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71.
Anna Miyazaki Yoshifumi Tachibana Eibai Lee Gyongyi Bokonyi Yuko Tsuda Yoshio Okada 《Tetrahedron letters》2004,45(33):6323-6327
It was reported that the somatostatin analog TT-232, d-Phe-c(Cys-Tyr-d-Trp-Lys-Cys)-Thr-NH2, exhibited a highly potent antitumor activity in vitro and in vivo. Using pyrazinone analogs and aliphatic amino acids instead of the disulfide bond, we prepared novel type somatostatin analogs including the sequence essential for antitumor activities, Tyr-d-Trp-Lys. These analogs exhibited antiproliferative effect on A431 tumor cells. 相似文献
72.
Ozeki H Nomoto A Ogawa K Kobuke Y Murakami M Hosoda K Ohtani M Nakashima S Miyasaka H Okada T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(24):6393-6401
We synthesized special-pair/electron-acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl-substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole pi system of the dimer. Time-resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped cofacial dimer relative to that of the monomeric system demonstrates the significance of the special-pair arrangement for efficient charge separation in photosynthesis. 相似文献
73.
In the presence of CuCN, reaction of γ,γ-dialkoxyallylic zirconium species 1 with imines proceeded at the γ-position of 1 to give gem-dialkoxyhomoallylic amines 3 in high yield. In this reaction, γ,γ-dialkoxyallylic zirconium species 1 acts as an α,β-unsaturated acyl anion equivalent. 相似文献
74.
Yoshio Tanaka Morishige Atsukawa Yukio Shimura Akira Okada Hideki Sakuraba Tokuji Sakata 《Journal of polymer science. Part A, Polymer chemistry》1975,13(5):1017-1028
A soluble and self-crosslinkable linear copolymer with pendant epoxy and pyridyl groups was obtained from glycidyl methacrylate (M1) and 2-vinylpyridine (M2) or 2-vinyl-5-ethylpyridine (M2) by the action of azobisisobutyronitrile. The monomer reactivity ratios were determined in tetrahydrofuran at 60°C: r1 = 0.510, r2 = 0.620 with 2-vinylpyridine and r1 = 0.57, r2 = 0.62 with 2-vinyl-5-ethylpyridine. These were consistent with the calculated values with the reported Q and e values for these monomers. The intrinsic viscosities of the copolymers with 2-vinylpyridine and with 2-vinyl-5-ethylpyridine were found to be 0.17–0.19 and 0.26–0.38, respectively, in tetrahydrofuran at 30°C; they were independent of the copolymer composition. The copolymers were amorphous, had no clear melting points, and became insoluble crosslinked polymers under heating without further addition of any curing agents. 相似文献
75.
A cross-linked 1,3,5-tristyrylbenzene dendrimer 5 was synthesized to study the photochemical isomerization mechanism. On irradiation, 5 isomerized with the quantum yields (ΦE→Z) of 0.063, which was not very much different from that for a model compound 1 (ΦE→Z 0.080), supporting a volume-conserving hula-twist (HT) mechanism during the photochemical E-Z isomerization. 相似文献
76.
Boller TM Murphy JM Hapke M Ishiyama T Miyaura N Hartwig JF 《Journal of the American Chemical Society》2005,127(41):14263-14278
This paper describes mechanistic studies on the functionalization of arenes with the diboron reagent B(2)pin(2) (bis-pinacolato diborane(4)) catalyzed by the combination of 4,4'-di-tert-butylbipyridine (dtbpy) and olefin-ligated iridium halide or olefin-ligated iridium alkoxide complexes. This work identifies the catalyst resting state as [Ir(dtbpy)(COE)(Bpin)(3)] (COE = cyclooctene, Bpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl). [Ir(dtbpy)(COE)(Bpin)(3)] was prepared by independent synthesis in high yield from [Ir(COD)(OMe)](2), dtbpy, COE, and HBpin. This complex is formed in low yield from [Ir(COD)(OMe)](2), dtbpy, COE, and B(2)pin(2). Kinetic studies show that this complex reacts with arenes after reversible dissociation of COE. An alternative mechanism in which the arene reacts with the Ir(I) complex [Ir(dtbpy)Bpin] after dissociation of COE and reductive elimination of B(2)pin(2) does not occur to a measurable extent. The reaction of [Ir(dtbpy)(COE)(Bpin)(3)] with arenes and the catalytic reaction of B(2)pin(2) with arenes catalyzed by [Ir(COD)(OMe)](2) and dtbpy occur faster with electron-poor arenes than with electron-rich arenes. However, both the stoichiometric and catalytic reactions also occur faster with the electron-rich heteroarenes thiophene and furan than with arenes, perhaps because eta(2)-heteroarene complexes are more stable than the eta(2)-arene complexes and the eta(2)-heteroarene or arene complexes are intermediates that precede oxidative addition. Kinetic studies on the catalytic reaction show that [Ir(dtbpy)(COE)(Bpin)(3)] enters the catalytic cycle by dissociation of COE, and a comparison of the kinetic isotope effects of the catalytic and stoichiometric reactions shows that the reactive intermediate [Ir(dtbpy)(Bpin)(3)] cleaves the arene C-H bond. The barriers for ligand exchange and C-H activation allow an experimental assessment of several conclusions drawn from computational work. Most generally, our results corroborate the conclusion that C-H bond cleavage is turnover-limiting, but the experimental barrier for this bond cleavage is much lower than the calculated barrier. 相似文献
77.
