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181.
Ridge Michael P. Ylagan Eric Jaewon Lee Dr. Daniela E. Negru Dr. Paolo Ricci Bohyun Park Haram Ryu Prof. Dr. Mu-Hyun Baik Prof. Dr. P. Andrew Evans 《Angewandte Chemie (International ed. in English)》2023,62(23):e202300211
An enantioselective rhodium(I)-catalyzed Pauson–Khand reaction (PKR) using 1,6-chloroenynes that contain challenging 1,1-disubstituted olefins is described. In contrast to the previous studies with these types of substrates, which are only suitable for a single type of tether and alkyne substituent, the new approach results in a more expansive substrate scope, including carbon and heteroatom tethers with polar and non-polar substituents on the alkene. DFT calculations provide critical insight into the role of the halide, which pre-polarizes the alkyne to lower the barrier for metallacycle formation and provides the proper steric profile to promote a favorable enantiodetermining interaction between substrate and chiral diphosphine ligand. Hence, the chloroalkyne enables the efficient and enantioselective PKR with 1,6-enynes that contain challenging 1,1-disubstituted olefins, thereby representing a new paradigm for enantioselective reactions involving 1,6-enynes. 相似文献
182.
Gunjoo Kim Seung-Hee Ryu Hojin Jeong Yunji Choi Seungwoo Lee Joon-Hwan Choi Hyunjoo Lee 《Angewandte Chemie (International ed. in English)》2023,62(30):e202306017
Inducing strong metal-support interaction (SMSI) has been a useful way to control the structure of surface active sites. The SMSI often causes the encapsulation of metal particles with an oxide layer. Herein, an amorphous ceria shell was formed on Cu nanoparticles under a mild gas condition with high activity and durability for surface reaction. Cu−Ce solid solution promoted the transfer of surface oxygen species, which induced the ceria shell formation on Cu nanoparticles. This catalyst was used for CO2 hydrogenation, selectively producing CO with high low-temperature activity and good durability for operation at high temperature. CO2 activation and H2 spillover could occur at low temperatures, enhancing the activity. The shell prevented the sintering, assuring durability. This catalyst was applied to a bench-scale reactor without loss in performance, resulting in high CO productivity in all temperature ranges. 相似文献
183.
Mycobacterial phenolic glycolipid virulence factor biosynthesis: mechanism and small-molecule inhibition of polyketide chain initiation 总被引:1,自引:0,他引:1
Phenolic glycolipids (PGLs) are polyketide-derived virulence factors produced by Mycobacterium tuberculosis, M. leprae, and other mycobacterial pathogens. We have combined bioinformatic, genetic, biochemical, and chemical biology approaches to illuminate the mechanism of chain initiation required for assembly of the p-hydroxyphenyl-polyketide moiety of PGLs. Our studies have led to the identification of a stand-alone, didomain initiation module, FadD22, comprised of a p-hydroxybenzoic acid adenylation domain and an aroyl carrier protein domain. FadD22 forms an acyl-S-enzyme covalent intermediate in the p-hydroxyphenyl-polyketide chain assembly line. We also used this information to develop a small-molecule inhibitor of PGL biosynthesis. Overall, these studies provide insights into the biosynthesis of an important group of small-molecule mycobacterial virulence factors and support the feasibility of targeting PGL biosynthesis to develop new drugs to treat mycobacterial infections. 相似文献
184.
Bong YS Lee KS Shin WJ Ryu JS 《Rapid communications in mass spectrometry : RCM》2008,22(18):2809-2812
We have analyzed the oxygen and hydrogen isotopic composition of juices from fruits and vegetables collected from a small orchard in order to investigate the differences in isotopic enrichment and evaporation intensity between fast-growing vegetables and slow-growing fruits grown under the same climatic conditions. The oxygen and hydrogen isotope levels were much higher in the juices of the fruits and vegetables than in the source waters in which they grew because of evaporation effects. According to our data, fast-growing vegetables are subject to greater evaporation than slow-growing fruits. An evaporation experiment using the source water showed that the oxygen and hydrogen isotopic composition of the 60-80% residual fraction was similar to that of the isotopically enriched grape juice, whereas those of the plume and tomato juices were very close to that of the 80-90% residual fraction, thus proving the effect of evaporation. Copyright (c) 2008 John Wiley & Sons, Ltd. 相似文献
185.
