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71.
Atsushi Sudo Tomoki Yamasaki Takuro Yamashita Dai Ishida 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):2407-2414
Oligo(spiroketal)s (OSKs) were synthesized from myo‐inositol, a naturally occurring cyclic compound bearing six hydroxyl groups. The successful synthesis of OSKs was achieved using silyl ethers 2 derived from 1,4‐di‐O‐alkylated myo‐inositol 1 as monomers, which underwent polycondensation with 1,4‐cyclohexanedione (CHD) at 0 °C in the presence of trimethylsilyl triflate as a catalyst. Because of the irreversible nature of the condensation reaction of silyl ethers with ketones, the resulting OSKs 7 had higher molecular weights than previously reported OSKs that were obtained by polycondensation of tetraols 1 with CHD, where backward hydrolysis of the ketal functions occurred. In addition, another series of OSKs, 8, were synthesized using silyl ethers 3 derived from 2,5‐di‐O‐alkylated myo‐inositol 6 , which are more symmetric monomers than silyl ethers 2 . Silyl ethers 3 underwent efficient polycondensation with CHD, whereas tetraol 6 did not, demonstrating that the derivation of such tetraols into the corresponding silyl ethers is a powerful strategy to access OSKs. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2407–2414 相似文献
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Toni Neuwirth Dr. Anne-Catrin Letzel Cedric Tank Dr. Keishi Ishida Michael Cyrulies Dr. Lisa Schmölz Prof. Dr. Stefan Lorkowski Prof. Dr. Christian Hertweck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15855-15858
The anaerobe Clostridium acetobutylicum belongs to the most important industrially used bacteria. Whereas genome mining points to a high potential for secondary metabolism in C. acetobutylicum, the functions of most biosynthetic gene clusters are cryptic. We report that the addition of supra-physiological concentrations of cysteine triggered the formation of a novel natural product, clostrisulfone ( 1 ). Its structure was fully elucidated by NMR, MS and the chemical synthesis of a reference compound. Clostrisulfone is the first reported natural product with a diphenylsulfone scaffold. A biomimetic synthesis suggests that pentamethylchromanol-derived radicals capture sulfur dioxide to form 1 . In a cell-based assay using murine macrophages a biphasic and dose-dependent regulation of the LPS-induced release of nitric oxide was observed in the presence of 1 . 相似文献
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Ishibashi Chiaki Ichiyama Mai Ishida Naoya Kitamura Naoto Idemoto Yasushi 《Journal of Solid State Electrochemistry》2022,26(3):663-682
Journal of Solid State Electrochemistry - The stable structures associated with the second charge of MgCo2−xMnxO4 (x = 0, 0.5), where Mg is removed from the stable first-discharge... 相似文献
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Reductive dehalogenation of aryl halides was achieved using hydrogen and a palladium catalyst. By using deuterium gas, the deuterated arenes were readily prepared. 相似文献
79.
Xiaoxue Ye Satomi Mori Zhongqi Xu Shinjiro Hayakawa Takeshi Hirokawa 《Electrophoresis》2013,34(22-23):3155-3162
The phenomenon of peak area decrease due to high injection voltage (Vinj, e.g. 10–30 kV, 200–600 V/cm in the 50 cm capillary) was found in the analysis of very dilute DNA fragments (<0.2 mg/L) by using high‐sensitive electrokinetic supercharging‐CGE. The possibility of DNA cleavage in aqueous solution was suggested, in addition to the aggregation phenomenon that is already known. The analysis of intentionally voltage‐affected fragments (at 200 V/cm) also showed decreased peak areas depending on the time of the voltage being applied. Computer simulation suggested that a high electric field (a few kV/cm or more) could be generated partly between the electrode and the capillary end during electrokinetic injection (EKI) process. After thorough experimental verification, it was found that the factors affecting the damage during EKI were the magnitude of electric field, the distance between tips of electrode and capillary (De/c), sample concentration and traveling time during EKI in sample vials. Furthermore, these factors are correlating with each other. A low conductivity of diluted sample would cause a high electric field (over a few hundred volts per centimeter), while the longer De/c results in a longer traveling time during EKI, which may cause a larger degree of damage (aggregation and cleavage) on the DNA fragments. As an important practical implication of this study, when the dilute DNA fragments (sub mg/L) are to be analyzed by CGE using EKI, injection voltage should be kept as low as possible. 相似文献
80.
Excited state intramolecular hydrogen atom transfer of phenylethynyl-substituted 2′-hydroxychalcones
Satomi Tasaki Atsuya Momotake Yoko Kanna Tatsuo Arai 《Research on Chemical Intermediates》2013,39(1):61-72
(E)-1-[2-Hydroxy-4-(phenylethynyl)phenyl]-3-[4-(phenylethynyl)phenyl]prop-2-en-1-one (1), (E)-1-[2-hydroxy-4-(phenylethynyl)phenyl]-3-phenylprop-2-en-1-one (2), and (E)-1-(2-hydroxyphenyl)-3-[4-(phenylethynyl)phenyl]prop-2-en-1-one (3), which belong to a new class of 2′-hydroxychalcones with phenylethynyl group(s) at the para position of the phenyl ring, were synthesized, and their photochemical properties were investigated. The lowest energy absorption band of 1 peaks at a longer wavelength (383 nm) with a much larger molar extinction coefficient (5.0 × 104 M ?1 cm?1) than that of the parent 2′-hydroxychalcone (2′HC) (2.0 × 104 M ?1 cm?1 at 318 nm). Upon photoexcitation, all three compounds underwent excited-state intramolecular hydrogen atom transfer (ESIHT) to produce an excited tautomer that emitted fluorescence with a large Stokes shift in the longer wavelength region at 600–700 nm. The quantum yield of the tautomer fluorescence of 1 was not high at 298 K (Φ f = 9.1 × 10?5), but was highest among 2′HC and its analogues. The Φ f values of 1–3 increased 10–30 fold upon reducing the temperature from 298 to 77 K. 相似文献