High enantioselectivity in rhodium-catalyzed allylic alkylation of 1-substituted 2-propenyl acetates
[reaction: see text] Rhodium-catalyzed asymmetric allylic alkylation of 1-substituted 2-propenyl acetates with dimethyl malonate proceeded with high enantioselectivity in the presence of cesium carbonate as a base and a rhodium catalyst generated from Rh(dpm)(C(2)H(4))(2) (dpm = dipivaloylmethanato) and a chiral phosphino-oxazoline whose basic skeleton is axially chiral binaphthyl to give branch alkylation products in greater than 90% ee. 相似文献
78.
Shunsuke Hayashi Takashi Ishikawa Tatsuo Asai Colin Turnbull Kanzo Sakata Koji Ogawa 《Tetrahedron》2004,60(33):7005-7013
The hydrolysis of 2-phenylethyl β-d-glucopyranoside (3) was found to be partially inhibited by feeding with 2-phenyl-N-glucosyl-acetamidiumbromide (8), a β-glucosidase inhibitor, resulting in a decrease in the diurnal emission of 2-phenylethanol (2) from Rosa damascena Mill. flowers. Detection of [1,1,2,2′,3′,4′,5′,6′-2H8]-2 and [1,2,2′,3′,4′,5′,6′-2H7]-2 from R. ‘Hoh-Jun’ flowers fed with [1,1,2,2′,3′,4′,5′,6′-2H8]-3 suggested that β-glucosidase, alcohol dehydrogenase, and reductase might be involved in scent emission. Comprehensive GC-SIM analyses revealed that [1,2,2,2′,3′,4′,5′,6′-2H8]-2 and [1,2,2,2′,3′,4′,5′,6′-2H8]-3 must be biosynthesized from [1,2,2,2′,3′,4′,5′6′-2H8] l-phenylalanine ([2H8]-1) with a retention of the deuterium atom at α-position of [2H8]-1. 相似文献
79.
N Teno K Wanaka Y Okada Y Tsuda U Okamoto A Hijikata-Okunomiya T Naito S Okamoto 《Chemical & pharmaceutical bulletin》1991,39(11):2930-2936
Specific plasma kallikrein inhibitors were designed and synthesized and their structure-activity relationship was studied. trans-4-Aminomethylcyclohexanecarbonyl (Tra)-lysyl-4-ethoxycarbonylanilide inhibited plasma kallikrein and plasmin with IC50 values of 23 and 210 microM, respectively, indicating that this compound is fairly specific to plasma kallikrein. Tra-arginyl-4-ethoxycarbonylanilide inhibited plasma kallikrein and plasmin with IC50 values of 16 and 480 microM, respectively. Tra-homoarginyl-4-carboxyanilide inhibited plasma kallikrein and plasmin with IC50 values of 14 microM and 1 mM, respectively. Finally, Tra-Arg(Mts)-4-acetylanilide (ACA) exhibited potent and selective inhibitory activity against plasma kallikrein (IC50 value for plasma kallikrein: 2 microM and for plasmin: 42 microM). 相似文献
80.
Yoshida N Ishizuka T Yofu K Murakami M Miyasaki H Okada T Nagata Y Itaya A Cho HS Kim D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(12):2854-2866
A series of zinc(II) porphyrin-imide dyads (ZP-Im), in which an electron donating ZP moiety is directly connected to an electron accepting imide moiety in the meso position, have been prepared for the examination of energy gap dependence of intramolecular electron transfer reactions with large electronic coupling. The nearly perpendicular conformation of the imide moiety towards the porphyrin plane has been revealed by Xray crystal structures. The energy gap for charge separation, 1ZP* - Im --> ZP+ - Im-, is varied by changing the electron accepting imide moiety to cover a range of about 0.8 eV in DMF. Definitive evidence for electron transfer has been obtained in three solvents (toluene, THF, and DMF) through picosecond-femtosecond transient absorption studies, which have allowed us to determine the rates of photoinduced charge separation, 1ZP* - Im --> ZP+ - Im-, and subsequent thermal charge recombination ZP+ - Im- --> ZP - Im. The free-energy gap dependence (energy gap law) has been probed from the normal to the nearly top region for the charge separation rate alone, and only the inverted region for the charge recombination rate. Although both of the energy gap dependencies can be approximately reproduced by means of the simplified semiclassical equation, when we take into consideration the effect of the high frequency vibrations replaced by one mode of averaged frequency, many features, including the effects of solvent polarity and the electron tunneling matrix element on the energy gap law, differ considerably from those of the previously studied porphyrin-quinone systems, which have weaker interchromophore electronic interactions. 相似文献