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排序方式: 共有317条查询结果,搜索用时 93 毫秒
1.
Takanori Shiba 《Tetrahedron letters》2004,45(16):3211-3213
Rhodium-catalyzed carbonylation of 2-alkynylbenzylamines under water-gas shift reaction conditions gives a seven-membered heterocyclic product, 2,4-disubstituted-1,4-dihydrobenz[c]azepin-3-ones, in a good yield. 相似文献
2.
T Kusama T Soga Y Ono E Kumazawa E Shioya Y Osada S Kusumoto T Shiba 《Chemical & pharmaceutical bulletin》1991,39(8):1994-1999
Two novel analogs of a biosynthetic precursor of lipid A (2) were synthesized. The one analog (3) has acyl groups identical to those of 2, and the other (4) has tetradecanoyl groups in place of the (R)-3-hydroxytetradecanoyl groups of 2. Both 3 and 4 possess an alpha-glycosidically-bound phosphonooxyethyl group in place of the alpha-glycosyl phosphate group of 2. Compounds 3 and 4 exhibited definite antitumor activity against Meth A fibrosarcoma and low toxicity in rabbits, as the original compound 2 does. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups barely affected the antitumor activity, but slightly enhanced the toxicity in rabbits. 相似文献
3.
Fumie Takei Daisuke Kodama Sugiko Nakamura Kiyotaka Onitsuka Shigetoshi Takahashi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):585-595
Aryl isocyanides bearing free‐base and metallo‐porphyrins were prepared and polymerized with a Pd–Pt μ‐ethynediyl complex as the initiator to give polymers with narrow polydispersity indices. The molecular weights of the resulting polymers were precisely controlled by the initial feed ratio of the porphyrin monomer to the initiator. The UV–VIS spectra suggested that the porphyrin pendants are regularly arranged to form stacked columns. Metallo‐porphyrin polymers were also prepared by reacting free‐base porphyrin polymers with metal salts. The successive reactions of free‐base and zinc‐porphyrin monomers resulted in the formation of diblock polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 585–595, 2006 相似文献
4.
Katsuki Kusakabe Kiyotaka IchikiJun-ichiro Hayashi Hideaki MaedaShigeharu Morooka 《Journal of membrane science》1996
Silica-polyimide microcomposite membranes were prepared on γ-alumina-coated α-alumina support tubes, and their gas permeation properties were evaluated with He, N2 and CO2. Smoothing of the substrate surface and hybridization of silica and polyamic acid were both effective to form defect-free thin composite membranes. The CO2 permeance of a membrane with a silica content of 68 wt% was one order of magnitude higher than that of a polyimide membrane having the same thickness. The permselectivity of CO2 to N2 was 30 at 30°C and 13 at 100°C. Contributions of the silica and polyimide phases to permeance of the composite membrane were analyzed with a two-phase permeation model. The effective thickness of the rate-controlling polyimide phase was less than one-tenth of the total thickness of the silica-polyimide membrane. 相似文献
5.
Victor V. Borovkov Michael Anikin Kiyotaka Wasa Yoshiteru Sakata 《Photochemistry and photobiology》1996,63(4):477-482
Abstract— Structurally controlled aggregation course for five porphyrins (etioporphyrin [EP], 5-mono- and 5,15-di-[ p -tol-yl]etioporphyrin [TP and DTP], 5,10,15,20-tetrakis[ p -tol-y1]porphin [TTP], and 5,10,15,20-tetrakis[3,5-di- tert -bu-tylphenyl]porphin [TBP]) in dipalmitoyl-phosphatidyl-choline liposomes has been monitored by fluorescence and absorption spectroscopy. While TBP shows no tendency to aggregate in liposomes, EP, TP, DTP and TTP form a porphyrin-enriched domain in membrane interior with time. The further aggregation steps within porphyrin clusters resulting in formation of stacked porphyrin aggregates have been observed for EP, TP and DTP. 相似文献
6.
Ramaswamy K Saito H Murakami H Shiba K Suga H 《Journal of the American Chemical Society》2004,126(37):11454-11455
Fx3 is an artificial ribozyme with the ability to aminoacylate various tRNAs with phenylalanine and its nonnatural derivatives. Herein we report a simple strategy to build tRNA specificity into the generic Fx3, by appending to its 3'-end a tRNA-specific sequence (TSS), which is complementary to the acceptor stem of the cognate tRNA. This new designer ribozyme, referred to as Fx10, is able to recognize its cognate tRNA via a 10-base-pair interaction that is formed after the invasion of the tRNA acceptor stem by the TSS. We have demonstrated that Fx10 can aminoacylate its cognate tRNA with a high degree of specificity and also discriminate against the noncognate tRNAs. Because the tRNA specificity can be easily programmed into Fx10, it is a custom-made catalyst to generate nonnatural aminoacyl-tRNAs. 相似文献
7.
Kiyotaka Shigehara Haruo Matsunaga Eishun Tsuchida 《Journal of polymer science. Part A, Polymer chemistry》1978,16(8):1853-1863
Some polymeric azine or thiazine dyes were prepared by radical polymerization of dye monomers or by polymer reactions between dyes and suitable prepolymers, and their photoredox reactivities were studied. The thionine polymers containing labile ? OH groups exhibited photochromism and thermochromism, which were extremely sensitive to the moisture content of the polymer film. The reversibility of the photochromism and thermochromism increased with the water content in the film. The water-soluble polymeric dyes were photobleached under the influence of suitable reducing agents. The degree of photobleaching was smaller than for the monomeric systems except for the dye polymers containing ? OH groups, probably because of the large steric hindrance of the polymers. 相似文献
8.
M. Imoto S. Kusumoto T. Shiba E.Th. Rietschel C. Galanos O. Lüderitz 《Tetrahedron letters》1985,26(7):907-908
The chemical structure of E. coli lipid A was elucidated to be by determination of the nature of the individual acyl groups bound to the two hydroxyl groups in positions 3,3′ and the two amino groups of the D-glucosamine disaccharide phosphate backbone. 相似文献
9.
Antibiotic althiomycin was totally synthesized from d-cysteine via the procedures of the coupling with sodium salt of pyrrolinone, hydroxymethylation, and the coupling with the thiazole part, successively. 相似文献
10.
Certain amides and thioamides can easily be methylated with diazomethane in the presence of silica gel. 相似文献