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91.
Total synthesis of (±)-sesbanine () was carried out using γ-addition of ketene silyl acetal of methyl 3-cyclopentenecarboxylate to quaternized methyl nicotinate. The resulting 1,4-dihydropyridine () was oxidized with DDQ to give 4-substituted nicotinate () and was converted to alcohol () by stereoselective oxymercuration followed by treatment with ammonia to give . 相似文献
92.
Perret F Nishihara M Takeuchi T Futaki S Lazar AN Coleman AW Sakai N Matile S 《Journal of the American Chemical Society》2005,127(4):1114-1115
We report that the efflux of 5(6)-carboxyfluorescein anions from neutral egg yolk phosphatidylcholine vesicles is mediated by oligo/polyarginines only in the presence of activating amphiphilic anions. Screening of anion activators reveals best synergism for amphiphilic carboxylates (fullerene > calix[4]arene approximately coronene > pyrene > calix[6]arene > alkyl), whereas amphiphilic sulfates show less satisfactory activation despite often lower effective concentrations. The analogous alcohols and one calix[4]arene diphosphate were inactive. These results are discussed in the context of a tentative anion carrier mechanism, where interactions with bilayer (interface-directed translocation) and carrier (arene-templated carboxylate-guanidinium pairing) contribute to activator efficiencies. Applied to HeLa cells, pyrenebutyrate is shown to significantly increase the uptake of a fluorescently labeled octaarginine in a concentration-dependent manner. 相似文献
93.
Masayuki Nihei Takuya Nankawa Masato Kurihara Hiroshi Nishihara 《Angewandte Chemie (International ed. in English)》1999,38(8):1098-1100
Metal–metal bond formation by a cobaltadithiolene complex was observed for the first time in the reaction of [Co(η5-C5H5)(S2C6H4)] with [Mo(CO)3(py)3] and BF3 to give the Co-Mo-Co cluster 1 . Cyclic voltammetry reveals that 1 undergoes two one-electron reduction steps at the Co centers, which is indicative of transmission of the Co−Co electronic interaction through the Mo center. 相似文献
94.
Rubbery poly(organophosphazene)s were synthesized, and were combined with cobaltporphyrin (CoP) which binds molecular oxygen rapidly and reversibly. The apparent oxygen-binding equilibrium constant (Kapp) is in proportion to the physical solubility coefficient of oxygen in the polymer, although the reduced equilibrium and thermodynamic parameters are not dependent on the polymer matrix species. Diffusivity of oxygen via the fixed CoP(DC) is enhanced for poly(organophosphazene) membranes with a larger oxygen diffusion constant. Poly(organophosphazene) membranes with both a large Kapp and DC yield high oxygen permeability. 相似文献
95.
96.
Thin film growth of 6,13-pentacenequinone (C24H12O2, PnQ) on Si(1 1 1)-7 × 7 at room temperature (RT) was studied by low-energy electron microscopy (LEEM) and ab initio density functional theory (DFT) calculations. Our experiments yielded direct microscopic observation of enantiomorphic evolution mechanism in the initial stage of the chiral-like growth of PnQ islands, under kinetic growth conditions. We observed that the faster growth direction aligns with the direction of easier molecule incorporation, or lowest kink formation energy, rather than along the lowest energy step. Real time observation of the growth and subsequent relaxation of island shape revealed that kinetically stiff direction differs from the thermodynamic one. This feature together with anisotropic mass incorporation determines the enantiomorphic evolution and rotational arrangement of crystallites during the growth of elongated organic molecules, like PnQ. 相似文献
97.
Aiura Y Hase I Bando H Yagi-Watanabe K Ozawa K Iwase T Nishihara Y Shiino O Oshima M Kubota M Ono K 《Physical review letters》2003,91(25):256404
We present a detailed angle-resolved photoemission study on the layered transition-metal dichalcogenide 1T-TaS1.2Se0.8 in the commensurate charge-density-wave (CDW) phase. A drastic reduction in the spectral weight along the high symmetry line GammaM, particularly around the point M, is observed when s-polarized light was used. This implies that the initial state must be symmetric with respect to a mirror plane perpendicular to the line GammaK, which is consistent with conventional band calculations in the absence of the CDW. We conclude that there is only a limited amount of modification of the electronic structure of 1T-TaS1.2Se0.8 in the commensurate CDW phase due to the CDW-related potential. 相似文献
98.
A new "molecular photoelectronic transducer", working in a cyclic manner totally powered with light irradiation, has been constructed. The UV/blue-controlled repetitive motion of azobenzene moieties in 6,6'-bis(4' '-tolylazo)-4,4'-bis(4-tertbutylphenyl)-2,2'-bipyridine causes reciprocal CuI translocation between two coordination environments, resulting in pumping of the redox potential of CuI. Therefore, UV/blue light information can be successfully transformed into an electrode potential change and positive/negative current response, which is closely related to natural visual transduction both functionally and mechanically. This result demonstrates a new strategy for artificial molecular machine assembly, i.e. forming a path with multistep chemical reactions between input/output couples at choice. 相似文献
99.
[reaction: see text] Palladium-catalyzed cyanoesterification of norbornenes proceeds stereoselectively via NC-Pd-COOR (R = Me and Et) complexes as intermediates. 相似文献
100.
Nunokawa K Ito M Sunahara T Onaka S Ozeki T Chiba H Funahashi Y Masuda H Yonezawa T Nishihara H Nakamoto M Yamamoto M 《Dalton transactions (Cambridge, England : 2003)》2005,(16):2726-2730
New mixed metal clusters with M19 metal frameworks have been synthesized by NaBH4 reduction of Au(NO3)(PMe2Ph) together with AgNO3 in ethanol. Single crystal X-ray diffraction has revealed Au12Ag7 and Au17Ag2 metal skeletons for these clusters, which are best described in terms of bicapped pentagonal antiprismatic cages with a staggered-staggered M(5) ring configuration. These clusters connect the missing link between M13 icosahedral and M25 biicosahedral clusters providing a view of the cluster growth process. A TEM image of this cluster has been observed, which has clearly demonstrated single-sized nano-particles of less than 1.0 nm. 相似文献