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排序方式: 共有283条查询结果,搜索用时 15 毫秒
61.
Iida A Takai K Okabayashi T Misaki T Tanabe Y 《Chemical communications (Cambridge, England)》2005,(25):3171-3173
We have developed a practical crossed Claisen condensation between ketene silyl acetals and methyl esters using catalytic NaOH to obtain alpha-monoalkylated beta-keto esters and inaccessible alpha,alpha-dialkylated beta-keto esters. 相似文献
62.
63.
Highly efficient esterification of carboxylic acids with alcohols by montmorillonite-enwrapped titanium as a heterogeneous acid catalyst 总被引:1,自引:0,他引:1
Tomonori KawabataTomoo Mizugaki Kohki EbitaniKiyotomi Kaneda 《Tetrahedron letters》2003,44(51):9205-9208
Montmorillonite-enwrapped titanium catalyst was found to efficiently promote the esterification of carboxylic acids with alcohols. In comparison to other catalysts reported to date, this heterogeneous catalyst offers a remarkably simple workup procedure, and is reusable without any appreciable loss in its activity and selectivity. 相似文献
64.
Kazunobu Toshima Tomonori KimuraRyusuke Takano Tomohiro OzawaAkiko Ariga Yutaka ShimaKazuo Umezawa Shuichi Matsumura 《Tetrahedron》2003,59(35):7057-7066
The quinoxaline moiety in antitumor quinoxaline antibiotics cleaved double stranded DNA at the 5′ side guanine of the 5′-GG-3′ site upon irradiation with UV light with a long wavelength and without any additive. The quinoxaline-carbohydrate hybrid system was very effective for the DNA cleavage. Furthermore, the quinoxaline-carbohydrate hybrids exhibited strong and selective cytotoxicity against cancer cells with photoirradiation. 相似文献
65.
Maekawa Y Inaba T Hobo H Narita T Koshikawa H Moon S Kato J Yoshida M 《Chemical communications (Cambridge, England)》2002,(18):2088-2089
Radiation-induced reactions of cinnamic acid derivatives have been examined and compared with photoreactions in the crystalline state; all the reaction products were exactly the same as those of the photoreactions, indicating that the reactions proceed only via the lowest excited state to give [2 + 2] cycloadducts, E/Z isomerization products, or starting molecules. 相似文献
66.
67.
Takashi Katsu Tomonori Imamura Keiko Komagoe Kazufumi Masuda Tohru Mizushima 《Analytical sciences》2007,23(5):517-522
The changes induced by biologically active substances in the permeability to K+ and calcein of liposomes composed of egg phosphatidylcholine and cholesterol were measured simultaneously in order to rapidly screen the sizes of pores formed in a membrane, using different sized markers. The substances examined in the present study were classified into three types based on differences in the rates at which K+ and calcein were released. The first type released only K+, and included gramicidin A. The second type predominantly released K+, preceding the release of calcein, and included amphotericin B and nystatin. The third type, including antimicrobial peptides, such as gramicidin S, alamethicin, and melittin, and several membrane-active drugs, like celecoxib (non-steroidal anti-inflammatory drug), 1-dodecylazacycloheptan-2-one (named azone; skin permeation enhancer), and chlorpromazine (tranquilizer), caused the release of K+ and calcein simultaneously. Thus, the sizes of pores formed in a liposomal membrane increased in the following order: types one, two, and three. We determined the size more precisely by conducting an osmotic protection experiment, measuring the release of calcein in the presence of osmotic protectants of different sizes. The radii of pores formed by the second type, amphotericin B and nystatin, were 0.36 - 0.46 nm, while the radii of pores formed by the third type were much larger, 0.63 - 0.67 nm or more. The permeability changes induced by substances of the third type are discussed in connection with a transient pore formed in a lipid packing mismatch taking place during the phase transition of dipalmitoylphosphatidylcholine liposomes. 相似文献
68.
Das Kaustav Yuasa Tomonori Nishidate Izumi Funamizu Hideki Aizu Yoshihisa 《Optical Review》2020,27(2):233-245
Optical Review - This paper presents a numerical study on simulated spectra and point spread functions in the database that we constructed by moderate grouping of nine layers in a skin model. The... 相似文献
69.
Tomonori Ichibakase Tetsuya Kaneko Yuya Orito Shunsuke Kotani Makoto Nakajima 《Tetrahedron》2012,68(22):4210-4224
The aldol reactions of trimethoxysilyl enol ethers catalyzed by lithium binaphtholate were found to be powerful tools for the construction of quaternary asymmetric carbon centers. The stereoselectivities were greatly affected by the presence of water. Trimethoxysilyl enol ether derived from a cyclic ketone, such as cyclohexanone, was used as a substrate to obtain the anti-adduct preferentially under anhydrous conditions; by contrast, the syn-adduct was preferentially obtained under aqueous conditions with high stereoselectivity. The aldol-Tishchenko reaction of a trimethoxysilyl enol ether derived from acyclic ketones proceeded to give monoacyl 1,3-diol derivatives in high enantioselectivities. 相似文献
70.
Xanthones and acridones were synthesized from 3,4-difluoronitrobenzene and 2-fluorobenzaldehydes in two or three steps. The key step was nucleophilic aroylation catalyzed by imidazolidenyl carbene. The nucleophilic aroylation of 3,4-difluoronitrobenzene afforded 2,2'-difluoro-4-nitrobenzophenones. The cyclization of the difluorobenzophenones with O-nucleophile and N-nucleophile yielded 3-nitroxanthones and 3-nitroacridones, respectively. Indazole, quinolino[2,3-b]quinoxaline, and thianaphtho[2,3-b]quinoxaline derivatives were also synthesized via nucleophilic aroylation of 2,3-dichloroquinoxaline followed by cyclization with nucleophiles. 相似文献