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161.
Pter Nagy Hisanori Ueki Dmitrii O. Berbasov Vadim A. Soloshonok 《Journal of fluorine chemistry》2008,129(5):409-415
Kinetic study of the triethylamine (TEA)-catalyzed isomerization of imine, derived from benzylamine and trifluoroacetophenone to the corresponding N-benzylidene-2,2,2-trifluoro-1-(phenyl)ethylamine has revealed concerted nature of the mechanism of this reaction via a virtually unionized transition state. As a synthetic bonus of this kinetic study, we found that application of a polar solvent (acetonitrile) and four equivalents of TEA provide for optimal reaction conditions at high concentrations. We demonstrate that application of these reaction conditions allows to substantially increase the reaction rates, chemical yields and results in cleaner formation of the target products. 相似文献
162.
Dr. Yuting Jin Prof. Enze Zhou Prof. Toshiyuki Ueki Prof. Danni Zhang Prof. Yongqiang Fan Prof. Dake Xu Prof. Fuhui Wang Prof. Derek R. Lovley 《Angewandte Chemie (International ed. in English)》2023,62(38):e202309005
Electrobiocorrosion, the process in which microbes extract electrons from metallic iron (Fe0) through direct Fe0-microbe electrical connections, is thought to contribute to the costly corrosion of iron-containing metals that impacts many industries. However, electrobiocorrosion mechanisms are poorly understood. We report here that electrically conductive pili (e-pili) and the conductive mineral magnetite play an important role in the electron transfer between Fe0 and Geobacter sulfurreducens, the first microbe in which electrobiocorrosion has been rigorously documented. Genetic modification to express poorly conductive pili substantially diminished corrosive pitting and rates of Fe0-to-microbe electron flux. Magnetite reduced resistance to electron transfer, increasing corrosion currents and intensifying pitting. Studies with mutants suggested that the magnetite promoted electron transfer in a manner similar to the outer-surface c-type cytochrome OmcS. These findings, and the fact that magnetite is a common product of iron corrosion, suggest a potential positive feedback loop of magnetite produced during corrosion further accelerating electrobiocorrosion. The interactions of e-pili, cytochromes, and magnetite demonstrate mechanistic complexities of electrobiocorrosion, but also provide insights into detecting and possibly mitigating this economically damaging process. 相似文献
163.
Sato Y Hayashi H Okazaki M Aso M Karasawa S Ueki S Suemune H Koga N 《Magnetic resonance in chemistry : MRC》2008,46(11):1055-1058
5-Uridine derivative carrying a TEMPO radical (UST) was prepared and its single strand (ssUST) and a double strand (dsUST) with its complementary strand were obtained. Similarly, single strands carrying two and five radicals (ssUST2 and ssUST5, respectively) and the corresponding double strands (dsUST2 and dsUST5) were prepared. Their electron paramagnetic resonance (EPR) spectra showed typical anisotropic broadening in the high field line. The rotational correlation times, tau(R), estimated by analyzing the EPR spectra are 1.1 x 10(-10), 5.9 x 10(-10), and 14 x 10(-10) s for UST, ssUSTm, and dsUSTm, respectively. The water-proton relaxivities, r(1) and r(2), at 25 MHz, 0.59 T, and 25 degrees C, also increased in the same order and the r(1) values were 0.26, 0.41, and 0.56 mM(-1) s(-1) for UST, ssUSTm, and dsUSTm, respectively. The r(1) values of 1.00 and 2.06 mM(-1) s(-1) for dsUST2 and dsUST5, respectively, were obtained. 相似文献
164.
Umemura T Ueki Y Tsunoda K Katakai A Tamada M Haraguchi H 《Analytical and bioanalytical chemistry》2006,386(3):566-571
Hexyl methacrylate (HMA)-based monolithic semi-micro columns were prepared by in situ polymerization within the confines of
1.02-mm-i.d. silicosteel tubing for reversed-phase and/or precipitation–redissolution liquid chromatography. Practically useful
monolithic columns with adequate separation efficiency, high permeability, and good mechanical strength were successfully
obtained using a polymerization mixture comprising 24% hexyl methacrylate (HMA), 6% ethylene dimethacrylate (EDMA), 44.5%
1-propanol, and 25.5% 1,4-butanediol. The column performance was evaluated through the separations of a series of alkylbenzenes.
