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11.
Otaka A Watanabe J Yukimasa A Sasaki Y Watanabe H Kinoshita T Oishi S Tamamura H Fujii N 《The Journal of organic chemistry》2004,69(5):1634-1645
A samarium diiodide (SmI(2))-mediated reduction of gamma,gamma-difluoro-alpha,beta-enoates (15, 29, and 34) was successfully applied to the synthesis of (Z)-fluoroalkene dipeptide isosteres (23, 30, and 35), which have served as potential dipeptide mimetics. Reduction of the gamma,gamma-difluoro-alpha,beta-enoates by SmI(2) proceeded via successive two-electron transfers to form dienolate species which upon kinetically controlled trapping with t-BuOH yielded Xaa-Gly-type fluoroalkene isosteres exemplified by 23, 30, and 35. Replacement of the t-BuOH kinetic trapping agent with aldehydes or ketones provided access to alpha-substituted fluoroalkene isosteres (43 and 45) through aldol reactions of Sm-dienolates with the carbonyl compounds. Of particular note, the use of the SmI(2)-HCHO reagent system with chiral enoate 34 provided D-Phe-psi[(Z)-CF[double bond]CH]-D/L-Ser isosteres (45), which could be converted to enantiomerically pure isosteres (49-52) that bore a variety of side chain functionalities at the alpha-position. This was achieved by a sequence of manipulations consisting of beta-lactone formation followed by chromatographic separation and ring-opening with soft nucleophiles. Included in the present work is the first utilization of a Rh-catalyzed Reformatsky reaction of chiral imines for the stereoselective preparation of alpha,alpha-difluoro-beta-amino acid derivatives (28 and 33). The appropriate choice of reagents (carbonyl compounds for kinetic trapping or ring-opening nucleophiles and imines for Reformatsky reactions) allows the presented methodology to yield various fluoroalkene isosteres possessing a wide range of side chain functionalities. 相似文献
12.
Kazuhiro Watanabe Noboru Akino Tetsuo Aoyagi Noboru Ebisawa Yukio Fujiwara Atsusi Honda Takashi Inoue Takao Itoh Mikito Kawai Minoru Kazawa Junichi Koizumi Masaaki Kuriyama Kenji Miyamoto Naoki Miyamoto Kazuhiko Mogaki Yoshihiro Ohara Tokumichi Ohga Yoshikazu Okumura Hiroshi Oohara Katsumi Ohshima Fujio Satoh Kazuhiko Shimizu Syunji Takahashi Hirotsugu Usami Katsutomi Usui Masahiro Yamamoto Takeshi Yamazaki 《Radiation Physics and Chemistry》1997,49(6):631-639
A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D− ion beam. In the preliminary experiment using one ion source, a D− ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D− beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/ID− < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H− ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator. 相似文献
13.
Air containing particulate material was passed continuously for one month through a low-volume air sampler equipped with a cyclone to exclude particulates greater than 10 μm in diameter. The samples and filters were ashed in a low-temperature plasma and, after addition of In2O3 support, palladium internal standard and graphite buffer, the ashes were analyzed by a.c. are emission spectrometry. Standard samples were prepared from a commercial standard containing 49 elements. The procedure allows the determination of 14 trace metals (Ag, Al, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Sn, Ti, V, Zn) with relative standard deviations of 1.4–15.1%. The procedure has been applied successfully to monthly determinations of the average atmospheric concentrations of these elements in Kobe City for the past three years. 相似文献
14.
15.
Tadamichi Hirabayashi Yoshikazu Nishikawa Kenji Yokota 《Journal of polymer science. Part A, Polymer chemistry》1979,17(12):3823-3833
The alternating copolymerization of 1- and 2-vinylnaphthalene (1-VNap and 2-VNap) with methyl methacrylate (MMA) by using diethylaluminum chloride (Et2AlCl) in toluene at 0°C has been studied. No polymerization could occur without Et2AlCl, and alternating copolymers were obtained only when an equimolar amount of Et2AlCl with MMA was supplied. Through 1H-NMR analyses on both dyad and triad of alternating deuterated 1- and 2-α-d-VNap–MMA copolymers, each configuration could be described successfully by a single parameter, coisotacticity σ, whose value was estimated as 0.41 for the former and 0.56 for the latter copolymer, respectively. A rather low coisotacticity of copoly(1-VNap–MMA) was explained in the terms of steric effect (peri effect) of 1-VNap monomer. 相似文献
16.
Yoshikazu Shizuri Yoshishige Okuno Hideyuki Shigemori Shosuke Yamamura 《Tetrahedron letters》1987,28(52):6661-6664
(±)-8,14-Cedranoxide has been synthesized starting from 3,4-dimethoxyphenol, wherein 6-acetoxymethyl-2,6-dimethyl-9-methoxytricyclo[5.3.1.01,5]undec-9-en-8,11-dione as a key intermediate has been produced efficiently by means of electrochemical methods. 相似文献
17.
