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41.
Hashizume M Nagasawa Y Suzuki T Kawashima S Kamitakahara M 《Colloids and surfaces. B, Biointerfaces》2011,84(2):545-549
Preparation of colloidal hydroxyapatite (HAp) particles under body fluid conditions was investigated with focusing on the effect of preparative conditions on crystallinity of the resulting particles. Tris(hydroxymethyl)aminomethane was added to 1.5SBF (a solution having 1.5 times higher ion concentrations than those of a simulated body fluid, SBF) to increase the solution pH, which resulted in induction of homogeneous nucleation of HAp in the solution. Colloidal HAp particles having diameters about 300 nm were obtained. When the reaction was proceeded at 70°C and the sample was dried by heating, it was effective to obtain HAp particles having high crystallinity. Experimental results support that remaining water in the sample contributed to increase HAp crystallinity. 相似文献
42.
Doi T Shibata K Yoshida M Takagi M Tera M Nagasawa K Shin-ya K Takahashi T 《Organic & biomolecular chemistry》2011,9(2):387-393
Total synthesis of the (S)-stereoisomer of telomestatin (1) was accomplished. (S)-Telomestatin exhibited potency four times that of the natural product, (R)-telomestatin, which was the most potent telomerase inhibitor previously reported. In the circular dichroism spectral analysis of the complexes possessing randomly structured single-stranded d[TTAGGG](4) oligonucleotide, (S)-telomestatin, like (R)-telomestatin, induced an antiparallel G-quadruplex structure. The melting temperature (T(m)) value of the (S)-isomer complex was greater than that of the (R)-telomestatin complex. Therefore, it is concluded that the stereochemistry of the thiazoline of telomestatin is important to the binding ability of a G-quadruplex binder, and (S)-telomestatin as a G-quadruplex binder is more potent than the natural product. 相似文献
43.
A concise enantioselective total synthesis of 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA), an extremely potent anti-HIV agent, has been accomplished from (R)-glyceraldehyde acetonide in 18% overall yield by a 12-step sequence involving a highly diastereoselective ethynylation of an α-alkoxy ketone intermediate. 相似文献
44.
Hayashi M Sasano Y Nagasawa S Shibuya M Iwabuchi Y 《Chemical & pharmaceutical bulletin》2011,59(12):1570-1573
A highly active organocatalyst for alcohol oxidation has been developed. 9-Azanoradamantane N-oxyl (Nor-AZADO 4), constituting an unhindered, stable nitroxyl radical, exhibits superior catalytic activity to 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and AZADOs in the oxidation of alcohols to their corresponding carbonyl compounds. 相似文献
45.
Dr. Yoshihiro Sohtome Bongki Shin Natsuko Horitsugi Prof. Dr. Keiichi Noguchi Prof. Dr. Kazuo Nagasawa 《化学:亚洲杂志》2011,6(9):2463-2470
Herein, we present details of our conformationally flexible, 1,3‐diamine‐tethered guanidine/bisthiourea organocatalysts for chemo‐, regio‐, and enantioselective 1,4‐type Friedel–Crafts reactions of phenols. These organocatalysts show a unique stereo‐discrimination governed by the differential activation entropy (ΔΔS≠), rather than by the differential activation enthalpy (ΔΔH≠). Extensive kinetic analyses using Eyring plots for a series of guanidine/bisthiourea organocatalysts revealed the key structural motif in the catalysts associated with a large magnitude of differential activation entropy (ΔΔS≠). A plausible guanidine–thiourea cooperative mechanism for the enantioselective Friedel–Crafts reaction is proposed. 相似文献
46.
Yoshikatsu Miyashita Tohru Okuyama Kazutomo Yamaura Kiyokatsu Jinno Shin-Ichi Sasaki 《Analytica chimica acta》1987
The carcinogenicities of polynuclear aromatic hydrocarbons in particulates extracted from diesel engine exhaust are predicted on the basis of the combined bay-L region theory proposed earlier, in conjunction with pattern recognition techniques. The predicted carcinogenicities agree well with experimental data, thus showing the validity of the proposed model equations. 相似文献
47.
Bungo Ochiai Jun‐ichi Nakayama Masayuki Mashiko Yoshiro Kaneko Tomomi Nagasawa Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5899-5905
This article describes the polyaddition of bifunctional five‐membered cyclic carbonates and diethylenetriamine. The polyaddition proceeded via the selective addition of the primary amino group to the cyclic carbonates to give poly(hydroxyurethane)s bearing a secondary amine structure in the main chain. The resulting poly (hydroxyurethane) having a secondary amine structure was crosslinked by a reaction with a bifunctional dithiocarbonate to give a networked poly(hydroxyurethane–mercaptothiourethane). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5899–5905, 2005 相似文献
48.
Hiroyuki Sasaki Akinori Tanaka Tazumi Nagasawa Shoji Suzuki Toshiro Nagase 《Solid State Communications》2004,129(2):91-95
We have carried out an angle-resolved photoemission study for CoSi2 nanofilms grown on the Si(111)-7×7 substrates. The surface of CoSi2(111) nanofilm changes from the bulk-truncated surface to the surface with additional Si-bilayer by annealing at higher temperature above 825 K. The angle-resolved photoemission spectra of the CoSi2 nanofilm annealed at 853 K show the spectral features originated from the surface resonance state on the CoSi2 surface terminated by Si-bilayer. From the detailed photoemission study, we discuss the surface electronic structure in CoSi2(111) nanofilms grown on Si(111) substrates. 相似文献
49.
50.
The efficiency of oxygen transfer from the transannular ozonide 1 to several organic substrates was investigated. The efficiency was estimated to be as high as 90% in the case of Ph3P as the substrate. 相似文献