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21.
Takanori Suzuki Tomohiro Iwai Eisuke Ohta Hidetoshi Kawai Kenshu Fujiwara 《Tetrahedron letters》2007,48(20):3599-3603
Huge CD amplitude (A = +538) was attained by diastereomeric preference (50% de) for the title dication with two bis[4-(R)-sec-butoxyphenyl]methylium units in benzene at 23 °C. Intramolecular π-π stacking is the origin for effective transmission of point chirality to axial chirality to attain the chiroptical enhancement of 400-times. Thanks to the strong CD signaling, chiroptical changes upon electrolysis could be readily detected, thus realizing a new class of electrochiroptical response systems. Chiroptical properties could also be modified by solvent polarity. 相似文献
22.
Kiitiro Utimoto Yukio Wakabayashi Yuho Shishiyama Masaharu Inoue Hitosi Nozaki 《Tetrahedron letters》1981,22(43):4279-4280
Title transformation is accomplished by the catalytic action of SnCl2 or BF3·OEt2 Lithio derivative of 2,2-dimethoxyacetonitrile is used as synthetic equivalent of methyl lithioformate. 相似文献
23.
Takanori Suzuki Prof. Shoko Tanaka Hidetoshi Kawai Dr. Kenshu Fujiwara Prof. 《化学:亚洲杂志》2007,2(1):171-177
The title heterocyclic donors undergo reversible C? C bond formation/cleavage upon electron transfer (dynamic redox behavior). The helical sense in both neutral and cationic states is interconvertible by facile ring flipping. The π‐type asymmetric center on the azepine nitrogen atom induces a significant degree of diasteromeric preference, thus endowing strong CD activity based on exciton coupling. Chiroptical properties could be modified not only by redox reactions but also by heat and protonation. The present redox pairs can serve as unprecedented three‐way‐input (e, H+, Δ) and two‐way‐output (UV/Vis, CD) response systems. 相似文献
24.
25.
S Yokohama T Miwa S Aibara H Fujiwara H Matsumoto K Nakayama T Iwamoto M Mori R Moroi W Tsukada 《Chemical & pharmaceutical bulletin》1992,40(9):2391-2398
A series of 6-alkyl- or 6-(cycloalkylalkyl)-[1,3,4]thiadiazolo[3,2- a]-1,2,3-triazolo[4,5-d]pyrimidin-9(3H)-ones 1b--o was synthesized from the corresponding 1,3,4-thiadiazol-5-amines 3b--o and the antiallergic activities of the products were evaluated. Among the compounds 6-(2-cyclohexylethyl)- [1,3,4]thiadiazolo[3,2-a]-1,2,3-triazolo[4,5-d]pyrimidin-9(3H)-one 1h, whose X-ray crystallographic stereostructure is shown, was found to be a promising new antiallergic agent, which has low toxicity and dual activity as a leukotriene D4 receptor antagonist and as an orally active mast cell stabilizer. 相似文献
26.
2,3,7,8-Substituted polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and non-ortho-substituted polychlorinated biphenyls (PCBs) account for almost all of the total toxic equivalents (TEQ) in environmental samples. Activated carbon columns are used to fractionate the samples for GC-MS analysis or bioassay. Micropore-free surface-activated carbon is highly selective for PCDD/Fs and non-ortho-PCBs and can improve the conventional activated carbon column clean-up. Along with sulfuric acid-coated diatomaceous earth columns, micropore-free surface-activated carbon provides a rapid, robust, and high-throughput sample preparation method for PCDD/Fs and non-ortho-PCBs analysis. 相似文献
27.
Yukio Shimura Noboru Ikeda 《Journal of polymer science. Part A, Polymer chemistry》1973,11(6):1271-1280
Bis-ε-aminocaproylaminocaproylhexamethylenediamine ( I ) was synthesized as an analog of 6-nylon pentamer diamine, and its incorporation into block copolymers was studied with the use of α,ω-dihydroxyl, α,ω-bisdimethylchlorosilyl, and α,ω-diepoxy polystyrene. In the course of the experiments, the stability and the reactivity of 4,4′-diphenylmethane diisocyanate and tetramethylene diisocyanate in aprotic dipolar solvents were examined by infrared spectroscopy. The only usable solvent, N-methylpyrrolidone, was found still inadequate for the synthesis involving I, diisocyanate, and α,ω-dihydroxyl polystyrene. A block copolymer having M n = 18,000 was obtained by the reaction of I and α,ω-diepoxy polystyrene. All Tg values of the block copolymers were above 90°C, higher than for polystyrenes with corresponding molecular weight. 相似文献
28.
Factors affecting the storage stability of lyophilized cationic liposomes were investigated using liposomes prepared with various excipients and by different freezing rates, either quick freezing (freezing by immersion into liquid nitrogen) or slow freezing (cooling to -50 degrees C at a rate of -10 degrees C/h). Increases in the particle size of cationic liposomes observed during freeze-drying were inhibited by the addition of sucrose, trehalose and sucrose-dextran mixtures (1 : 1 and 2 : 1 by weight). The storage instability of the formulations, as indicated by changes in particle size, was affected by their glass transition temperature (T(g)). Addition of high-T(g) excipients resulted in smaller increases in the particle size, indicating improvement of storage stability. The storage stability of cationic liposome formulations was also affected by freezing rate. Formulations prepared by slow freezing exhibited better stability. Longer shear relaxation times were observed for formulations prepared by slow freezing compared with those prepared by quick freezing. This indicates that formulations prepared by slow freezing have a lower matrix mobility, which may result in better storage stability. T(g) or (1)H-NMR relaxation measurements could not detect differences in matrix mobility between formulations prepared by different freezing rates. Shear relaxation measurements seem to be a useful method for evaluating the storage stability of cationic liposome formulations. 相似文献
29.
Radical iodine atom transfer [3 + 2] cycloaddition with various alkenes using dimethyl 2-(iodomethyl)cyclopropane-1,1-dicarboxylate and 1,1-bis(phenylsulfonyl)-2-(iodomethyl)cyclopropane as new precursors of a homoallyl radical species smoothly proceeds to give functionalized cyclopentane derivatives in good yields. 相似文献
30.
Masahiro Irie Senzo Sasaoka Yukio Yamamoto Koichiro Hayashi 《Journal of polymer science. Part A, Polymer chemistry》1979,17(3):815-820
Photopolymerization of cyclohexene oxide in the presence of electron acceptors was studied in a bulk system (in liquid as well as in solid states). The polymerization was proved to proceed by a cationic mechanism in both states by the effect of inhibitors. In a liquid phase the light intensity dependence of the rate of polymerization and the molecular weight distribution showed a contribution of a free ionic polymerization. Any discontinuous phenomenon in the rate as well as in the molecular weight was not discerned between liquid(above ?36°C) and plastic crystal (between ?36 and ?81°C) phases. A quantum yield of monomer consumption as high as 8 × 103 was observed in the plastic crystal phase. Below ?81°C in the normal crystal phase the rate as well as the molecular weight was remarkably suppressed. 相似文献