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101.
Nagamitsu T Takano D Marumoto K Fukuda T Furuya K Otoguro K Takeda K Kuwajima I Harigaya Y Omura S 《The Journal of organic chemistry》2007,72(8):2744-2756
The total synthesis of borrelidin has been achieved. The best feature of our synthetic route is macrocyclization at C11-C12 for the construction of an 18-membered ring after esterification between two segments. A detailed examination of the macrocyclization led us to the samarium(II) iodide-mediated intramolecular Reformatsky-type reaction as the most efficient synthetic approach. The two key segments were synthesized through regioselective methylation, directed hydrogenation, stereoselective Reformatsky-type reaction, and MgBr2.Et2O-mediated chelation-controlled allylation. 相似文献
102.
Park JS Akiyama Y Yamasaki Y Kataoka K 《Langmuir : the ACS journal of surfaces and colloids》2007,23(1):138-146
Novel thermosensitive polyion complex (PIC) micelles were prepared in an aqueous medium based on the complexation of a pair of oppositely charged block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(amino acid)s (PiPrOx-b-PAA), containing thermosensitive PiPrOx segments. The controlled synthesis of PiPrOx-b-PAA was achieved via the ring-opening anionic polymerization of N-carboxyanhydrides (NCA) of either eta-benzyloxycarbonyl-l-lysine (Lys(Z)-NCA) or beta-benzyl-l-aspartate (BLA-NCA) with omega-amino-functionalized PiPrOx macroinitiators and the subsequent deprotection reaction under acidic or basic conditions. Gel permeation chromatography (GPC) and 1H NMR spectroscopy revealed that the syntheses of two block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(l-lysine) [PiPrOx-P(Lys)] and poly(2-isopropyl-2-oxazoline)-b-poly(aspartic acid) [PiPrOx-P(Asp)], proceeded almost quantitatively to give samples with a narrow molecular weight distribution (Mw/Mn = 1.2). The mixing of these two oppositely charged block ionomers in an aqueous medium led to the spontaneous formation of PIC micelles, which was confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The PIC micelles were spherical particles with a narrow distribution in the range of the measured concentration (0.125-1 mg/mL) and were stable without any secondary aggregates. Furthermore, the PIC micelles had a constant cloud-point temperature (Tcp) of approximately 32 degrees C under physiological conditions regardless of the total concentration, suggesting that the concentration factor is almost negligible with respect to the Tcp of the micelles presumably because of the increased local concentration of the PiPrOx segments in the shell layer. These PIC micelles have a promising application as a size-regulated smart nanocontainer loading charged compounds as well as bearing a thermosensitive outer shell that is useful for physical affinity control. 相似文献
103.
H. Oda M. Akiyama T. Masuda T. Nakamura 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(2):439-442
We measured radiocarbon age of an ancient document “Minamoto no Yoritomo Sodehan Migyosho”. The content tells that it was
issued in 1189 by “Minamoto no Yoritomo” known as the virtually first shogun in Japan to grant “Matsugi” family the privilege
of controlling craftsmen of foundry industry. Paleographical views, however, suggested that it can be a counterfeit. The radiocarbon
dating clarified that the document was written not in the 12th but after the 16th century. 相似文献
104.
A convergent synthesis of the key synthetic intermediate of hemibrevetoxin B was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis. 相似文献
105.
Fujitani T Nakamura I Kobayashi Y Takahashi A Haneda M Hamada H 《The journal of physical chemistry. B》2005,109(37):17603-17607
Adsorption and reactions of NO on clean and CO-precovered Ir(111) were investigated by means of X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HR-EELS), infrared reflection absorption spectroscopy (IRAS), and temperature-programmed desorption (TPD). Two NO adsorption states, indicative of fcc-hollow sites and atop sites, were present on the Ir(111) surface at saturation coverage. NO adsorbed on hollow sites dissociated to Na and Oa at temperatures above 283 K. The dissociated Na desorbed to form N2 by recombination of Na at 574 K and by a disproportionation reaction between atop-NO and Na at 471 K. Preadsorbed CO inhibited the adsorption of NO on atop sites, whereas adsorption on hollow sites was not affected by the coexistence of CO. The adsorbed CO reacted with dissociated Oa and desorbed as CO2 at 574 K. 相似文献
106.
A biosynthetic gene cluster containing five genes, alt1-5, was cloned from Alternaria solani, a causal fungus of early blight disease to tomato and potato. Homology searching indicated that the alt1, 2, and 3 genes code for cytochrome P450s and the alt4 gene for a FAD-dependent oxygenase/oxidase. The alt5 gene encodes a polyketide synthase (PKS), named PKSN, that was found to be an iterative type I complex reduced-type PKS with a C-methyltransferase domain. To identify the PKSN function, the alt5 gene was introduced into the fungal host Aspergillus oryzae under an alpha-amylase promoter. The transformant produced a polyketide compound, named alternapyrone, whose structure is shown to be 3,5-dimethyl-4-hydroxy-6-(1,3,5,7,11,13-hexamethyl-3,5,11-pentadecatrienyl)-pyran-2-one. Labeling experiments confirmed that alternapyrone is a decaketide with octa-methylation from methionine on every C(2) unit except the third unit. 相似文献
107.
Adsorption of NO on Pt(110)-(1 x 2) and (1 x 1) surfaces has been investigated by density functional theory (DFT) method (periodic DMol(3)) with full geometry optimization and without symmetry restriction. Adsorption energies, structures, and N-O stretching vibrational frequencies of NO are studied by considering multiple possible adsorption sites and comparing with the experimental data. Adsorption is strongly dependent on both coverage and surface phase. The assignment of adsorption sites has been carried out with precise calculation of vibrational frequencies for NO on various sites. We clearly show the NO site switching on both of the surfaces as found in the experiments: at low coverages, bridge species is formed on the surface, and at high coverages, NO switches to atop sites. 相似文献
108.
109.
Jun-ichi Yamada Maki Watanabe Hiroyuki Anzai Hiroyuki Nishikawa Isao Ikemoto Koichi Kikuchi 《Angewandte Chemie (International ed. in English)》1999,38(6):810-813
Metallic behavior down to low temperature is shown by charge transfer salts of BDH-TTP ( 1 ), a structural isomer of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF). In the case of (BDH-TTP)2PF6 this behavior is attributed to the structure, which is made up of κ-type sheets of BDH-TTP donor molecules and sheets of PF6− anions. 相似文献
110.
Kobayashi S Miyamura H Akiyama R Ishida T 《Journal of the American Chemical Society》2005,127(25):9251-9254
A novel, highly active immobilized ruthenium catalyst, which can be successfully used in oxidation of alcohols to aldehydes and ketones, has been developed. In contrast to most immobilized catalysts, the Ru catalyst has activity that is higher than that of the original non-immobilized catalyst. In a batch system, the Ru catalyst was recovered and reused several times without loss of activity. The catalyst was also applied to a flow system, in which excellent conversions and yields were demonstrated. No leaching of Ru was observed in both cases. 相似文献