active compounds, some of which have been used as natural nutrients and flavoring agents in food. In this study, we identified novel anti-nociceptive effects of the 30% ethanol extract, the CH(2)Cl(2) fraction and the associated active components (Hamabiwalactone A and B) from Litsea japonica fruit by using in vivo peripheral and central nervous pain models. In addition, we compared the anti-inflammatory effects of several fractions from L. japonica fruit extracts using lipopolysaccharide (LPS)-stimulated Raw264.7 cells. The CH(2)Cl(2) fraction of L. japonica fruit (LJM) had an optimal combination of anti-inflammatory effects and low cytotoxicity. Dose response studies were performed to determine the inhibitory effects of LJM on the pro-inflammatory enzymes, COX-2/PGE(2) and NO/iNOS, and pro-inflammatory cytokines, IL-1β, IL-6, and TNF-α. Molecular profiling revealed that LJM exerts anti-inflammatory effects through inhibition of NF-κB and JNK/p38 MAPK signaling in LPS-induced macrophages. This study suggests that CH2Cl2 fraction of L. japonica fruit and its bioactive components are potential candidates as anti-inflammatory and analgesic agents (painkillers) for the treatment of inflammatory diseases.
Journal of Organic Chemistry | 2015
Taejoo Jeong; Sangil Han; Neeraj Kumar Mishra; Satyasheel Sharma; Seok-Yong Lee; Joa Sub Oh; Jong Hwan Kwak; Young Hoon Jung; In Su Kim
The rhodium(III)-catalyzed direct amidation of indoles and pyrroles with aryl and alkyl isocyanates is described. These transformations provide a facile and efficient construction of C2-amidated N-heterocyclic scaffolds.