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71.
Stereoselective synthesis of (3S,4S)- and (3R,4R)-series of 3,4-dihydroxyglutamic acids was investigated. The key reaction in this synthesis is asymmetric reduction of meso-imide derived from meso-tartaric acid. Lewis acid-promoted cyanation of the obtained optically active lactam via the acyliminium intermediate followed by standard deprotection procedure afforded the desired 3,4-dihydroxyglutamic acids. 相似文献
72.
Katsutoshi Kubota Makoto Minakata Shoichi Saito Shingo Uehara 《Optical and Quantum Electronics》1978,10(3):205-210
A low drive-voltage optical modulator using a Ti-diffused UNbO3 optical waveguide has been fabricated. Stabilization against ambient temperature change was realized by using a miniature halfwave plate. The halfwave voltage, 3 dB bandwidth, optical insertion loss and extinction ratio were 3·8 V (at 1·06m wavelength), 850 MHz, 10 dB and 13 dB, respectively. A reduction scheme for the optical absorption caused by metallic electrodes, and an analysis of the modulator high frequency response are also reported. 相似文献
73.
A column-switching high-performance liquid chromatography (HPLC)-fluorescence detection method for the determination of three methylated arginines, N(G)-monomethyl-L-arginine (L-NMMA), N(G),N(G)-dimethyl-L-arginine (asymmetric dimethyl-L-arginine, ADMA), and N(G),N(G)'-dimethyl-L-arginine (symmetric dimethyl-L-arginine, SDMA), which are endogenous nitric oxide synthase inhibitors, was developed. After fluorescence derivatization of plasma samples with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), the samples were injected into the HPLC system. The NBD-derivatized methylated arginines were trapped on a cation exchange column with filter to remove proteins, separated within 42 min on a reversed-phase column, and detected at an emission wavelength of 530 nm with excitation at 470 nm. The detection limits were 10 fmol for L-NMMA and 20 fmol for ADMA and SDMA with a signal-to-noise ratio of 3. A good linearity for calibration curves for each methylated arginine was observed within the range of 50-5000 fmol using homoarginine as an internal standard. The proposed method was applied to the quantitative determination of L-NMMA, ADMA and SDMA in rat plasma. The concentrations of L-NMMA, ADMA and SDMA in rat plasma were 0.16 +/- 0.01, 0.73 +/- 0.02 and 0.41 +/- 0.05 micromol l(-1), respectively (n= 5). 相似文献
74.
Nano-sized phosphine and pyridine ligands having tetraphenylphenyl-, m-terphenyl-, poly(benzylether) moieties were synthesized. These ligands showed a remarkable effect on homogeneous transition
metal catalyzed reactions. Pd(II) complexes with tetraphenylphenyl substituted pyridine ligands show high catalytic activities
for oxidation of ketones suppressing Pd black formation and maintains the catalytic activity for a long time. Rh(I) complex
catalysts with m-terphenyl substituted phosphine ligands showed remarkable rate acceleration in the hydrosilylation of ketones. In addition,
several phosphinocalixarene ligands were synthesized and their coordination studies with Pd(II), Pt(II), Ru(II), Ir(I), and
Rh(I) metals were documented. Ir(I) and Rh(I) cationic complexes with a 1,3,5-triphosphinocalix[6]arene ligand showed dynamic
behavior with size-selective molecular recognition. 相似文献
75.
Diversity-oriented organic synthesis (DOS) is a key concept for construction of skeletally diverse small molecule libraries to discover drug-like small molecules. Here, we describe a DOS class to transform a complex 7-oxanorbornene skeleton, which is readily accessible by a tandem Ugi/Diels-Alder reaction, into two heterotricycle skeletons selectively by using tandem ROM/CM/RCM reaction. In the present study, the mode of cyclization is pre-encoded by building blocks used in the complexity-generating tandem Ugi/Diels-Alder reaction. Since variable alkenes can be used in the CM reaction, our approach can be extended to construct both skeleton- and appendage-diverse small molecule libraries. 相似文献
76.
2,2′-Dipyridyl-2-furancarbothiohydrazone (DPFTH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) can be quantitatively extracted with DPFTH in benzene from aqueous solution buffered to 3.0–8.0. The extracted species has absorption maxima at 440, 477, and 738 nm and obeyed Beer's law over the range 0–40 μg of iron in 10 ml at 738 nm. The molar absorptivity at this wave length is 1.17 × 104 liters mole?1 cm?1. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were pKa1 = 2.88 and pKa1 = 6.70 at 25 °C and μ = 0.1. 相似文献
77.
