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371.
Ushida N Kondo T Tasaka S Park IG Song JS Hara T Homma Y Tsuzuki Y Fujioka G Fukushima H Takahashi Y Tatsumi S Yokoyama C Fujiwara K Taruma K Bahk SY Kim CO Park JN Bailey DC Conetti S Mercure P Trischuk J Turcotte M Aoki S Chiba K Fuchi H Hoshino K Kodama K Matsui R Miyanishi M Nakamura M Nakazawa K Niu K Niwa K Ohashi M Sasaki H Tomita Y Torii N Yamakawa O Yanagisawa Y Aubrecht GJ Dunlea J Errede S Gauthier A Gutzwiller MJ Kuramata S Oleynik G Reay NW Reibel K Sidwell RA Stanton NR Moriyama K 《Physical review letters》1986,56(17):1771-1774
372.
Y Takeuchi M R Chang K Hashigaki T Tashiro T Tsuruo S Tsukagoshi M Yamato 《Chemical & pharmaceutical bulletin》1992,40(6):1481-1485
Novel indolo[3,2-b]quinolines (1b-k), having a nitro, amino, acetamido, methanesulfonamido, or glycosylamino group at the 2, 7, or 8-position, were prepared and their antitumor activities against P388 leukemia in mice were examined. The 7-galactopyranosylamino derivative (1g) showed the most potent activity (optimal dose = 25 mg/kg, T/C greater than 333%, cure rate 5/6). 相似文献
373.
Octakis(2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl)-gamma-cyclodextrin (2,3-MOM-6-TBDMS-gamma-CD) was employed as stationary phase for capillary gas chromatographic separation of enantiomers. Selective introduction of the acetal function at positions 2 and 3 of the glucose units was achieved by reaction of 6-O-TBDMS-gamma-cyclodextrin with methoxymethyl chloride. 2,3-MOM-6-TBDMS-gamma-CD was shown to be a chiral stationary phase suitable for enantiodifferentiation of a broad spectrum of chiral volatiles from various chemical classes. A total of 125 pairs of enantiomers could be separated. Structural influences of the analytes on the enantioseparation were demonstrated. High alpha values up to 1.8 were observed for the hydroxyketone acetoin and some methyl branched ketones. Pronounced enantioseparations were also determined for cyclic pentenolone and furanone derivatives. 相似文献
374.
Takehiko Yamato Koji Fujita Naoki Shinoda Kozo Noda Yoshiaki Nagano Takashi Arimura Masashi Tashiro 《Research on Chemical Intermediates》1996,22(9):871-897
The hydrolysis of 8-bromomethyl[2.2]metacyclophanes 3 to the corresponding 8-hydroxymethyl derivatives 4 was carried out in 83% aqueous dioxane solution at 25°C. Substituent effect through space on the rate of the hydrolysis of bromomethyl groups attached on the opposite aromatic ring was first found in this investigation. Interestingly, the introduction of the substituents at the internal position 16 tends to enhance the hydrolysis reaction rate 10–100 times. It was found also that the stabilization by both the direct through-space cation-π-interaction and the interaction through the intra-annular 8,16-position are possible in the [2.2]metacyclophane 8-benzyl cations. The good correlation with log(K/KH) and σp + was observed for the hydrolysis of internally unsubstituted 5-bromomethyl[2.2]MCPs 7, in which the direct through-space cation-π-interactions are not possible. TiCl4 and Nafion-H, a perfluorinated resinsulfonic acid, catalysed Friedel-Crafts benzylation of benzene and substituted benzenes with 8-bromomethyl- and 8-hydroxymethyl[2.2]metacyclophanes to afford 8-benzyl[2.2]metacyclophanes is described. A high substrate and positional selectivity were observed in the present benzylation reaction quite different from those obtained from the benzyl bromide and benzyl alcohol. The benzyl cation intermediate stabilized by the through-space electronic interaction among the opposite benzene ring was first demonstrated in the benzylation of [2.2]metacyclophane systems. The mild and selective transannular reaction attributable to the highly strained character of [2.2]metacyclophane skeleton and the increased stabilization of the 5-benzyl cation intermediate arising from the electronic interactions among the opposite benzene ring through the intra-annular 8,16-positions was also observed. 相似文献
375.
Yoshimoto Abe Akira Kaijou Yukinori Nagao Takahisa Misono 《Journal of polymer science. Part A, Polymer chemistry》1988,26(2):419-427
In order to obtain polysiloxanes capable of forming a film, the preparation and properties of allyldimethylsilylated silicic acid was investigated. The reaction in variable molar ratios of allyldimethylchlorosilane to silicic acid gave partially silylated silicic acids with different degrees of silylation. They provided not only fibrous polysiloxanes but also films from concentrated polymer solutions. Spinnability and film formation depended on the solvent, degree of silylation, molecular weight, and allyl group. 相似文献
376.
