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51.
Spirodienones bearing the 1-azaspiro[4.5]decane ring system have been synthesized from N-methoxy-(4-halogenophenyl)amides by the intramolecular ipso attack of a nitrenium ion generated with [hydroxy(tosyloxy)iodo]benzene in trifluoroethanol. 相似文献
52.
Bhalchandra M. BhanageShin-ichiro Fujita Takeshi YoshidaYoko Sano Masahiko Arai 《Tetrahedron letters》2003,44(17):3505-3507
Using the form of supported liquid-phase catalysts, two or more homogeneous catalysts can simultaneously be used with retaining their own activities and taking the advantage of catalyst-product separation and catalyst recycling. 相似文献
53.
Takeshi Shimomura Tatsuya Funaki Kohzo Ito Byoung-Ki Choi Tomihiro Hashizume 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):275-278
We have investigated the inclusion properties of molecular nanotubes composed ofcrosslinked -cyclodextrin. Induced circular dichroism was used to probe theformation and dissociation of complexes between the nanotubes and azobenzenemodified linear polymers. The polymer was poly(ethylene glycol) (PEG), either withor without a hydrophobic alkyl chain.It was found that the inclusion complex betweenthe nanotubes and polymers formed at room temperature, and that the polymers dissociated from the nanotubes with increasing temperature. Further, the polymer with hydrophobic alkyl chain was bound inside the nanotube more strongly and dissociated more abruptly with increasing temperature than its hydrophilic counterpart as expected theoretically. 相似文献
54.
Axially chiral benzamides and anilides were prepared by enantiotopic lithiation at the distinguished benzylic methyl of prochiral tricarbonylchromium complexes of N,N-diethyl 2,6-dimethylbenzamide (1) and N-methyl-N-acyl 2,6-dimethylaniline (14 and 21) with a chiral lithium amide base followed by electrophilic substitution in good yields with high optical purity. The resulting axially chiral chromium-complexed benzamides and anilides were oxidized under air to give chromium-free axially chiral benzamides and anilides in an enantiomerically active form without axial bond rotation at room temperature. 相似文献
55.
Kyoungmoo Koh Kohji Ohno Yoshinobu Tsujii Takeshi Fukuda 《European Polymer Journal》2004,40(12):2665-2670
Copper-mediated atom transfer radical polymerization (ATRP) of a protected silanol group-holding methacrylate, methacryloxypropyltrimethoxysilane (MOPS), was investigated. In a dry condition using carefully distilled solvent and monomer, the polymerization proceeded in a living fashion providing a low-polydispersity polymer with a predicted molecular weight. The ATRP in conjunction with the sequential monomer addition of methyl methacrylate (MMA) and MOPS afforded a block copolymer of the type PMMA-b-poly(MMA-r-MOPS). The heat treatment of a solution of the block copolymer in the presence of a catalytic amount of ammonia gave a polymeric core-shell nanoparticle with a shell of PMMA moieties and a core of the poly(MMA-r-MOPS) blocks cross-linked via the condensation of the trimethoxysilane groups of the MOPS moieties. 相似文献
56.
Kazuyuki MiyashitaHidenobu Murafuji Hiroshi IwakiEito Yoshioka Takeshi Imanishi 《Tetrahedron》2003,59(26):4873-4879
As a second-generation pyridoxal model compound for cystathionine β-synthase, we designed a novel model compound having an ionophore function and an imidazole function, application of which to the β-replacement reaction with various thiols smoothly took place to give S-substituted cysteines. Peptides having a serine-O-carbonate residue at the N-terminal position were also converted to the corresponding peptides having an S-substituted cysteine residue under the catalytic conditions of the novel pyridoxal model compound. 相似文献
57.
Hitomi Uno Toshikazu Takata Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1989,27(5):1675-1685
Graft copolymerization of a bicycloorthoester (BOE) with polymer-supported sulfonium salts was studied. Several polymer-supported sulfonium salts were prepared by the homopolymerizations of p-vinylbenzyl tetramethylenesulfonium hexafluoroantimonate ( 2 ) and 4-(p-vinylphenyl)butyl tetramethylenesulfonium hexafluoroantimonate ( 3 ), and by the copolymerizations of 2 with some vinyl monomers (n-butyl vinyl ether, styrene, acrylonitrile, and p-styrenesulfonic acid potassium salt). These sulfonium salts could initiate the polymerization of BOE to give grafted polymers. Temperature dependences of the catalytic activity of them were not so dramatic as that of benzyl tetramethylenesulfonium hexafluoroantimonate ( 1 ), but the activities of them were higher than that of 1 at temperatures lower than 80°C. The conversion of BOE in the polymerizations with these polymer initiators was ca. 30–70% at 120°C for 7 h. An effect of the comonomer structure on the catalytic activity was observed and styrene was the best comonomer for 2 in terms of the reactivity of the copolymer. The spacer-modified sulfonium salt (homopolymer of 3 ) was slightly lower than polymer-supported benzyl type sulfonium salt (homopolymer of 2 ) in the catalytic activity. 相似文献
58.
