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991.
Motozaki T Sawamura K Suzuki A Yoshida K Ueki T Ohara A Munakata R Takao K Tadano K 《Organic letters》2005,7(11):2261-2264
[reaction: see text]. Starting from diethyl (R)-malate, synthesis of the lower-half segment of (+)-tubelactomicin A, a 16-membered macrolide antibiotic, has been achieved. The synthesis involved the highly endo- and pi-facial selective intramolecular Diels-Alder reaction achieved using a trisubstituted methacrolein derivative tethering a 10-carbon dienyne unit at the beta-carbon, which in turn was prepared from a known allylated malic acid derivative. 相似文献
992.
Hiromitsu Kozuka Shinsuke Takenaka Hiroshi Tokita Toshihiro Hirano Yugo Higashi Takao Hamatani 《Journal of Sol-Gel Science and Technology》2003,26(1-3):681-686
Residual stress was evaluated by measuring the substrate curvature for alkoxide-derived silica and titania films deposited on silica glass substrates. The residual stress was tensile, increasing with increasing heat-treatment temperature. The stress in fired films was affected greatly by water/alkoxide ratio and chelating agents in starting solutions. Secondly, in situ observation was made on cracking of gel films subjected to heat-treatment. Silica and titania gel films deposited on silicon wafers were cracked in the heating-up stage at temperatures of 100°–400°C, depending on the film thickness and heating rate. Larger thickness and lower heating rates were found to lower the cracking onset temperature. Finally, organic polymers with amide groups were demonstrated to increase the uncracking critical thickness. The polymers include polyvinylpyrrolidone and polyvinylacetamide, allowing single layer ceramic coating films over 1 m in thickness to be formed without cracking. 相似文献
993.
Sakuda S Sugiyama Y Zhou ZY Takao H Ikeda H Kakinuma K Yamada Y Nagasawa H 《The Journal of organic chemistry》2001,66(10):3356-3361
Allosamizoline (1) is an aminocyclitol component of allosamidin, a Streptomyces metabolite, and has a cyclopentane ring originated from D-glucosamine. Biosynthesis of the cyclopentane ring was studied by feeding experiments with a variety of deuterium-labeled glucosamine and glucose. In the feeding experiments with [3-(2)H]- and [4-(2)H]-D-glucosamine and [1-(2)H]-D-glucose, deuterium was incorporated into C-3, C-4, and C-1 of 1, respectively. On the other hand, feeding experiments with [5-(2)H]- and [6,6-(2)H(2)]-D-glucosamine showed that deuterium on C-5 and one of the two deuterium atoms on C-6 of glucosamine were lost during the cyclopentane ring formation of 1. In the feeding experiments with (6R)- and (6S)-[6-(2)H(1)]-D-glucose, the (6R)-deuterium of glucose was incorporated into the proS position on C-6 of 1, but the (6S)-deuterium of glucose was not incorporated into 1. These results suggested that an intermediate with a 6-aldehyde group is involved in the biosynthesis of the cyclopentane ring moiety of 1 and overall inversion of stereochemistry of the C-6 methylene group occurred by stereospecific oxidation and reduction on C-6 during the formation of 1. The 6-aldehyde intermediate may play a key role in the biosynthetic step(s) of cyclization to form the cyclopentane ring and/or deoxygenation at C-5. 相似文献
994.
Hiroki Sakaguchi Keisuke Hatakeyama Mikio Fujii Hiroshi Inoue Chiaki Iwakura Takao Esaka 《Research on Chemical Intermediates》2006,32(5):473-481
ZrO2·1.5H2O or ZrO2·1.5H2O-KOH composite was used as an electrolyte in order to develop a solid-state nickel-metal hydride battery. The battery using
the ZrO2·1.5H2O-KOH composite had rechargeability, but had a very low discharge efficiency, even at low current density. However, the performance
of the battery was prominently improved by enlarging the electrode-electrolyte interface area. The resultant battery exhibited
the remarkably longer cycle life, the higher discharge efficiency, and the lower polarization: it was able to operate over
150 cycles at 10 mA/g alloy. 相似文献
995.
[reaction: see text] A practical method for the synthesis of optically active styrene oxides has been developed via formation of optically active 2-chloro-1-phenylethanols generated by reductive transformation of ring-substituted 2-chloroacetophenones. The optically active alcohols with up to 98% ee are obtainable from the asymmetric reduction of acetophenones with an S/C = 1000-5000 with a formic acid triethylamine mixture containing a well-defined chiral Rh complex, CpRhCl[(R,R)-Tsdpen]. 相似文献
996.
The reaction of p-substituted benzyl halides ((Y)BnX; X = Cl, Br, and I; Y = p-substituent, OMe, t-Bu, Me, H, F, Cl, and NO(2)) and copper(I) complexes supported by a series of (2-pyridyl)alkylamine ligands has been investigated to shed light on the mechanism of copper(I) complex mediated carbon-halogen bond activation, including ligand effects on the redox reactivity of copper(I) complexes which are relevant to the chemistry. For both the tridentate ligand (Phe)L(Pym2) [N,N-bis(2-pyridylmethyl)-2-phenylethylamine] and tetradentate ligand TMPA [tris(2-pyridylmethyl)amine] complexes, the C-C coupling reaction of benzyl halides proceeded smoothly to give corresponding 1,2-diphenylethane derivatives and copper(II)-halide complex products. Kinetic analysis revealed that the reaction obeys second-order kinetics both on the copper complex and the substrate; rate = k[Cu](2)[(Y)BnX](2). A reaction mechanism involving a dinuclear copper(III)-halide organometallic intermediate is proposed, on the basis of the kinetic results, including observed electronic effects of p-substituents (Hammett plot) and the rate dependence on the BDE (bond dissociation energy) of the C-X bond, as well as the ligand effects. 相似文献
997.