[reaction: see text] An N-acyliminium ion pool was found to undergo cycloaddition reaction with a variety of dienophiles such as alkenes and alkynes. A concerted mechanism seems to be most likely for alkyl-substituted alkenes as suggested by the DFT calculations, whereas a stepwise mechanism plays the major role for aryl-substituted alkenes. It is also noteworthy that the present study demonstrates the potential of the combination of the cation pool method and the micromixing in both mechanistic and synthetic aspects. 相似文献
377.
Takahiro Gunji Yukinori Nagao Takahisa Misono Yoshimoto Abe 《Journal of polymer science. Part A, Polymer chemistry》1992,30(9):1779-1787
Silicic acid (SA) was extracted with THF from aqueous sodium metasilicate (SMS) solutions neutralized with hydrochloric acid, followed by silylation to give silylated SA from which the condensation and structure of SA in tetrahydrofuran (THF) were investigated. The degree of extraction markedly depends on SA and HCl concentrations. The condensation of 0.86 and 3.5 mol/L SA-THF solutions was followed by measuring the viscosity of the solutions at 0 and 20°C. The silylated SA was isolated as a distillate (LS) and a residue (HS) with low and high M?ns (ca. 1300 and 3800) by vacuum distillation. The ratio of LS against HS decreased as a SA concentration in THF increased. In an aqueous solution, SA exists as lower molecular weight SAs compared with those in THF. SAs such as monomer, dimer, cyclic tri- and tetramer were the main components in a 0.1 mol/L aqueous solution. On the extraction with THF from an aqueous solution, SA was found to undergo condensations to form more polymerized SAs. From the THF solutions of SA concentration above 0.5 mol/L, the HS was obtained as a main component (73%) which was expected to have ladder-like structures. © 1992 John Wiley & Sons, Inc. 相似文献
378.
M Yamato Y Takeuchi M R Chang K Hashigaki T Tsuruo T Tashiro S Tsukagoshi 《Chemical & pharmaceutical bulletin》1990,38(11):3048-3052
Some tetracyclic quinolines (9 and 14) with a [2-methoxy-4-[(methylsulfonyl)amino]phenyl]amino side chain were prepared and their deoxyribonucleic acid (DNA) intercalative properties, KB cytotoxicity, antitumor activity (P388 leukemia), and ability to induce topoisomerase II dependent DNA cleavage were investigated. The indoloquinoline derivative 9 exhibited the most potent activity (dose = 6.3 mg, T/C% = 300) in this series. The steric structural features of the chromophores of the compounds previously and newly synthesized were studied by a computer-associated molecular graphics technique. Relationships between the steric structural features of the chromophores and biological activities are also discussed. 相似文献
379.
N. Hayashi J. Ishida A. Yamato M. Iwai M. Kinoshita 《Journal of Radioanalytical and Nuclear Chemistry》1987,115(2):369-376
An accurate and reliable method has been developed and routinely carried out for the sequential determination of239,240Pu and241Am in environmental samples. After suitable pretreatment.239,240Pu and241Am are separated from other elements by means of the anion exchange resin method. Americium-241 is purified by coprecipitation with calcium oxalate and then ion exchanged in mixed media of the mineral acid-methanol. In the analysis,242Pu (or236Pu) and244Cm are used as chemical yield monitors. The recoveries of the yield monitors in the analyses of some kinds of environmental samples were 7080% for plutonium and 7686% for curium. The concentration of239,240Pu in the coastal sea water were 7.022 Bq/l and that of241Am was 1.26.3 Bq/l. The mean concentrations of239,240Pu in the edible parts of the marine products ranged from 0.22 to 7.4 mBq/kg · fresh and those of241Am ranged from 0.11 to 2.6 mBq/kg · fresh. 相似文献
380.
Takahiro Gunji Yukinori Nagao Takahisa Misono Yoshimoto Abe 《Journal of polymer science. Part A, Polymer chemistry》1991,29(7):941-947
Preparation and properties of polytitanosiloxanes (PTS) as a preceramic polymer for SiO2-TiO2 fibers were investigated. The PTS was prepared by the reaction of bis(2,4-pentanedionato) titanium diisopropoxide (PTP) with silicic acid (SA), extracted with tetrahydrofuran from an aqueous solution, in methanol. They were soluble in methanol, ethanol, and THF. The molecular weight (Mn ) was 1500–4200 depending on the reaction molar ratio (SA/PTP). A Concentrated methanol solution of PTS showed an appreciable stability to self-condensation and good spinnability. Dry spinning of the solution provided golden yellow precursor fibers which can be subjected to thermal-treatment to give ceramic fibers. The PTS is considered to be a copolymer formed by the condensation of oligomeric silicic acid with PTP consisting of Si? O? Ti and Si? O? Si linkages in the molecular main chain with the ligand and hydroxy groups as pendants. 相似文献