P. Gasik K. Piasecki N. Herrmann Y. Leifels T. Matulewicz A. Andronic R. Averbeck V. Barret Z. Basrak N. Bastid M. L. Benabderrahmane M. Berger P. Buehler M. Cargnelli R. Čaplar P. Crochet O. Czerwiakowa I. Deppner P. Dupieux M. Dželalija L. Fabbietti Z. Fodor I. Gašparić Y. Grishkin O. N. Hartmann K. D. Hildenbrand B. Hong T. I. Kang J. Kecskemeti Y. J. Kim M. Kirejczyk M. Kiš P. Koczon R. Kotte A. Lebedev A. Le Fèvre J. L. Liu X. Lopez V. Manko J. Marton R. Münzer M. Petrovici F. Rami A. Reischl W. Reisdorf M. S. Ryu P. Schmidt A. Schüttauf Z. Seres B. Sikora K. S. Sim V. Simion K. Siwek-Wilczyńska V. Smolyankin K. Suzuki Z. Tymiński P. Wagner I. Weber E. Widmann K. Wiśniewski Z. G. Xiao I. Yushmanov Y. Zhang A. Zhilin V. Zinyuk J. Zmeskal 《The European Physical Journal A - Hadrons and Nuclei》2016,52(6):177
186.
Jeong GT Lee KM Yang HS Park SH Park JH Sunwoo C Ryu HW Kim D Lee WT Kim HS Cha WS Park DH 《Applied biochemistry and biotechnology》2007,137(1-12):935-946
Hydrogels are materials with the ability to swell in water through the retention of significant fractions of water within their structures. Owing to their relatively high degree of biocompatibility, hydrogels have been utilized in a host of biomedical applications. In an attempt to determine the optimum conditions for hydrogel synthesis by the free-radical polymerization of sorbitan methacrylate (SMA), the hydrogel used in this study was well polymerized under the following conditions: 50% (w/v) SMA as monomer, 1% (w/w) alpha, alpha'-azo-bis(isobutyro-nitrile) as thermal initiator, and 1% (w/w) ethylene glycol dimethacrylate as cross-liking agent. Under these conditions, the moisture content of the polymerized SMA hydrogel was higher than in the other conditions. Moreover, the moisture content of the poly(SMA) hydrogel was also found to be higher than that of the poly(methyl methacrylate [MMA]) hydrogel. When the Fourier transform-infrared spectrum of poly(SMA) hydrogel was compared with that of poly(MMA) hydrogel, we noted a band at 1735-1730/cm, which did not appear in the Fourier transform-infrared spectrum of poly(MMA). The surface of the poly(SMA) hydrogel was visualized through scanning electron microscopy, and was uniform and clear in appearance. 相似文献
187.
188.
Four different Ni/YSZ cermets were prepared by combining two sets of NiO and YSZ powders of different size. The microstructural
change evolved during the course of electrode adhesion and cell operation was monitored using scanning electron microscopy
(SEM) and energy dispersive spectroscopy (EDS). The anodic activity was compared by analyzing the ∝ impedance spectra of four
Ni/YSZ cermet (H2) / YSZ half cells at 1000 °C. Among the cermets, the one that prepared from the smaller NiO and larger YSZ powder showed
the best anodic performances on aspects of the initial activity and long-term stability. This favorable performance is partly
responsible to the presence of larger YSZ particles which provide a supporting matrix to suppress the microstructural change
against Ni sintering and concomitant volume shrinkage, and partly to an easy formation of Ni channel for electronic conduction.
Anodic performances of the other cermets were also discussed based on their microstructure. 相似文献
189.
190.
Synthesis and radical polymerization of methacrylate endowed with bicyclobis(γ‐butyrolactone) moiety through methylene linker 下载免费PDF全文
Ryu Yamasaki Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2015,53(21):2462-2468
A series of methacrylates bearing bicyclobis(γ‐butyrolactone) (BBL) moiety were synthesized and radically polymerized to afford the corresponding poly(methacrylate)s bearing BBL moiety in the side chain, with expecting that the high polarity and rigidity of BBL would be inherited by the polymers. The resulting polymers were soluble in polar aprotic solvents such as dimethyl sulfoxide and N,N‐dimethylformamide because of the high polarity of the BBL moiety. The glass transition temperatures (Tg) of the polymers depended on the length of methylene linker that tethered the methacrylate and BBL moieties, making the use of shorter linkers lead to higher Tgs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2462–2468 相似文献