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901.
The polymerization of alkyl vinyl ethers initiated by hydrogen iodide and iodine catalyst has been studied in detail. The polymerization showed living behavior in nonpolar solvents at low (-15°) temperatures as reported earlier by others. The observed rate of polymerization under the reaction conditions was linearly dependent on the initial concentration of hydrogen iodide and iodine, respectively. However, the monomer concentration did not influence the rate of polymerization (apparent zero order). From the observed rate equation, two possible reaction schemes were proposed and attempts were made to distinguish them by using UV/visible spectroscopy and 13 C-NMR spectroscopy. In both schemes a reversible interaction between monomer and an iodine molecule was postulated as a necessary elemental reaction to fit the observed expression for rate of polymerization. From the spectroscopic analysis results, the interaction between the iodide compound (chain end) and the iodine molecule seems to be very weak compared to the interaction between monomer and the iodine molecule. 相似文献
902.
Tae Wan Lee Dae Hee Lee Jicheol Shin Min Ju Cho Dong Hoon Choi 《Journal of polymer science. Part A, Polymer chemistry》2013,51(24):5280-5290
Novel naphtho[1,2‐b:5,6‐b′]dithiophene (NDT) and diketopyrrolopyrrole (DPP)‐containing donor‐acceptor conjugated polymers (PNDTDPPs) with different branched side chains were synthesized via Pd(0)‐catalyzed Stille coupling reaction. Octyldodecyl (OD) and dodecylhexadecyl (DH) groups were tethered to the DPP units as the side chains. The soluble fraction of PNDTDPP‐OD polymer in chloroform has much lower molecular weight than that of PNDTDPP‐DH polymer. PNDTDPP‐DH polymer bearing relatively longer DH side chains exhibited much better charge‐transport behavior than PNDTDPP‐OD polymer with shorter OD side chains. The thermally annealed PNDTDPP‐DH polymer thin films exhibited an outstanding charge carrier mobility of ~1.32 cm2 V?1 s?1 (Ion/Ioff ~ 108) measured under ambient conditions, which is almost six times higher than that of thermally annealed PNDTDPP‐OD polymer thin films. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5280–5290 相似文献
903.
A series of new 1, 2-O-isopropylidene-3-O-methyl-6-deoxy-6-N, N-dialkylamino-α-D-glucofuranoses 1 and 1, 2-O-isopropylidene-3, 6-dideoxy-6-N, N-dialkylamino-α-D-glucofuranoses 1′ were prepared from α-D-glucose and their enantiose-lectivities compared as chiral catalysts for the ethylation of benzaldehyde and heptanal with diethylzinc. 相似文献
904.
Synthesis of a Tricyclic Bisguanidine Compound Structurally Related to Saxitoxin and its Identification in Paralytic Shellfish Toxin‐Producing Microorganisms
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Shigeki Tsuchiya Dr. Yuko Cho Prof. Dr. Keiichi Konoki Prof. Dr. Kazuo Nagasawa Prof. Dr. Yasukatsu Oshima Prof. Dr. Mari Yotsu‐Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(21):7835-7840
We recently reported the chemical synthesis and identification of the genetically predicted biosynthetic intermediates of saxitoxin (STX), including a 2‐aminoimidazole‐bearing monoguanidine compound (Int‐C′2) in two paralytic shellfish toxin (PST)‐producing microorganisms. In this study, we achieved the direct conversion of Int‐C′2 into a tricyclic bisguanidine compound (called Cyclic‐C′), which is structurally related to STX, through oxidative intramolecular guanidine transfer to 2‐aminoimidazole catalyzed by Pd/C under basic conditions in air. By using HPLC‐MS analysis, Cyclic‐C′ was also identified in the PST‐producing microorganisms, suggesting that Cyclic‐C′ is either another biosynthetic intermediate or a shunt product of PSTs. In addition, a weak inhibitory activity of Cyclic‐C′ to the voltage‐gated sodium channels was detected by using a cell‐based assay. 相似文献
905.
Jimin Yoon Won Gun Kwack Wang-Seob Shim Jun Kyu Lee Dong Kee Jang Namyi Gu Ji-Yoon Cho Kyung-Tae Lee Eun Kyoung Chung 《Biomedical chromatography : BMC》2020,34(12):e4957
Cefpiramide is frequently used to treat biliary infections. However, no bioanalytical method has been validated to quantitate cefpiramide in human samples, particularly in bile. Therefore, this study was conducted to develop a simple, selective and validated high-performance liquid chromatographic method to determine cefpiramide in human plasma and bile. A protein precipitation procedure was used to extract cefpiramide and cefoperazone (internal standard, IS) from 200 μl of plasma and bile. Utilizing a Capcell Pak C18 column (4.6 × 250 mm), cefpiramide and IS were separated using the timed-gradient mobile phase consisting of 0.1 m sodium acetate (pH 5.2) and acetonitrile at a flow rate of 1 ml/min with photodiode array detector (wavelength set at 273 nm). The calibration curves showed linearity at concentrations ranging from 1 to 150 μg/ml in both plasma and bile (r2 > 0.999). The within- and between-run coefficients of variation (CVs) for plasma samples were 0.570–4.43 and 1.10–2.76%, respectively; for bile samples, the within- and between-day precision (CV) was 0.814–6.34 and 2.05–4.00%, respectively. Our newly developed bioanalytical method was successfully employed to quantify cefpiramide concentrations in both plasma and bile at multiple time points in patients with acute cholangitis. 相似文献
906.
907.
908.
Jae-Won Lee Do-Yoon Lee Young-Soon Lee Joo-Young Yoon Sang-Chae Jeon Ju-Ho Lee Seok-Min Hong Yung-Zun Cho 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(1):15-23
The electrolytic reduction process in pyroprocessing of used fuel requires that fuel fragments be pre-treated to remove cesium and iodine. The effect of high temperatures and fuel fragment size on release of cesium was investigated over 10 h at a temperature of 1300–1400 °C for fuel fragments with an O/U ratio of 2.2. Re-fragmentation of the original fragments was observed as changes in cesium release count rates as fuel was heated from 484 to 1329 °C. The release of cesium is highly dependent on the size of fuel fragments and most of the cesium is released as the temperature is held at the maximum target value. 相似文献
909.
910.
Young Jin Cho Seung Hwan Lee Jong Woo Bae Sung Hoon Kim Sam Rok Keum Cheol Min Yoon 《合成通讯》2013,43(12):2205-2211
The 7-acetoxyspiropyrans (4a and 4b) have been prepared by the reaction of Fischer's bases (3) with 2,4-diacetoxybenzaldehyde in refluxing ethanol in moderate yields. The acetyl group of 7-acetoxy-spiropyran 4a was easily removed to give a 7-hydroxyspiropyran 6 in high yield under the basic condition. 相似文献