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排序方式: 共有86条查询结果,搜索用时 15 毫秒
1.
Kento Nishikibe Keisuke Nishikawa Momochika Kumagai Matsumi Doe Yoshiki Morimoto 《化学:亚洲杂志》2022,17(1):e202101137
There are marine cytotoxic bromotriterpenoids, named the thyrsiferol family that are structurally characterized by some tetrahydropyran (THP) and tetrahydrofuran (THF) rings. The thyrsiferol family belongs to natural products that are often difficult to determine their stereostructures even by the current, highly advanced spectroscopic methods, especially in acyclic systems including stereogenic tetrasubstituted carbon centers. In such cases, it is effective to predict and synthesize the possible stereostructures. Herein, to elucidate ambiguous stereostructures and unassigned absolute configurations of aplysiol B, laurenmariannol, and saiyacenol A, members of the thyrsiferol family, we carried out their asymmetric chemical syntheses featuring 6-exo and 5-exo oxacyclizations of epoxy alcohol precursors and 6-endo bromoetherification of a bishomoallylic alcohol. In this paper, we report total assignments of their stereostructures through their asymmetric chemical syntheses and also their preliminary cytotoxic activities against some tumor cells. These results could not have been achieved without depending on asymmetric total synthesis. 相似文献
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Pankaj Sehgal Manu Sharma Kim Lambertsen Larsen Reinhard Wimmer Hidekazu Doe Daniel E. Otzen 《Journal of Dispersion Science and Technology》2013,34(6):885-890
Interactions of γ-cyclodextrin (γ-CD) with the single and mixed micelles of sodium dodecyl sulfate (SDS) and sodium lauroyl sarcosine (SLAS) have been studied at different concentrations of γ-CD by using conductivity measurements. From conductivity data, the pure and mixed critical micellar concentration (cmc), the equivalent ionic conductivities of the monomeric species (Λ m), the associated species (Λ assc) and the micelle (Λ mic), the degree of counterion dissociation (χ) in the presence of γ-CD have been evaluated from the slope of the conductivity versus concentration plots for the pure and binary mixture of surfactants. From the dependence of cmc of the surfactantson γ-CD concentration, we have deduced the association constant (K) of surfactant-γ-CD inclusion complexes assuming 2:1 stoichiometry. Theories of Clint, regular solution, and Motomura's have been used for the evaluation of ideality or nonideality of the mixed system. Mixed micelles were found to be rich in SDS content in the presence and the absence of γ-CD. The cmc values have been used to evaluate the transfer of standard free energy of micelles (ΔG0 M,tr) from the aqueous medium to additive medium. 相似文献
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Pankaj Sehgal Manu Sharma Kim Lambertsen Larsen Reinhard Wimmer Daniel E. Otzen Hidekazu Doe 《Journal of Dispersion Science and Technology》2013,34(1):128-133
In this work, we have studied the influence of different concentrations of β‐Cyclodextrin (β‐CD) on the mixed micellization of anionic surfactants sodium dodecyl sulfate (SDS) and sodium lauroyl sarcosine (SLAS) at different SDS mole fractions (αSDS). From conductivity data, the critical micellar concentration (cmc), the equivalent ionic conductivities of the monomeric species (Λm), the associated species (Λassc) and the micelle (Λmic), the degree of counterion dissociation (α) in the presence of β‐CD were evaluated from the slope of the conductivity versus concentration plots for the pure and binary mixtures. The apparent cmc of the surfactants vary linearly with the β‐CD concentrations. From the dependence of cmc of the surfactants on β‐CD concentration, we have deduced the association constant (K) of surfactant‐β‐CD inclusion complexes assuming 1∶1 stoichiometry. Theories of Clint, Regular solution, and Motomura's have been used for the evaluation of ideality or nonideality of the mixed system. Mixed micelles were found to be rich in SDS content at the cmc in the presence and the absence of β‐CD. The cmc values have been used to evaluate the transfer of standard free energy of micelles (ΔG0 M,tr) from the aqueous medium to additive medium. 相似文献
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Toshihiko Ueki Matsumi Doe Yoshiki Morimoto Takamasa Kinoshita Rika Tanaka Kazuo Yoshihara 《Journal of heterocyclic chemistry》2001,38(1):165-172
Hyperolactones A ( 1 ) and C ( 3 ) have been synthesized starting from (S)‐malic acid by a straightforward route. The unique spirolactone skeleton was efficiently constructed by one‐pot reaction as a key step. The absolute stereochemistry of hyperolactones was unambiguously established by this synthesis. 相似文献
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Photodissociation processes of H2O2 in the range 193–240 nm have been studied by pulsed laser photolysis and laser‐induced fluorescence detection of H atom fragments at 121.56 nm. The quantum yield values for H atom formation at 295 ± 2 K have been determined to be 0.20 ± 0.03, 0.038 ± 0.008, 0.029 ± 0.003, 0.015 ± 0.006, 0.007 ± 0.002 at 193, 207, 210, 220, and 230 nm, respectively. At 240 nm, only the upper limit value of <0.002 has been obtained. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 751–754, 2005 相似文献
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Kinichi Obi Yutaka Matsumi Yasuaki Takeda Shinya Mayama Hajime Watanabe Soji Tsuchiya 《Chemical physics letters》1983,95(6):520-524
The new nozzle assembly using Hg-photosensitized reaction has been developed to obtained a jet-cooled radical beam. This technique was applied to produce a HNO radical beam. Laser-induced flourescence excitation spectra were obtained for the 1A″ — 1A′ system. Time-resolved measurements yielded fluorescence lifetimes of 22–29 μs for single rovibronic levels of HNO. 相似文献