Kentaro Ageishi Takeshi Endo Makoto Okawara 《Journal of polymer science. Part A, Polymer chemistry》1981,19(5):1085-1090
The behavior of viologen polymer (P-V2+) as an electron transfer catalyst in the reaction of hydrogen generation was studied. In the photoirradiation system, which contains triethanolamine (TEA), Ru(bpy)3+3, and P-V2+, the amount of hydrogen evolution was less than methyl viologen (MV2+); P-V2+, however, was more effective in sodium dithionite as the electron donor and showed higher initial rates than MV2+. 相似文献
78.
Hiroshi Takeuchi Makoto Nakagawa Takayuki Saito Toru Egawa Kiyoshi Tanaka Shigehiro Konaka Toshiyuki Mitsuhashi 《International journal of quantum chemistry》1994,52(6):1339-1348
The energy spectra of free water molecules were measured at scattering angles 2θ ranging from 10.5° to 75.7°, using an angle-dispersive-type diffractometer and synchrotron radiation as an X-ray source. A silicon (111) monochrometer was used to obtain incident X-rays with the wavelengths of (1.543/n) Å (n = 1,3,4,5). Observed inelastic scattering peaks are clearly separated from eleastic ones at s values [s = (4π/λ) sin Å] larger than 8 Å?1. The increase of the separation with an increasing s value was consistent with the classical theory of the Compton shift. The total (elastic plus inelastic) intensities were obtained over a range of s = 0.74–5.0 Å?1. Experimental difference intensities Δσee and Δσne were obtained separately by combining the X-ray and high-energy electron scattering data. The experimental results are in reasonable agreement with the theoretical intensities calculated from SCF and CI molecular wave functions with a basis set of double-zeta plus polarization functions. © 1994 John Wiley & Sons, Inc. 相似文献
79.
Makoto Masuda Satoru Takamatu Noriyuki Nishimura Saburo Komatsubara Tetsuya Tosa 《Applied biochemistry and biotechnology》1993,43(3):189-197
Serratia marcescens SP511 was previously reported to be anl-proline-producing strain that harbors a recombinant plasmid carrying the mutant type of the proline operon. This strain produced 65 g/L ofl-proline in a medium containing 22% sucrose and urea after 5 d of incubation under the conventional culture conditions. We searched for more suitable culture conditions for more abundantl-proline production by SP511. To improve the supply of a nitrogen source to cells, ammonium was used instead of urea and fed to a culture under control of the pH of the medium. The concentrations of MgSO4 and K2HPO4 were increased, and in addition, sucrose was continuously added to the culture at a final concentration of 32%. Under these conditions, the cell amount was increased twofold over that under the previous conditions andl-proline production reached a maximum of more than 100 g/L after 4 d of incubation. 相似文献
80.
Shizuko Kobayashi Makoto Takehana Chiharu Tohyama 《Photochemistry and photobiology》1996,63(1):106-110
Abstract— The protective effect of administration of glutathione (GSH) isopropyl ester on photodamage, such as lipid peroxidation, inflammation and tumorigenesis induced by UV exposure (290–400 nm, max. 312 nm), was investigated using hairless mice. Pretreatment with 20 mg/kg GSH isopropyl ester prevented the increases of thiobarbituric acid-reactive substance (TBARS) formation in skin and serum sialic acid, indices of lipid peroxidation and inflammatory reaction, respectively, which were caused by a single dose (15 kj/m2 ) of UV irradiation. The level of epidermal GSH in skins of the GSH ester-treated mice was maintained within normal limits. When mice were exposed to UV at a dose of 2 kj/m2 , three times weekly, skin tumors developed in all of them after 25 weeks. The formation of skin tumors was significantly inhibited by administration of 10 mg/kg GSH ester prior to each UV irradiation for 25 weeks. Moreover, the increases of cutaneous TBARS and serum sialic acid in the tumor-bearing mice were also prevented by continuous pretreatment with GSH ester. Even after 24 weeks, the epidermal GSH content of the pretreated mice was mostly retained compared to nonirradiated mice. However, administration of GSH prior to acute or chronic UV irradiation had no effect on the UV-induced damage. The present results suggest that the protection from photo-damage afforded by pretreatment with GSH ester is due to maintenance of a normal GSH level. 相似文献