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71.
Seiki Saito Norio Bunya Masami Inaba Toshio Moriwake Sigeru Torii 《Tetrahedron letters》1985,26(43):5309-5312
Chiral β-hydroxy-α-amino acids such as erythro-β-hydroxy-L-aspartic acid and erythro-β-hydroxymethyl-L-serine derivatives have been synthesized in optically pure form from L- and D-tartaric acids through a novel oxirane ring-opening reaction and a selective reduction of α-hydroxy ester as key steps. 相似文献
72.
Huh KM Cho YW Chung H Kwon IC Jeong SY Ooya T Lee WK Sasaki S Yui N 《Macromolecular bioscience》2004,4(2):92-99
Supramolecular hydrogels have been prepared on the basis of polymer inclusion complex (PIC) formation between poly(ethylene glycol) (PEG)-modified chitosans and alpha-cyclodextrin (alpha-CD). A series of PEG-modified chitosans were synthesized by coupling reactions between chitosan and monocarboxylated PEG using water-soluble carbodiimide (EDC) as coupling agent. With simple mixing, the resultant supramolecular assembly of the polymers and alpha-CD molecules led to hydrogel formation in aqueous media. The supramolecular structure of the PIC hydrogels was confirmed by differential scanning calorimetry (DSC), X-ray diffraction, and (13)C cross-polarized/magic-angle spinning (CP/MAS) NMR characterization. The PEG side-chains on the chitosan backbones were found to form inclusion complexes (ICs) with alpha-CD molecules, resulting in the formation of channel-type crystalline micro-domains. The IC domains play an important role in holding together hydrated chitosan chains as physical junctions. The gelation property was affected by several factors including the PEG content in the polymers, the solution concentration, the mixing ratio of host and guest molecules, temperature, pH, etc. All the hydrogels in acidic conditions exhibited thermo-reversible gel-sol transitions under appropriate conditions of mixing ratio and PEG content in the mixing process. The transitions were induced by supramolecular association and dissociation. These supramolecular hydrogels were found to have phase-separated structures that consist of hydrophobic crystalline PIC domains, which were formed by the host-guest interaction between alpha-CD and PEG, and hydrated chitosan matrices below the pK(a).The formation of inclusion complexes between alpha-cyclodextrin and PEG-modified chitosan leads to the formation of hydrogels that can undergo thermo-reversible supramolecular dissociation. 相似文献
73.
An organodisulfide with a pair of adamantane moieties was synthesized, and its self-assembled monolayer (SAM) was formed on Au(111). The adamantane moieties are almost spherical and much bulkier than alkyl chains. The structure was characterized by scanning tunneling microscopy. Two-dimensional crystals of the SAM were found to be four orientationally different hexagonals with almost the same lattice constant with 4 radical 3a/3 and 7a/3 (a = 0.2884 nm, the Au lattice constant). The structure is assigned to four of the high-order commensurate adlayers. The present study of geometry and energetics for self-assembling of such an organosulfur compound with spherical cages provides a new insight into the probable SAM structure of various thiolate derivatives on Au(111). 相似文献
74.
Refractive indices of organo‐metallic and ‐metalloid compounds: A long‐range corrected DFT study
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Shintaro Maekawa Krzysztof Moorthi Yasuteru Shigeta 《Journal of computational chemistry》2016,37(32):2759-2769
Refractive indices of metal‐ and metalloid‐containing compounds are systematically evaluated using the Lorentz–Lorenz equation with polarizabilities obtained via density functional theory (DFT). Among exchange‐correlation functionals studied, the long‐range corrected (LC) fuctionals yield the lowest errors for the polarizabilities of gaseous compounds and refractive indices of liquids. The LC‐DFT predicts very well the wavelength dependence of refractive indices. A scheme for computing Abbe numbers of organometallic and organometaloid compounds is proposed and a refractive index – Abbe number plot for 80 compounds is constructed. The compounds containing heavier metals tend to have higher refractive index and lower Abbe number, but several outliers, among them Te(CH3)2, Ni(PF3)4, Sb(C2F3)3, Hg(C2F3)2, are found. For Hg(C2F3)2, also the effect of intramolecular and intermolecular degrees of freedom on polarizability is investigated. The absolute relative error in polarizability decreases from 5.7% for monomer model to 1.7% when a dimer model (derived from the available experimental crystal data) is employed. © 2016 Wiley Periodicals, Inc. 相似文献
75.