Shin-ichiro Shoda Yoshinori Misawa Yousuke Nishijima Yukiko Tawata Tomohiko Kotake Masato Noguchi Atsushi Kobayashi Takeshi Watanabe 《Cellulose (London, England)》2006,13(4):477-484
Chitinase-catalyzed hydrolytic and transglycosylating behavior of 1,2-oxazoline derivative of N-acetyllactosamine (LacNAc-oxa) 1 has been investigated. An extremely rapid hydrolysis (ring-opening of the oxazoline moiety) could be observed, suggesting that 1 behaves as a transition state analogue substrate for chitinase A1 (Bacillus circulans WL-12). This disaccharide monomer 1 was found to polymerize under basic conditions, giving rise to novel oligosaccharides having a β(1-4)–β(1-6) repeating unit in the main chain. The degree of polymerization of the resulting oligosaccharides was up to 5. This is the first example of enzymatic glycosylation reaction forming a β(1-6) bond catalyzed by chitinase. 相似文献
59.
Komatsu H Iwasawa N Citterio D Suzuki Y Kubota T Tokuno K Kitamura Y Oka K Suzuki K 《Journal of the American Chemical Society》2004,126(50):16353-16360
The role of intracellular magnesium ions is of high interest in the fields of pharmacology and cellular biology. To accomplish the dynamic and three-dimensional imaging of intracellular Mg2+, there is a strong desire for the development of optimized Mg2+ fluorescent probes. In this paper we describe the design, synthesis, and cellular application of the three novel Mg2+ fluorescent probes KMG-101, -103, and -104. The compounds of this series feature a charged beta-diketone as a binding site specific for Mg2+ and a fluorescein residue as the fluorophore that can be excited with an Ar+ laser such as is widely used in confocal scanning microscopy. This molecular design leads to an intensive off-on-type fluorescent response toward Mg2+ ions. The two fluorescent probes KMG-103 and -104 showed suitable dissociation constants (Kd,Mg2+ = 2 mM) and nearly a 10-fold fluorescence enhancement over the intracellular magnesium ion concentration range (0.1-6 mM), allowing high-contrast, sensitive, and selective Mg2+ measurements. For intracellular applications, the membrane-permeable probe KMG-104AM was synthesized and successfully incorporated into PC12 cells. Upon application of the mitochondria uncoupler FCCP to the probe-incorporated cells, the resulting increase in the free magnesium ion concentration could be followed over time. By using a confocal microscope, the intracellular 3D magnesium ion concentration distributions were satisfactorily observed. 相似文献
60.
Toshiyuki Chikuma Yoko ShimabukuroTakeya Iguchi Akira TanakaKyoji Taguchi Takeshi KatoMitsune Yamaguchi Hiroshi Hojo 《Analytica chimica acta》2002,457(2):157-164
A rapid and sensitive assay for the determination of Dns-His-Lys-Arg-His-Lys cleaving enzyme activity is reported. This assay is based on fluorimetric detection of a dansylated dipeptide, 5-dimethylaminonaphthalene-1-sulfonyl-His-Lys, enzymatically formed from the substrate 5-dimethylaminonaphthalene-1-sulfonyl-His-Lys-Arg-His-d-Lys, after separation by high-performance liquid chromatography (HPLC) using a C-18 reversed-phase column by isocratic elution. This assay is sensitive enough to measure 5-dimethylaminonaphthalene-1-sulfonyl-His-Lys at concentrations as low as 7 pmol, and yields highly reproducible results and requires less than 9.0 min per sample for separation and quantitation. The optimum pH for Dns-His-Lys-Arg-His-Lys cleaving enzyme activity was 7.5-8.0. The Michaelis constant (Km) and the maximum velocity (Vmax) values were 33.3 μM and 47.07 pmol/(μg h), respectively with the use of enzyme extract obtained from bovine pituitary. By using this assay, axonal transport of this enzyme activity was observed 48 h after double ligations of rat sciatic nerves. The high sensitivity and selectivity of this assay would be useful for clarification of the physiological role of this enzyme. 相似文献