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171.
Akinobu Matsuzawa Dr. Christopher R. Opie Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):68-71
An enantioselective total synthesis of thuggacin B, a natural product exhibiting antibiotic activity against Mycobacterium tuberculosis, is described. Asymmetric direct aldol reactions promoted by Cu and Zn catalysts play a pivotal role in constructing four stereogenic centers. The use of direct aldol reactions as the initial steps for the synthesis of two key fragments allowed the construction of the other stereogenic centers through chirality transfer. 相似文献
172.
E. Otsuka K. Kurumada A. Suzuki S. Matsuzawa K. Takeuchi 《Journal of Sol-Gel Science and Technology》2008,46(1):71-78
Mesoporous bulk silica with optical transparency and high porosity can be prepared using a gel-templating method. This unique
material has potentially wide-ranging applications as containers of specific molecules, smart deliverers of target molecules,
and photonic devices. Among the potential applications, the use of silica as a photocatalyst is explored in this paper; the
photocatalyst was prepared by loading titanium dioxide (titania) from the titania precursor solution into the mesoporous structure
of silica with a controlled pore size. Even after crystallization, the titania-loaded silica remained highly mesoporous with
uniform pore size and optical transparency. The ability of the adsorption and decomposition of acetaldehyde gas was evaluated
by measuring the concentration change of the gas with and without the irradiation of ultraviolet rays. As a result, the specific
surface area, the amount of titania and the calcination temperature were essential in determining the adsorption ability as
well as the decomposition ability. 相似文献
173.
The geometric and electronic structures of the ground and low-lying states for the Al(12)Cs(-), Al(11)Cs(2) (-), and Al(10)Cs(3) (-) clusters were examined using the density functional theory. Semi-icosahedral structures of the Al(12)Cs(-) and Al(11)Cs(2) (-) clusters were found as the ground state. The most stable structure of the Al(10)Cs(3) (-) cluster is a distorted icosahedron structure. The vertical detachment energy of these clusters and the anion photoelectron spectra (PES) were compared. The peaks of the anion PES were assigned on the basis of the shell model. The single peak of 3.1-3.2 or 2.5-2.7 eV for the Al(12)Cs(-) or Al(11)Cs(2) (-) cluster, respectively, is observed due to the electron detachment from the 2p or 1f or 1f+2p shells. Two large peaks of 2.1 eV and 3.1-3.3 eV correspond to the electron detachments from the 1f+2p and 2p, and 1d+1f shells, respectively. It was found that a second peak appears with the hybridization of the 1d and 1f shells due to the distortion from the icosahedral structure in the Al(10)Cs(3) (-) cluster. 相似文献
174.
1,1-Disubstituted 3-aryl-2-propyn-1-ols undergo regio- and stereoselective cross-coupling on treatment with bis(trimethylsilyl)acetylene in the presence of a rhodium catalyst via cleavage of C(sp)-C(sp3) and C(sp)-Si bonds to produce the corresponding 2-hydroxymethyl-(E)-enynes. The subsequent desilylative Sonogashira coupling followed by base-promoted cyclization affords fluorescent dihydrofuran derivatives. 相似文献
175.
Akinobu Matsuzawa Akihiro Nojiri Naoya Kumagai Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(17):5036-5042
Solvent‐dependent, self‐discrimination of diamides is described. Mixing a solution of (R)‐ 1 a and (S)‐ 1 a , which are valine‐derived, bis(2‐hydroxyphenyl)diamide‐bearing, multiple hydrogen‐bonding modules, in dichloromethane immediately led to the formation of a thick suspension comprising a 1:1 heterochiral aggregate of 1 a . The solubility of heterochiral 1 a was substantially lower in halogenated solvents than in ethyl acetate. A perusal of racemic crystal structures obtained from chloroform and ethyl acetate revealed a significant difference in the crystal‐packing pattern, which is likely to be the basis for the pronounced difference in solubility. Specific self‐discrimination of 1 a in an ensemble of eight structurally related molecules showcased the specific aggregation through the hydrogen‐bonding network of the bis(2‐hydroxyphenyl)diamide framework. The low solubility of heterochiral 1 a in halogenated solvent was exploited to achieve high stereoselectivity in a catalytic asymmetric reaction by using a low enantiomeric excess sample of 1 a . 相似文献
176.
Masahiro Isaka Hiroaki Homma Masaaki Kimura Akinobu Dote Akira Ohnishi 《Few-Body Systems》2013,54(1-4):395-398
The deformation change of ${^{9}_\Lambda}$ Be and the low-lying states of ${^{12}_{\Lambda}}$ Be are studied by using the antisymmetrized molecular dynamics for hypernuclei (HyperAMD). In ${^{9}_{\Lambda}}$ Be, the Λ hyperon in p orbit enhances nuclear quadrupole deformation, while the Λ hyperon in s orbit reduces it. In ${^{12}_{\Lambda}}$ Be, the ground state parity inverted in 11Be is reverted in ${^{12}_{\Lambda}}$ Be by adding a Λ hyperon as an impurity (impurity effect). 相似文献
177.
The 11B NMR spectra of p-carboxybenzeneboronic acid (PCBA) ions demonstrated that their chemical shifts depend on the pH. At a lower pH, PCBA exists as a mixture of neutral PCBA and the monoanion with a trigonal structure, and at higher pH as the dianion with a tetrahedral structure. In the intermediate pH region, both the mono- and dianion coexist. The pKa of the monoanion of PCBA has been estimated to be 8.53. The complex formation constants of PCBA with several monosaccharides suggest that PCBA-fructose complex is most predominant. 相似文献
178.
179.
Kaoru Yamanouchi Takahiro Matsuzawa Kozo Kuchitsu Yoshiaki Hamada Masamichi Tsuboi 《Journal of Molecular Structure》1985
The quadratic force constants of the five possible conformers of allylamine were calculated by an ab initio MC method. The infrared spectra of this molecule in the gas phase were remeasured and analyzed on the basis of the calculated vibrational frequencies. A potential energy surface with respect to the skeletal torsions was also calculated. The relative abundances of the S+G+, ST, CT, CG, and S+G? conformers, predicted to be 44:32:16:7:1 at room temperature, are consistent with the experimental data. 相似文献
180.