Muranaka A Okuda M Kobayashi N Somers K Ceulemans A 《Journal of the American Chemical Society》2004,126(14):4596-4604
Oxo-titanium phthalocyanine (TiOPc) derivatives of catechin and hematoxylin (natural ortho-diol type chiral compounds) have been prepared and characterized by spectral and chromatographic techniques. It is demonstrated that the TiOPc unit is an excellent template for chiral recognition through its isolated Q-transitions. The formation of a helical dimeric complex with hematoxylin induces strong CD-activity in the Q-band region. Ab initio geometry optimizations were combined with a Kuhn-Kirkwood coupled-oscillator mechanism to obtain the absolute configuration of hematoxylin. In addition, it is shown that the described chiroptical recognition method is sensitive to slight conformational changes. 相似文献
18.
Munam Lee Yoshikazu Ishida Yuji Minoura 《Journal of polymer science. Part A, Polymer chemistry》1982,20(2):457-465
The “living” radical polymerization of methyl methacrylate with the aged Cr2+ plus benzoyl peroxide (BPO) system in the presence of various amines as ligand has been studied in N,N′-dimethylformamide. Aliphatic amines such as ethylenediamine diminished the rate of polymerization, while dipyridyl (dipy) and o-phenanthroline (phen) accelerated the polymerization rate as follows: phen > dipy > pyridine ? none. Specifically, the rate of polymerization in the presence of phen had a maximum value at [phen]/[Cr2+] = 0.5. The retardation of polymerization by aliphatic amines was explained by the interaction of BPO with free and coordinated amines. The latter result may support the mechanism involving the complexed radical proposed for the living radical polymerization with the aged Cr2+ + BPO system. In the presence of phen the effects of aging period and aging temperature as well as polymerization temperature were studied and the nature of complexed radicals is discussed. 相似文献
19.
Muranaka A Matsumoto Y Uchiyama M Jiang J Bian Y Ceulemans A Kobayashi N 《Inorganic chemistry》2005,44(11):3818-3826
A series of heteroleptic rare-earth sandwich complexes [M(Nc)(OEP)] (M = La, Nd, Eu, Dy, and Lu; Nc = 2,3-naphthalocyaninate; OEP = octaethylporphyrinate) have been investigated by electronic absorption and magnetic circular dichroism (MCD) spectroscopy. The electronic absorption spectra of the neutral forms showed two characteristic transitions (bands I and II) in the near-IR region, both of which were systematically shifted depending on the size of their central metal. In the MCD spectra, a relatively intense Faraday A term and a significantly weak Faraday B term have been observed corresponding to bands II and I, respectively. The spectral features were successfully interpreted using a simple MO model by considering the relevant interactions of Gouterman's four orbitals of the constituent chromophores. The model succeeded in assigning the MCD spectra of the related compounds, the oxidized and reduced forms of the dimer ([M(Nc)(OEP)]+ and [M(Nc)(OEP)]-), and neutral forms of the triple-decker compounds (M2(Nc)(OEP)2, M = Nd, Eu). DFT calculations of the dimers supported the validity of this model. 相似文献
20.
Kazuhiro Kobayashi Hiroyasu Takeuchi Shinzo Seko Yoshikazu Kanno Sachiko Kujime Hiroshi Suginome 《Helvetica chimica acta》1993,76(8):2942-2950
The 2,3-dihydro-1H-benz[f]indole-4,9-diones 3a–d , h were formed in a one-step reaction in 13–82% yield by an unprecedented [3 + 2] regioselective photoaddition of 2-amino-1,4-naphthoquinone ( 1 ) with various electronrich alkenes 2 (Scheme 1, Table). The [3 + 2] photoadducts derived from 1 with vinyl ethers and vinyl acetate gave 1H-benz[f]indole-4,9-diones 4e , f , i , in 33–72% yield, by spontaneous loss of the corresponding alcohol or AcOH from the resulting adducts; 4i has a kinamycin skeleton. The [3 + 2] photoaddition also took place on irradiation of the differently substituted amino-1,4-benzoquinones 6 , 7 , and 12 and excess alkenes 2 in benzene, giving 1H-indole-4,7-dione derivatives 13 and 14 (Scheme 3), 15a and 16 (Scheme 4), and 18 (Scheme 4), respectively. The initial products in these photoadditions were proved to be hydroquinones, the air oxidation of which yielded the heterocyclic quinones; 2,3-dihydro-2-methoxy-2-methyl-5-phenyl-1H-indole-1,4,7-triyl triacetate ( 19 ) was isolated after treatment of the crude photoaddition mixture obtained from 2-amino-5-phenyl-1,4-benzoquinone ( 7 ) and 2-methoxyprop-1-ene ( 2f ) with Ac2O and pyridine under N2. A pathway leading to the annelated hydroquinones involving ionic intermediates arising from an electron transfer in these photoadditions is proposed (Scheme 5). 相似文献