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RISS 인기검색어
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- 저자 : ( Dahye Baik ) (검색결과 3 건)
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Kim, Yechan,Kim, Seoung-Tae,Kang, Dahye,Sohn, Te-ik,Jang, Eunyoung,Baik, Mu-Hyun,Hong, Sungwoo Royal Society of Chemistry 2018 Chemical Science Vol.9 No.6
<▼1><P>A new, bidentate, chiral directing group derived from 2,2-dimethyl-1-(pyridin-2-yl)propan-1-amine was discovered, which enables stereoselective palladium(<SMALL>II</SMALL>)-catalyzed intramolecular C(sp<SUP>3</SUP>)–O bond formation.</P></▼1><▼2><P>The systematic investigation of chiral bidentate auxiliaries has resulted in the discovery of a chiral 2,2-dimethyl-1-(pyridin-2-yl)propan-1-amine-derived directing group that enables stereoselective palladium(<SMALL>II</SMALL>)-catalyzed intramolecular C(sp<SUP>3</SUP>)–O bond formation. This new chiral directing group exhibited high reactivity in the activation of methylene C(sp<SUP>3</SUP>)–H bonds with excellent levels of stereoselectivity (a diastereomeric ratio of up to 39 : 1), which allowed the construction of a wide range of oxaspirocycles. Mechanistic investigations were also conducted to elucidate the reaction mechanism and understand the origin of the diastereoselectivity. DFT calculations suggest that only modest levels of diastereoselectivity are accomplished at the rate-determining C–H metalation–deprotonation step and the d.r. is further enriched at the reductive elimination step.</P></▼2>
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Room-Temperature Ring-Opening of Quinoline, Isoquinoline, and Pyridine with Low-Valent Titanium
Baek, Seung-yeol,Kurogi, Takashi,Kang, Dahye,Kamitani, Masahiro,Kwon, Seongyeon,Solowey, Douglas P.,Chen, Chun-Hsing,Pink, Maren,Carroll, Patrick J.,Mindiola, Daniel J.,Baik, Mu-Hyun American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.36
<P>The complex (PNP)Ti=(CHBu)-Bu-t((CH2Bu)-Bu-t) (PNP = N[2-P(i)p(r2)-4-methylphenyl](2-)) dehydrogenates cyclohexane to cyclohexene by forming a transient low-valent titanium-alkyl species, [(PNP)Ti((CH2Bu)-Bu-t)], which reacts with 2 equiv of quinoline (Q) at room temperature to form (H3CBu)-Bu-t and a Ti(IV) species where the less hindered C-2=N-1 bond of Qis ruptured and coupled to another equivalent of Q, The product isolated from this reaction is an imide with a tethered cycloamide group, (PNP)Ti=N[C18H13N] (1). Under photolytic conditions, intramolecular C-H bond activation across the imide moiety in 1 occurs to form 2, and thermolysis reverses this process. The reaction of 2 equiv of isoquinoline (Iq) with intermediate [(PNP)Ti((CH2Bu)-Bu-t)] results in regioselective cleavage of the C-I=N-2 and C-1-H bonds, which eventually couple to form complex 3, a constitutional isomer of 1. Akin to 1, the transient [(PNP)Ti((CH2Bu)-Bu-t)] complex can ring-open and couple two pyridine molecules, to produce a close analogue of 1, complex (PNP)Ti=N[C10H9N] (4). Multinudear and multidimensional NMR spectra confirm structures for complexes 1-4, whereas solid-state structural analysis reveals the structures of 2, 3, and 4. DFT calculations suggest an unprecedented Mechanism for ring-opening of Q wheat the reactive intermediate in the low-spin manifold crosses over to the high-spin surface to access a low-energy transition state but returns to the low-spin surface immediately. This double spin-crossover constitutes a rare example of a two-state reactivity, which is key for enabling the reaction at room temperature. The regioselective behavior of Iq ring-opening is found to be due to electronic effects, where the aromatic resonance of the bicycle is maintained during the key C-C coupling event.</P>
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( Gwang Hyeon Choi ),( Eun Sun Jang ),( Young Seok Kim ),( Youn Jae Lee ),( In Hee Kim ),( Sung Bum Cho ),( Han Chu Lee ),( Jang Jeong Won ),( Moran Ki ),( Hwa Young Choi ),( Dahye Baik ),( Sook-hyang 대한간학회 2020 춘·추계 학술대회 (KASL) Vol.2020 No.1
Aims: This study aimed to elucidate the all-cause mortality and the incidence hepatocellular carcinoma (HCC), and their related factors among the patients with chronic hepatitis C virus (HCV) infection in South Korea. Methods: A total 2,369 patients with HCV RNA positivity and no HCC at diagnosis (mean age 57.5 years, 47.6% male, 29.8% cirrhosis) were prospectively enrolled in 6 university hospitals from May 2007 to March 2019 and followed until February 2020. The patients were classified into untreated group (n=753, 31.8%), interferon (IFN)-based treated group (n=698, 29.5%), and direct-acting antivirals (DAA)-treated group (n=918, 38.8%). Kaplan-Meier curve analysis and Cox regression analysis were performed. Results: During 4.3 years (IQR 2.5-7.6) of median follow-up, 245 patients died and 147 developed HCC. The 3-, 5-, and 10-year cumulative mortality in the HCV patients was 4.6%, 8.0%, and 12.8%, respectively. The 3-, 5-, and 10-year cumulative incidence of HCC was 4.5%, 8.5%, and 18.3%, respectively. The SVR rate was 68.7% in IFN-based treated group and 95.2% in DAA-treated group, by per-protocol analysis. After multivariate analysis, achievement of SVR was an independent factor for decreased risk of HCC (adjusted hazard ratio [aHR] 0.22, 95% confidence interval [CI] 0.12-0.39, P<0.001 for IFN based-treated group and aHR 0.29, 95% CI 0.17-0.50, P<0.001 for DAA-treated group, respectively). SVR was an independent factor for decreased risk of all cause of mortality (aHR 0.27, 95% CI 0.17-0.44, P<0.001 for IFN based-treated group and aHR 0.23, 95% CI 0.12-0.45, P<0.001 for DAA-treated group, respectively) along with other factors. Conclusions: In Korea HCV cohort, 5-year cumulative incidence of HCC and mortality was 8.0% and 8.5%, respectively. The overall treatment rate was 70% with overall SVR rate of 86%. Achievement of SVR was a strong factor for better outcomes, which support active screening and treatment of HCV infection.
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