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61.
Syntheses of 3-substituted indazoles and benzoisoxazoles were efficiently accomplished with the aid of Pd-catalyzed intramolecular carbon-nitrogen and carbon-oxygen bond formations. The catalyst system described herein allows the cyclization to proceed under very mild conditions and thus could be applied to a wide range of substrates with acid- or base-sensitive functional groups. A total synthesis for the indazole ring-containing natural product nigellicine is also described. 相似文献
62.
63.
H. Takahashi N. Mri Y. Nagata S. Nakamura T. Uchida J. Akimitsu Y. Tokura 《Physica C: Superconductivity and its Applications》1993,210(3-4):485-488
The superconducting transition temperature (Tc) of Ba0.62K0.38Bio3 (Tc=30 K) has been measured under high pressure up to 8 GPa. It is observed that Tc increases initially with pressure, as reported by Uwe et al., Shirber et al. and Huang et al., but decreases above 4 GPa. The Hall coefficient of Ba0.62K0.38BiO3 has been measured up to 1.2 GPa. The absolute value of the Hall coefficient decreases with pressure by 10% GPa, the value of which is almost the same as that obtained in most CuO-based high-temperature superconductors. 相似文献
64.
Total cross sections for single-electron capture by He+ ions in vapor targets of Cs, Rb, K and Na have been determined in the energy range 0.4–5.0 keV. The energy dependence of the cross-section curves is very similar for all the targets. The cross sections for all the targets are maximum at about the same energy, 1.5 keV. Comparison is made with other reported experimental and theoretical results. 相似文献
65.
W. Nagata 《Tetrahedron》1961,13(4):278-286
Durch Einwirkung von 2 Mol Kaliumcyanid und 1·75 Mol Ammoniumchlorid und nachträgliche Ketalisierung und Acetylierung liess sich rac.
-Homo-18-nor-13(17a)-androstan-3β-ol-17-on (I) in die verschiedenen am C13 cyanierten Verbindungen verwandeln. Das Bildungsverhältnis von 13β- zur 13-Cyanverbindung lag bei 5:3. Die räumlichen Strukturen aller hierbei erhaltenen Verbindungen wurden ermittelt. Die angeführten Reaktionsfolgen stellen eine neue Methode zur Einführung der angularen Substituenten dar und lieferten einen Anhaltspunkt zur Totalsynthese der normalen sowie der in 18-Stellung mit einer funktionellen Gruppe versehenen Steroide. 相似文献
66.
Teruji Tsuji Takahiro Kataoka Mitsuru Yoshioka Yuji Sendo Yasuhiro Nishitani Shoichi Hirai Takashi Maeda Wataru Nagata 《Tetrahedron letters》1979,20(30):2793-2796
The benzyl ester protecting group in β-lactam derivatives can be cleanly removed by treatment with aluminum trichloride under mild conditions, preferably in the presence of anisole, to give the corresponding free acids in high yields. 相似文献
67.
Yoshio Hamashima Tadatoshi Kubota Koji Ishikura Wataru Nagata 《Tetrahedron letters》1979,20(51):4943-4946
7-Epi-1-oxacephem was obtained by stereospecific, intramolecular etherification of alcohol prepared from 7-epicephems via aldehyde or formate. Synthesis of the 3-acetoxymethyl analogwas unsuccessful. Biologically active 1-oxacephems were derived from by known processes. 相似文献
68.
Takao Yamazaki Masanori Nagata Katsuhide Matoba Hiroki Takahata Raymond N. Castle 《Journal of heterocyclic chemistry》1977,14(3):469-472
Homoveratrylamine (II) was condensed with 3-(2-carbomethoxyethyl)-1,3-dimethyl-2-pyrrol-idone (Ib) to furnish the corresponding amide (III), which was subjected to the Bischler-Napieralski reaction to afford the corresponding dihydroisoquinoline derivative (IV). Compound V was obtained by the reductive ring closure of Vila which was obtained by the hydrogena-tion of IV. The stereochemistry of V is proposed to have the anti-trans-trans quinolizidine conformation. 相似文献
69.
The interaction energy for base stacking in single-stranded poly A is calculated by an ab initio MO method. The calculated value agrees well with the observed stacking enthalpy. Dispersion and charge transfer interactions are the main factors stabilizing the polynucleotide; the contribution of the former is dominant. 相似文献
70.