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51.
H Harada J Kazami S Watanuki R Tsuzuki K Sudoh A Fujimori T Tokunaga A Tanaka S Tsukamoto I Yanagisawa 《Chemical & pharmaceutical bulletin》2001,49(12):1593-1603
In the previous paper, we described a series of the 2-arylethenesulfonamide derivatives, a novel class of ETA-selective endothelin (ET) receptor antagonists, including the compounds 1a, b. Compound 1a showed excellent oral antagonistic activities and pharmacokinetic profiles, and the monopotassium salt of 1 (YM-598 monopotassium) is in clinical trials. In this paper, we wish to report the investigation of the further details of structure-activity relationships (SARs) of the 2-phenylethenesulfonamide region in 1a. It was found that methyl substitutions at the 2-, 4- and 6-positions of the phenyl group in 1a led to the discovery of the ET(A)/ET(B) mixed antagonist (6s) with an IC50 of 2.2 nM for the ET(A) receptor. We also found that introduction of an ethyl group to the 1-position of the ethenyl group in 1a gave the ET(A) selective antagonist (6u) with an oral endothelin antagonistic activity in rats. 相似文献
52.
Dr. Keishiro Tahara Nazuna Terashita Dr. Ken Tokunaga Shiomi Yabumoto Prof. Jun-ichi Kikuchi Dr. Yoshiki Ozawa Prof. Masaaki Abe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13728-13738
Realization of molecular quantum cellular automata (QCA), a promising architecture for molecular computing through current-free processes, requires improved understanding and application of mixed-valence (MV) molecules. In this report, we present an electrostatic approach to creating MV subspecies through internalizing opposite charges in close proximity to MV ionic moieties. This approach is demonstrated by unsymmetrically attaching a charge-responsive boron substituent to a well-known organometallic MV complex, biferrocenium. Guest anions (CN− and F−) bind to the Lewis acidic boron center, leading to unusual blue-shifts of the intervalence charge-transfer (IVCT) bands. To the best of our knowledge, this is the first reported example of a zwitterionic MV series in which the degree of positive charge delocalization can be varied by changing the bound anions, and serves to clarify the interplay between IVCT parameters. The key underlying factor is the variable zero-level energy difference in the MV states. This work provides new insight into imbuing MV molecules with external charge-responsiveness, a prerequisite of molecular QCA techniques. 相似文献
53.
Prof. Dr. Kennosuke Itoh Shun-ichi Nagao Prof. Dr. Ken Tokunaga Dr. Shigeto Hirayama Dr. Fumika Karaki Dr. Takaaki Mizuguchi Dr. Kenichiro Nagai Noriko Sato Dr. Mitsuaki Suzuki Prof. Dr. Masashi Hashimoto Prof. Dr. Hideaki Fujii 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5171-5179
1,2,3,4-Tetrahydroquinolines should be applicable to the development of new pharmaceutical agents. A facile synthesis of 1,2,3,4-tetrahydroquinolines that is achieved by a photoinduced formal [4+2] cycloaddition reaction of acyclic α,β-unsaturated amides and imides with N,N-dialkylanilines under visible-light irradiation, in which a new IrIII complex photosensitizer, a thiourea, and an oxidant act cooperatively in promoting the reaction, is reported. The photoreaction enables the synthesis of a wide variety of 1,2,3,4-tetrahydroquinolines, while controlling the trans/cis diastereoselectivity (>99:1) and constructing contiguous stereogenic centers. A chemoselective cleavage of an acyclic imide auxiliary is demonstrated. 相似文献
54.
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56.
