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61.
The generation of Ni(PPh3)4 by electrochemical reduction was carried out in a divided cell containing NiCl2(PPh3)4, PPh3 and n-Bu4NBr in DMF with a lead plate as cathode and a platinum plate as anode under the stream of argon at 60°. Using this Ni(PPh3)4, biphenyls and the heterocyclic compounds were synthesized in fairly good yields. 相似文献
62.
Asymptotic distributions of the latent roots of the covariance matrix with multiple population roots
Yasuko Chikuse 《Journal of multivariate analysis》1976,6(2):237-249
An asymptotic expansion for large sample size n is derived by a partial differential equation method, up to and including the term of order n?2, for the 0F0 function with two argument matrices which arise in the joint density function of the latent roots of the covariance matrix, when some of the population latent roots are multiple. Then we derive asymptotic expansions for the joint and marginal distributions of the sample roots in the case of one multiple root. 相似文献
63.
64.
Sugiura H Nigorikawa Y Saiki Y Nakamura K Yamaguchi M 《Journal of the American Chemical Society》2004,126(45):14858-14864
Optically active acyclic ethynylhelicene oligomers were synthesized in high yields by a two-directional method involving Sonogashira coupling and deprotection. Their CD spectra in chloroform exhibited large differences between the oligomers with less than seven helicenes and their higher homologues, which indicated the formation of helical structures for the latter and random coil structures for the former. The helical heptamer gradually unfolded to a random coil structure in chloroform at room temperature. The unfolding rate was examined by CD in several aromatic solvents as well, and the rate constant k was found to be highly dependent on the type of aromatic substituent: k differed by seven orders of magnitude between iodobenzene and trifluoromethylbenzene. Several features of the rates are notable: The reaction rates in halobenzenes were in the order of iodobenzene > bromobenzene > chlorobenzene > benzene > fluorobenzene > m-difluorobenzene, those in alkylbenzenes were styrene > phenylacetylene > ethylbenzene > toluene > benzene, and those in heteroatom-substituted arenes were thioanisole > benzonitrile > anisole > ethyl benzoate > benzene > trifluoromethylbenzene. The log k values exhibited good correlation with the absolute hardness, eta, of the arenes, and higher unfolding rates were observed in the soft arenes. Vapor pressure osmometry studies indicated that the helical structure of the heptamer is dimeric in benzene, fluorobenzene, and trifluoromethylbenzene, while the random coil structure of the heptamer is monomeric in chloroform and toluene. When a chloroform solution of the random coil structure was concentrated to a small volume, the helical structure could be regenerated. 相似文献
65.
Racemic indanofan [(+/-)-1] was efficiently converted to enantiopure (S)-indanofan [(S)-1] by a combination of enzymatic resolution and chemical inversion techniques. An additional important technique is the use of an o-xylene complex of a hemiketal (S)-3c as a precursor, which can be quantitatively converted to (S)-indanofan and easily purified by recrystallization from o-xylene. 相似文献
66.
As part of a series of elucidation of the structural features of peptides caused by C-terminal alpha-amidation, the crystal structures of H-Val-Gly-NH2, H-Ser-Phe-NH2, H-Gly-Tyr-NH2, and H-Pro-Tyr-NH2 hydrochloride salts were analyzed by the X-ray diffraction method. Although respective molecules take energetically allowable torsion angles concerning the backbone and side chains, their conformations are not necessarily the same as the corresponding unamidated ones. This results from the different molecular packing requirements, rather than from different conformational features inherent in the C-amidated and -unamidated peptides. As for the molecular packing feature, each peptide tended to form a repeated structure through those hydrogen bonds in which both amide NH and O=C groups participate. The chloride ions are located between the neighboring peptides and are hydrogen-bonded to the respective amide NHs, leading to the sheet structure. The hydrogen-bonding feature of the amide group and its function in molecular packing was discussed based on the results analyzed so far. 相似文献
67.
Morikawa T Matsuda H Sakamoto Y Ueda K Yoshikawa M 《Chemical & pharmaceutical bulletin》2002,50(8):1045-1049
Two new farnesane-type sesquiterpenes, hedychiols A and B 8,9-diacetate, were isolated from the methanolic extract of the fresh rhizome of Hedychium coronarium KOEN. cultivated in Japan. Their stereostructures were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects of isolated constituents on the release of beta-hexosaminidase from RBL-2H3 cells were examined, and hedychilactone A and coronarin D were found to show the inhibitory activity. 相似文献
68.
Hajime Shigemitsu Youhei Tani Tomoe Tamemoto Tadashi Mori Xinxi Li Yasuko Osakada Mamoru Fujitsuka Toshiyuki Kida 《Chemical science》2020,11(43):11843
The development of photocatalysts is an essential task for clean energy generation and establishing a sustainable society. This paper describes the aggregation-induced photocatalytic activity (AI-PCA) of amphiphilic rhodamines and photocatalytic functions of the supramolecular assemblies. The supramolecular assemblies consisting of amphiphilic rhodamines with octadecyl alkyl chains exhibited significant photocatalytic activity under visible light irradiation in water, while the corresponding monomeric rhodamines did not exhibit photocatalytic activity. The studies on the photocatalytic mechanism by spectroscopic and microscopic analyses clearly demonstrated the AI-PCA of the rhodamines. Moreover, the supramolecular assemblies of the rhodamines exhibited excellent photocatalytic hydrogen evolution rates (up to 5.9 mmol g−1 h−1).Simple amphiphilic rhodamines formed supramolecular assemblies and exhibited aggregation-induced photocatalytic activity and hydrogen evolution in water. 相似文献
69.
Yoshinori SaitoMayu Ichihara Yasuko OkamotoXun Gong Chiaki KurodaMotoo Tori 《Tetrahedron letters》2011,52(48):6388-6391
Five new 1β-angeloyloxyeremophilanolides (subspicatins H-L) and 1β-angeloyloxytetranoreremophilanone (norsubspicatin A), were isolated from the EtOAc extracts of Parasenecio petasitoides and their structures established on the basis of spectroscopic analyses. They are biogenetically mutually related to each other and represent a new category in the Parasenecio group. These findings suggest that there is diversity in this species, too. 相似文献
70.
Dr. Hidetoshi Noda Yasuko Asada Dr. Tatsuro Maruyama Dr. Naoki Takizawa Dr. Nobuo N. Noda Prof. Dr. Masakatsu Shibasaki Dr. Naoya Kumagai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(17):4299-4304
A new scaffold for producing efficient organic fluorescent materials was identified: 2,5-diamino-4,6-diarylpyrimidine featuring a C4N4 elemental composition. Single-step installation of two aryl groups at the 4,6-positions of the pyrimidine core delivered fluorescent organic materials in a modular fashion. A range of fluorescent compounds with distinct absorption/emission properties was readily accessed by changing the aromatic attachments. A generally high absorption coefficient and quantum yield were observed, including C4N4 derivatives that could fluoresce even in the solid state. The two amino groups at the 2,5-positions of the pyrimidine were essential for intense fluorescence with a large Stokes shift, which was corroborated by structural relaxation to a p-iminoquinone-like structure in the excited state. Besides live-cell imaging capabilities, fluorescent labeling of a protein involved in autophagy elucidated a new protein–protein interaction, supporting potential utility in bioimaging applications. 相似文献