At a normal flow rate of 50 μL min−1, the produced HMA-based monolithic columns typically exhibited 3,000 theoretical plates for a 20-cm-long column, and the
pressure drop was generally less than 1 MPa per 20 cm. The monolithic columns were resistant to at least 15 MPa, and could
be properly operated at 15–20 times higher flow rate than normal, reducing the separation time to 1/15–1/20. The HMA-based
monolithic columns were applied to rapid and efficient separations of proteins such as ribonuclease A, cytochrome c, transferrin,
and ovalbumin in the precipitation–redissolution mode. Using a CH3CN gradient elution at a flow rate of 1,000 μL min−1, four proteins were baseline separated within 20 s. 相似文献
165.
Ueki M Galonić DP Vaillancourt FH Garneau-Tsodikova S Yeh E Vosburg DA Schroeder FC Osada H Walsh CT 《Chemistry & biology》2006,13(11):1183-1191
Four adjacent open reading frames, cytC1-C4, were cloned from a cytotrienin-producing strain of a Streptomyces sp. by using primers derived from the conserved region of a gene encoding a nonheme iron halogenase, CmaB, in coronamic acid biosynthesis. CytC1-3 were active after expression in Escherichia coli, and CytC4 was active after expression in Pseudomonas putida. CytC1, a relatively promiscuous adenylation enzyme, installs the aminoacyl moieties on the phosphopantetheinyl arm of the holo carrier protein CytC2. CytC3 is a nonheme iron halogenase that will generate both gamma-chloro- and gamma,gamma-dichloroaminobutyryl-S-CytC2 from aminobutyryl-S-CytC2. CytC4, a thioesterase, hydrolytically releases the dichloroaminobutyrate, a known streptomycete antibiotic. Thus, this short four-protein pathway is likely the biosynthetic source of this amino acid antimetabolite. This four-enzyme system analogously converts the proS-methyl group of valine to the dichloromethyl product regio- and stereospecifically. 相似文献
166.
Ellis TK Ueki H Yamada T Ohfune Y Soloshonok VA 《The Journal of organic chemistry》2006,71(22):8572-8578
A new generation of modular achiral glycine equivalents have been evaluated with respect to their synthetic utility for the production of tailor-made, sterically constrained alpha-amino acids, which proved to be the most efficient approach developed to date for the synthesis of symmetrical alpha,alpha-disubstituted-alpha-amino acids. Among the new series of achiral glycine equivalents, one was found to be a superior glycine derivative for the Michael additions with various (R)- or (S)-N-(E-enoyl)-4-phenyl-1,3-oxazolidin-2-ones representing a general and practical synthesis of sterically constrained beta-substituted pyroglutamic acids. In particular, the application of these complexes allowed for the preparation of several beta-substituted pyroglutamic acids which include electron-releasing and sterically demanding substituents in the structure thus increasing the synthetic efficiency and expanding the generality of these Michael addition reactions. 相似文献
167.
This paper presents a highly stereoselective synthesis of trifluoro- or difluoromethylated olefins via an S(N)2' type fluorination or reductions of gem-difluorinated vinyloxiranes. Their fluorination with HF-Py furnished trifluoromethylated allylic alcohols with exclusive E selectivity. On the other hand, their reduction with DIBAL-H afforded difluoromethylated E-allylic alcohols predominantly, whereas the corresponding Z isomers were formed exclusively by treatment with BH3.THF. 相似文献
168.
A novel synthesis of tetralactosaminyl O-glycoamino acid is described. The stereoselective assemblage of a lactosaminyl unit was performed by 2-trichloroacetamido group-assisted β-glycosylation. Initial investigation into the synthesis of decasaccharyl threonine 2 showed limited success because of the low yield in the step concerning the removal of 4-O-chloroacetyl groups. In contrast, 4-O-benzylated decasaccharyl threonine 50 was efficiently synthesized from key LacNAc derivative 35 carrying a 3-O-allyl protecting group at the Gal residue by reiterative glycosylation using the (N-phenyl)trifluoroacetimidate method. Decasaccharide 50 was used as a building block in the solid-phase synthesis of a MUC1-related glycopeptide. Synthetic glycopeptide was obtained through two acidic processes: cleavage from resin with reagent K at a lowered temperature and debenzylation with a diluted cocktail of low-acidity TfOH. Desired glycopeptide 54 was isolated as the major product, while a series of the saccharide-shortened minor products were generated due to the acid-labile property of the β-GlcNAc glycosidic linkages. 相似文献
169.
Sei-ichiro Ueki 《Complex Analysis and Operator Theory》2012,6(3):549-560
We will investigate the order boundedness of weighted composition operators ${uC_{\varphi}}$ from weighted Bergman spaces ${L_{a}^p(dA_{\alpha})}$ , weighted-type spaces ${H_{\alpha}^{\infty}}$ or Bloch-type spaces ${\mathcal{B}_{\alpha}}$ into the space ${L_{a}^q(dA_{\beta})}$ . 相似文献
170.