76.
Ryo Matsumoto Zhufeng Hou Shintaro Adachi Masanori Nagao Sayaka Yamamoto Peng Song 《高压研究》2020,40(1):22-34
ABSTRACTData-driven exploration for pressure-induced superconductors was performed based on the high-throughput first-principles screening of electronic band structures. In the screening conditions, we focused on the characteristics including a narrow band gap, flat band feature, and possibility of metallization under high pressure. The 27 promising compounds were screened out from the database of Atomwork for the candidates of new pressure-induced superconductors. Among the candidates, we actually synthesized three compounds in a single crystal, and all candidates exhibited the pressure-induced superconductivity. For the in-situ electrical transport measurements, we developed a novel configuration of diamond anvil cell with boron-doped diamond electrodes and an undoped diamond insulating layer. The discovered new pressure-induced superconductors via the data-driven approach and the developed diamond anvil cell were summarized in this paper. 相似文献
77.
Tatsuya Yanagisawa Hiroyuki Hidaka Hiroshi Amitsuka Shintaro Nakamura Satoshi Awaji Elizabeth L. Green 《哲学杂志》2020,100(10):1268-1281
ABSTRACTIn this study, ultrasonic measurements were performed on a single crystal of cubic PrNi2Cd20, down to a temperature of 0.02?K, to investigate the crystalline electric field ground state and search for possible phase transitions at low temperatures. The elastic constant (C11?C12)/2, which is related to the Γ3-symmetry quadrupolar response, exhibits the Curie-type softening at temperatures below ~30?K, which indicates that the present system has a Γ3 non-Kramers doublet ground state. A leveling-off of the elastic response appears below ~0.1?K toward the lowest temperatures, which implies the presence of level splitting owing to a long-range order in a finite-volume fraction associated with Γ3-symmetry multipoles. A magnetic field–temperature phase diagram of the present compound is constructed up to 28?T for H || [110]. A clear acoustic de Haas–van Alphen signal and a possible magnetic-field-induced phase transition at H ~26?T are also detected by high-magnetic-field measurements. 相似文献
78.
79.
Kaho Tanaka Naohiko Akasaka Tomoyuki Kosai Shunya Honda Yuya Ushijima Shintaro Ishida Takeaki Iwamoto 《Molecules (Basel, Switzerland)》2021,26(6)
π-Electron systems of silicon have attracted attention because of their narrow HOMO-LUMO gap and high reactivity, but the structural diversity remains limited. Herein, new dialkylboryl-substituted disilenes were synthesized by the selective desilylation-borylation of the corresponding trimethylsilyl-substituted disilenes. The dialkylboryl-substituted disilenes were fully characterized by a combination of NMR spectroscopy, MS spectrometry, single-crystal X-ray diffraction analysis, and theoretical calculations. The longest-wavelength absorption bands of boryldisilenes were bathochromically shifted compared to the corresponding silyl-substituted disilenes, indicating a substantial conjugation between π(Si=Si) and vacant 2p(B) orbitals. In the presence of 4-(dimethylamino)pyridine (DMAP), the dialkylboryl groups in the boryl-substituted disilenes were easily converted to trimethylsilyl groups, suggesting the dialkylboryl-substituted disilenes in the presence of a base serve as the surrogates of disilenyl anions (disilenides). 相似文献
80.
Asuka Nishikawa Shintaro Saito Yuichi Hashimoto Kenji Koga Ryuichi Shirai 《Tetrahedron letters》2001,42(52)
Efficient synthesis of l-α-phosphatidyl-d-myo-inositol 3,5-bisphosphate was achieved from 1,2,5,6-diisopropylidene-d-glucose by utilizing ring-closing metathesis and catalytic OsO4 dihydroxylation. 相似文献