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61.
Hiroko Nakagawa Kumiko Ohtsuka Katsuhito Sugahara Chika Kobayashi Yuichi Masuoka Koh-ichi Yamada Masami Kawase 《Tetrahedron: Asymmetry》2010,21(6):659-664
Helical [5]thiaheterohelicene 5HM, which rapidly interconverts between P and M enantiomers in solution, was connected to helical l-phenylalanine oligomers with an ester linkage to give peptidehelicenes (5Fn, where n: number of bonded phenylalanines). The characteristics of 5F4 and 5F5 with two types of helixes in a molecule were investigated, particularly in comparison with those of 5F1–5F3 with an incomplete coil of a peptide moiety. l-Phenylalanine peptide chains induced a shift in the equilibrium between the P and M helixes of 5HM toward the P side for all the 5Fns examined. The enantiomeric excess (ee) of the P form increased with a decrease in temperature, together with an elongation of the peptide chains. 5F4 and 5F5 in hot solutions of some solvents formed a gel at room temperature, whereas 5F1–5F3 showed no such behavior. In this gel, the stable helical form of the 5HM moiety in 5F4 and 5F5 was observed to be the M form in contrast to that in their solutions. 相似文献
62.
A diketone precursor of air-stable bis-2-thienyl-2,6-anthracene was prepared and quantitatively converted to the target acene by photoirradiation of the n-π∗ absorption both in solution and as a film, in air. 相似文献
63.
Tetrabenzoperipentacene: Stable Five‐Electron Donating Ability and a Discrete Triple‐Layered β‐Graphite Form in the Solid State
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Akinobu Matsumoto Dr. Mitsuharu Suzuki Dr. Daiki Kuzuhara Dr. Hironobu Hayashi Prof. Dr. Naoki Aratani Prof. Dr. Hiroko Yamada 《Angewandte Chemie (International ed. in English)》2015,54(28):8175-8178
An oxidative ring‐closure reaction of a tetranaphthylpyrene derivative led to the synthesis of a 56 all‐carbon conjugated tetrabenzoperipentacene. In the single‐crystal X‐ray structure, three molecules make a triple‐layered cluster by π‐stacking, wherein each layer rotates by 120°, and is thus considered a petit β‐graphite. As for the optical properties, the Stokes shift is extremely small (10 cm?1), thus indicating its remarkably rigid framework. The tetrabenzoperipentacene exhibits reversible five‐electron oxidation waves in cyclic voltammetry, and is regarded as a counterpart to the fullerene C60 in terms of stable multicharge‐storage nanocarbon materials. 相似文献
64.
Ye Ji Kim Sun Min Kim Eun Jin Cho Hideo Hosono Jung Woon Yang Sung Wng Kim 《Chemical science》2015,6(6):3577-3581
A simple and highly efficient transfer hydrogenation of alkynes and alkenes by using a two-dimensional electride, dicalcium nitride ([Ca2N]+·e–), as an electron transfer agent is disclosed. Excellent yields in the transformation are attributed to the remarkable electron transfer efficiency in the electride-mediated reactions. It is clarified that an effective discharge of electrons from the [Ca2N]+·e– electride in alcoholic solvents is achieved by the decomposition of the electride via alcoholysis and the generation of ammonia and Ca(OiPr)2. We found that the choice of solvent was crucial for enhancing the electron transfer efficiency, and a maximum efficiency of 80% was achieved by using a DMF mixed isopropanol co-solvent system. This is the highest value reported to date among single electron transfer agents in the reduction of C–C multiple bonds. The observed reactivity and efficiency establish that electrides with a high density of anionic electrons can readily participate in the reduction of organic functional groups. 相似文献
65.
Hiroshi Mizoguchi SangWon Park Haruhiro Hiraka Kazutaka Ikeda Toshiya Otomo Hideo Hosono 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(10):2975-2978
Using a high pressure technique and the strong donating nature of H−, a new series of tetragonal La2Fe2Se2O3‐type layered mixed‐anion arsenides, Ln2M2As2Hx, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M2H square net, which has anti CuO2 square net structures accompanying two As3− ions, is sandwiched by (LaH)2 fluorite layers. Notably, strong metal–metal bonding with a distance of 2.80 Å was confirmed in La2Ti2As2H2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt‐like ionic hydrides and transition‐metal hydrides with metallic characters. 相似文献
66.
Pyranosides with 2,3-trans carbamate or 2,3-trans carbonate groups are anomerized under mild acidic conditions via endocyclic cleavage reaction. In order to understand the nature of the anomerization reaction via the endocyclic cleavage-recyclization process, the substituent effects at various positions were investigated. 相似文献
67.
Sato T Yoshida S Hoshino H Tanno M Nakajima M Hoshino T 《Journal of the American Chemical Society》2011,133(25):9734-9737
In this study, mono- and pentacyclic C(35) terpenes from Bacillus subtilis were biosynthesized via the cyclization of C(35) isoprenoid using purified enzymes, including the first identified new terpene cyclase that shows no sequence homology to any of the known terpene cyclases. On the basis of these findings, we propose that these C(35) terpenes should be called the new family of "sesquarterpenes." 相似文献
68.
Saito K Hosono K Kitazawa N Iwasaki Y Ito R Nakazawa H 《Journal of AOAC International》2011,94(3):923-930
A quality assessment method for commercially available, optically active flavor compounds, namely, menthol, menthyl acetate, borneol, perillaldehyde, and 1,8-cineol, was developed. A gas chromatograph equipped with a flame ionization detector and a DB-5ms capillary column was used for the chemical purity test. A GC/MS with a beta-DEX cyclodextrin column was used for the optical purity test, by which the enantiomeric separation of each flavor compound was achieved. Enantiomeric excess was calculated as an expression of optical purity. Of the 25 standard samples subjected to the chemical purity test, six were found to have lower purity than the data provided by the manufacturers. When the same samples were subjected to the optical purity test, 11 were found to have lower purity than that indicated on the reagent labels. These results suggest that there is a need to conduct an optical purity test, in addition to a chemical purity test, for the quality assessment of flavor standards. 相似文献
69.
Cyano-bridged bimetal assemblies demonstrate novel magnetic functionalities, particularly Prussian blue analogs, which have unique properties. In this perspective, we describe a charge-transfer phase transition, reversible photomagnetism, second harmonic generation and magnetization-induced second harmonic generation, ferroelectric ferromagnetism, humidity-sensitive magnetism, high ionic conductivity, and a coupling effect (which we named spin-ionics) between ionic conduction and magnetic ordering with Prussian blue analogs. 相似文献
70.
Morohashi N Noji S Nakayama H Kudo Y Tanaka S Kabuto C Hattori T 《Organic letters》2011,13(13):3292-3295
Powdery crystals of p-tert-butylthiacalix[4]arene (2) selectively include EtOH from 1:1 mixtures of MeOH-EtOH and EtOH-PrOH, and EtCO(2)H from HCO(2)H-EtCO(2)H. On the other hand, no acid is included from HCO(2)H-MeCO(2)H, even though MeCO(2)H is included from the neat acid. The origins of these phenomena are discussed based on X-ray analysis of inclusion crystals prepared separately by crystallization. 相似文献