Katsuya?WatanabeEmail author Takahito?Kawakami Koji?Baba Nobuyasu?Oshio Takao?Kimura 《Catalysis Surveys from Asia》2005,9(1):17-24
We studied on the function of the metal in the sulfated zirconia(SO42–/ZrO2) catalyst for the isomerization reaction of light paraffins. The addition of Pt to the SO42–/ZrO2 carrier could keep the high catalytic activity. The improvement in this isomerization activity is because Pt promotes removal of the coke precursor deposited on the catalyst surface. Though this catalytic function was observed in other transition metals, such as Pd, Ru, Ni, Rh and W, Pt exhibited the highest effect among them. It was further found that the Pd/SO42–/ZrO2–Al2O3 catalyst possessed a catalytic function for desulfurization of sulfur-containing light naphtha in addition to the skeletal isomerization. The sulfur tolerance of catalyst depended on the method of adding Pd, and the catalyst prepared by impregnation of the SO42–/ZrO2–Al2O3 with an aqueous solution of Pd exhibited the highest sulfur tolerance.Further, we investigated the improvement in sulfur tolerance of the Pt/SO42–/ZrO2–Al2O3 catalyst by impregnation of Pd. The results of EPMA analysis indicated that this catalyst was a hybrid-type one (Pt/SO42–/ZrO2–Pd/Al2O3) in which Pt/SO42–/ZrO2 particles and Pd/Al2O3 particles adjoined closely. This hybrid catalyst possessed a very high sulfur tolerance to the raw light naphtha that was obtained from the atmospheric distillation apparatus, although this light naphtha contained much sulfur. We assume that such a high sulfur tolerance in the hybrid catalyst is brought about by the isomerization function of Pt/SO42–/ZrO2 particles and the hydrodesulfurization function of Pd/Al2O3 particles. Besides, since the hybrid catalyst also provides high catalytic activity in the isomerization of HDS light naphtha, we suggest that the Pd/Al2O3 particles supply atomic hydrogen to the Pt/SO42–/ZrO2 particles by homolytic dissociation of gaseous hydrogen and also enhance the sulfur tolerance of Pt/SO42–/ZrO2 particles. Finally, we also propose the most suitable location of Pd and Pt in the metal-supported SO42–/ZrO2–Al2O3 catalyst. 相似文献
998.
Chyongjin Pac Takao Fukunaga Yoshikazu Go-An Toshiyuki Sakae Shozo Yanagida 《Journal of photochemistry and photobiology. A, Chemistry》1987,41(1)
We have attempted to explore mechanistic aspects of the photosensitized ring-cleavage reactions of cis-1,2-diphenylcyclobutane (1), cis-transoid-cis-cyclobutal[1,2-a:4,3-a′] diindene (2) and r-1,c-2-dimethyl-t-3,t-4-di(4-methoxyphenyl)cyclobutane (3) by electron acceptors (A) in acetonitrile. The experimental results demonstrate that the ring cleavage of 1 and 2 occurs as a consequence of the rapid geminate recombination of ion-radical pairs occurring at a rate of well over 109 s−1 without ionic dissociation. In the case of 3, however, the photoreactions proceed by way of a chain-reaction mechanism involving the free cation radical of 3 which undergoes ring cleavage at much less than 107 s−1. The rapid ring cleavage of 1+ and 2+ is attributed to significant perturbations of the cyclobutane ring by the population of positive charge on the orbital array of the two π-electron systems and the cyclobutane-ring σ framework because of strong through-bond couplings. It is presumed that the cyclobutane ring of 3+ is much less distorted since the positive charge is mostly localized on the aryl group. The rapid geminate recombination of the A−−−1+ and A−−−2+ pairs is discussed in terms of a very efficient transition from the “distorted” and “ring-opened” minima of the A−−−D+ surface to the A–D surface. In the case of 3, this mechanism cannot be expected to operate in the geminate recombination. 相似文献
999.
Joachim Stckigt Karl-Heinz Pawelka Takao Tanahashi Bruno Danieli William E. Hull 《Helvetica chimica acta》1983,66(8):2525-2533
The structures of voafrine A and voafrine B, two novel dimeric indole alkaloids isolated from Voacanga africana Stapf cell suspension cultures, were established and the medium-dependent formation of both alkaloids was investigated. 相似文献
1000.
Houjou T Yamatani K Imagawa M Shimizu T Taguchi R 《Rapid communications in mass spectrometry : RCM》2005,19(5):654-666
Electrospray ionization mass spectrometry is used in lipidomics studies. The present research established a top-down liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) shotgun analysis method for phospholipids (PLs) using a normal-phase column or a C30 reverse-phase column with the data-dependent MS/MS scanning mode. A normal-phase column can separate most of the major different classes of PLs. By using LC/ESI-MS/MS with a normal-phase column, approximately 50 molecular species were identified in a PL mixture from rat liver. When the reverse-phase column was used, the PLs could be separated depending on their hydrophobicity, essentially the length of their fatty acyl chains and the number of unsaturated bonds in them. The LC/ESI-MS/MS method using a C30 reverse-phase column was applied to phosphatidylcholine (PC) and phosphatidylethanolamine (PE) mixtures as test samples. Molecular species with the same molecular mass but with different pairs of fatty acyl chains were separately identified. As a result, about 60 PC and 50 PE species were identified. PLs from rat liver were subjected to LC/ESI-MS/MS using the C30 reverse-phase column and about 110 molecular species were identified. Off-line two-dimensional LC/ESI-MS/MS with the normal-phase and C30 reverse-phase columns allowed more accurate identification of molecular species by using one-dimensional C30 reverse-phase LC/ESI-MS/MS analysis of the collected fractions. 相似文献