Yasushi Koyama Hiroaki Nakasu Yumiko Mukai Fumio Tokunaga 《Photochemistry and photobiology》1993,57(4):732-738
Abstract— The dependence of the isomeric configuration of the retinylidene chromophore of bacteriorhodopsin on the pH value and on the wavelength of irradiation (in a photostationary state) were examined by high performance liquid chromatographic analyses of extracted retinal. The process of isomerization of the chromophore during light adaptation was also traced. More than 93% of all- trans and less than 5% of 13- cis retinal were extracted in the photostationary state for irradiation at 560 nm in the pH region of5–9 as well as for irradiation in the wavelength region of 400–650 nm at pH 7. Comparison of the above photostationary state composition with that of protonated n -butylamine Schiff base of retinal indicates that strong constraint is applied to the chromophore by the apo-protein. The constraint can be changed at low or high pH by a partial denaturation or transition of the apo-protein, which results in the generation of 11- cis retinal in the extract. At higher photon density, the isomerization process of the chromophore during light adaptation at pH 7 was characterized, as extracted isomeric retinal, by (1) the initial decrease in 13- cis and increase in all- trans , (2) a subsequent, transient toward the above photostationary state composition. The results are discussed in terms of both the photoisomerization pattern inherent in the retinylidene chromophore and the control by the apo-protein. 相似文献
57.
Abstract— The artificial pigments of bacteriorhodopsin (bR) were synthesized with retinal analogues which have 6-s-cis fixed conformation. In order to study the shape of binding pocket around β-ionone ring of retinal, we used three different 6-s-cis fixed retinals (1–3), which have a gem-dimethyl group at a different position of the ring structure. These three 6-s-cis fixed retinals produced bR analogue pigments with absorption maxima at 574, 594 and 584 nm, respectively. These analogue pigments showed proton pumping activities upon incorporation into vesicles, indicating that 6-s-trans structure of retinal is not necessary to pump protons. Although these retinal analogues possess the same conjugated π-electron systems, the wavelengths of maximum absorbance of the analogue pigments were different from each other, indicating a distinctly steric interaction between retinal ring portion and apoprotein. The analogue pigments were also different from each other in regeneration rate and the number of the final products. These differences resulted from a difference in the position of the dimethyl substituent at the ring structure. Based on the results the molecular structure around β-ionone ring of retinal-binding pocket was discussed. 相似文献
58.
Toshihiko Oka Hironari Kamikubo Fumio Tokunaga Janos K. Lanyi Richard Needleman Mikio Kataoka 《Photochemistry and photobiology》1997,66(6):768-773
Abstract— The single cysteine-containing bacteriorhodopsin mutants F27C, L100C, T170C, F171C and I222C were labeled with p -chloromercuribenzoic acid, which specifically reacts with sulfhydryl groups. These cysteines should be located at the cytoplasmic ends of the transmembrane helices A, C, F or G. We determined the positions of the bound mercury atoms by X-ray diffraction of purple membrane films, with better than 1 Å accuracy. The determined mercury positions were compared with the structural model from cryoelectron microscopy (N. Grigorieff, T. A. Ceska, K. H. Downing, J. M. Baldwin and R. Henderson, J. Mol. Biol 259, 393-421, 1996). Given that the distance between the mercury and the Cα atom of the cysteine in the xy plane must be shorter than 4.5 Å and that the mercury atom is located at the δ position, the positions obtained for the mercury labels agree with their expected positions from the structural model. The present results give a rationale for detecting structural changes upon illumination as shifts occur in the mercury label position. 相似文献
59.
Nishiyama Y Kawamatsu H Funato S Tokunaga K Sonoda N 《The Journal of organic chemistry》2003,68(9):3599-3602
A new synthetic method of organoselenium compounds has been developed. When phenyl tributylstannyl selenide (PhSeSnBu(3)) was allowed to react with acyl or aroyl chlorides in the presence of a catalytic amount of a palladium complex such as Pd(PPh(3))(4), Se-phenyl selenol esters were obtained in moderate to good yields. Similarly, the palladium complex catalyzed the reaction of PhSeSnBu(3) with alpha-halo carbonyl compounds to afford the corresponding alpha-phenyseleno carbonyl compounds in moderate yields. 相似文献
60.
[reaction: see text] Oligomerization of Pd(OAc)2(L)2 (L = pyridine derivatives), a catalyst for the air oxidation of alcohols, is studied with MALDI TOF mass, using dithranol as the matrix. The degree of the Pd oligomerization is influenced by the pyridine ligands, and this ligand effect is similar to one observed for Pd black formation in the catalysis. 相似文献