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571.
Shiina I Takasuna YJ Suzuki RS Oshiumi H Komiyama Y Hitomi S Fukui H 《Organic letters》2006,8(23):5279-5282
[Structure: see text] The total synthesis of pseudo 2-epibotcinolide (1b) through several featured synthetic approaches has been attained. First, the chiral linear precursors of the nine-membered ring compound is stereoselectively constructed by the asymmetric aldol reaction for producing beta-hydroxy ester units. Second, the key cyclization reaction to form the nine-membered lactone moiety is efficiently achieved by the extremely facile and powerful mixed-anhydride method promoted by 2-methyl-6-nitrobenzoic anhydride (MNBA) with basic promoters. 相似文献
572.
Kitagawa F Kamiya M Okamoto Y Taji H Onoue S Tsuda Y Otsuka K 《Analytical and bioanalytical chemistry》2006,386(3):594-601
The applicability of three-layer coatings consisting of three different polymers (A+-B−-C+ coating) prepared by a successive multiple ionic-polymer layer (SMIL) coating technique to the immobilization of polypeptides
and/or proteins onto the inner surface of the capillaries was investigated to provide a high-performance separation medium
for proteins and enantiomers in capillary electrophoresis (CE). To obtain a stable protein-coated capillary, high molecular
mass poly(ethyleneimine) (PEI) was employed as the first layer in the A+-B−-C+ coating, and then a cationic protein was immobilized as the third layer. Comparisons of analytical performances between the
A+-B−-C+ coating and the conventional SMIL-coated (A+-B−-A+ coating) capillary were conducted. The CE separation of cationic proteins was successfully achieved with the prepared capillaries.
In addition, the polypeptide- and protein-coated capillaries were applied to the chiral separation of a binaphthyl compound.
It should be noted that the chiral separation efficiency was strongly dependent on the second anionic polymer layer of the
coating. Effects of the interaction between oppositely charged ionic polymer layers on the separation efficiency are discussed. 相似文献
573.
574.
We have prepared a new layered oxycarbide, [Al5.25(5)Si0.75(5)][O1.60(7)C3.40(7)], by isothermal heating of (Al4.4Si0.6)(O1.0C3.0) at 2273 K near the carbon-carbon monoxide buffer. The crystal structure was characterized using X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX). The title compound is trigonal with space group R3?m (centrosymmetric), Z=3, and hexagonal cell dimensions a=0.32464(2) nm, c=4.00527(14) nm and V=0.36556(3) nm3. The atom ratios Al:Si were determined by EDX, and the initial structural model was derived by the direct methods. The final structural model showed the positional disordering of one of the three types of Al/Si sites. The reliability indices were Rwp=4.45% (S=1.30), Rp=3.48%, RB=2.27% and RF=1.25%. The crystal is composed of three types of domains with nearly the same fraction, one of which has the crystal structure of space group R3¯m. The crystal structure of the remaining two domains, which are related by pseudo-symmetry inversion, is noncentrosymmetric with space group R3m. 相似文献
575.
Ken Tanaka Yayoi Sawada Yusuke Aida Maliny Thammathevo Rie Tanaka Hiromi Sagae Yousuke Otake 《Tetrahedron》2010,66(8):1563-3187
Convenient as well as convergent synthesis of functionalized tetrahydronaphthalenes has been accomplished under mild reaction conditions by the cationic rhodium(I)/H8-BINAP complex-catalyzed [2+2+2] cycloaddition of 1,7-octadiyne derivatives with functionalized monoynes. The effect of the diyne tether lengths was investigated, which revealed that 1,6-heptadiyne and 1,7-octadiyne exhibit higher reactivity than 1,8-nonadiyne. Mechanistic studies indicated that the present rhodium-catalyzed [2+2+2] cycloaddition proceeds through the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne with rhodium. On the other hand, in the reactions of diynes and dimethyl acetylenedicarboxylate, the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne and a monoyne with rhodium would also be involved. 相似文献
576.
Tada S Inaba C Mizukami K Fujishita S Gemmei-Ide M Kitano H Mochizuki A Tanaka M Matsunaga T 《Macromolecular bioscience》2009,9(1):63-70
The resistance of random copolymers of BMA and CMB against biofouling was evaluated. The amount of proteins adsorbed onto the CMB copolymers was smaller than that onto other polymers (non-ionic polymers and copolymers of ordinary ionic monomers and BMA) and decreased with an increase in the content of CMB residues. Furthermore, there was a dramatic decrease in the number of cells (platelets and fibroblasts) that adhered to the CMB copolymers compared with that to other polymers. In contrast with this, CMB copolymers were slightly perturbative to both complement and coagulation systems. However, the overall results suggest that zwitterionic moieties are effective for making polymer materials biocompatible due to their excellent anti-biofouling property. 相似文献
577.
Hiromi Kaneko Atsushi Hosaka Olaf Scholten 《The European Physical Journal A - Hadrons and Nuclei》2012,48(5):56
We study the photoproduction of r \rho -mesons in a model of hidden local symmetry. For this purpose, the r \rho -meson is introduced as a hidden-gauge boson in a non-linear sigma model. For charged r \rho -meson photoproduction, the model takes into account the r \rho -meson magnetic moments from the three-point vertex in the kinetic terms. We show that the magnetic interaction of the charged
r \rho -meson has a significant effect on the total cross-sections through the r \rho -meson exchange process, which is proportional to the energy of the photon. The t -channel dominance may be used for the study of structures of various unstable particles. 相似文献
578.
Ahmed Ashour Ahmed Elbermawi Yhiya Amen Ahmed E. Allam Hiromi Ikeda Maki Nagata Kenta Kumagae Tomoyo Azuma Aya Taguchi Takuya Takemoto Masako Matsumoto Kuniyoshi Shimizu 《Molecules (Basel, Switzerland)》2023,28(1)
This study targets the evaluation of melanin synthesis inhibition activity of the bamboo shoot skin as agro-waste. The total methanolic extract of bamboo peel extract was evaluated for its skin protective effects via measuring its melanin inhibitory activity and its suppression activity on the expression of tyrosinase mRNA levels. Results showed that bamboo peel extract has a good ability for the inhibition of melanin synthesis so further studies were performed for the isolation of its constituents. Twelve compounds have been isolated from the shoot skin of Phyllostachys pubescens. Their structures were elucidated based on extensive spectroscopic methods. The melanin inhibition potential of the isolates was tested with their collagen-production-promoting activity for the determination of active principles. Results showed that Betulinic acid, tachioside, and 1,2-dilinolenin significantly suppressed melanin production per cell compared to control. Triacontanol, tricin, and (+)-lyoniresinol 9′-O-glucoside also tended to decrease melanin production per cell. These findings indicated that the skin of bamboo shoots, a significant agricultural waste, is a useful natural source for further research on its potential for aging problems such hyperpigmentation and cognitive function impairment. 相似文献
579.
Reversible oxygen-binding was observed at low temperature for the poly(vinylimidazole-co-octyl methacrylate) complexes of the simple or planar cobaltporphyrins (CoP) such as cobalt-tetraphenylporphyrin and cobalt-octaethylporphyrin. The oxygen-binding affinity and rate constants were compared with those for the cobalt-picketfence porphyrin, a typical oxygen-carrier. The low oxygen-binding affinity for the CoP complexes was attributed to the enormously large oxygen-releasing rate constant. 相似文献