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101.
Wang NH Taniguchi M Tsuji D Doi M Ohishi H Yoza K Baba K 《Chemical & pharmaceutical bulletin》2003,51(1):68-70
Four new guaianolides, sinodielides A-D (1-4), were isolated from Sinodielsia yunnanensis WOLFF together with a known polyacetylene, falcarindiol, and two known coumarins, bergapten and scopoletin. Their structures were established by spectral and X-ray analyses. 相似文献
102.
Otsuka H Kijima H Hirata E Shinzato T Takushi A Bando M Takeda Y 《Chemical & pharmaceutical bulletin》2003,51(3):286-290
Five megastigmane glucosides were isolated from the leaves of Glochidion zeylanicum. One of them was a known compound, blumenol C O-beta-D-glucopyranoside (1), and the structures of the four new compounds, glochidionionosides A-D (2-5), were mainly elucidated by spectroscopic methods, including a modified Mosher's method. The absolute configurations of the six-membered ring of glochidionionoside D (5) were deduced by beta-D-glucopyranosylation-induced shift trends in the (13)C-NMR spectra and confirmed by X-ray analysis as its p-bromobenzoate (5b), and the axis chirality of C-7 was determined to be R. 相似文献
103.
Ikushima Y Hatakeda K Sato O Yokoyama T Arai M 《Angewandte Chemie (International ed. in English)》2001,40(1):210-213
104.
Shin-ichi Wada Masahiko Takigawa Kazuhiro Matsushita Hiroyuki Kizaki Kenichiro Tanaka 《Surface science》2007,601(18):3833-3837
Methyl mercaptoacetate (MA) on Cu(1 1 1) surface was investigated using synchrotron radiation-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. MA adsorbs on the surface via thiolate formation and weak interaction of the carbonyl group with the surface. Two different adsorption states previously reported for methanethiolate and ethanethiolate were confirmed, besides atomic sulfur. NEXAFS measurements support gauche-type conformation of MA whose skeleton lies on the surface. 相似文献
105.
Ken Tachibana Ken Takeda Masahiko Shiraishi 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(7):342
It is well-recognized that DNA methylation and histone modifications play critical roles in epigenetic regulation of gene activity through the alteration of chromatin structure. Recent studies have shown that in a subset of cancer cells, the silencing of the human E-cadherin (CDH1) gene is associated with hypermethylation of the CpG island. However, the associated molecular mechanism remains unclear. To understand the mechanism, we have investigated the alteration of CpG island methylation and histone modifications during the reactivation of the CDH1 gene by treatment with 5-aza-2′-deoxycytidine (5-aza-dC). Although the CDH1 gene expression was recovered by treatment with 5-aza-dC in a liver cancer cell line Li21, the methylation status of the entire CpG island and acetylation and methylation status of associated histones were not significantly altered. These results demonstrate that the silenced CDH1 gene can be reactivated without apparent alteration of histone modification or CpG island methylation. 相似文献
106.
Hidetsura Cho Yoshio Nishimura Yoshizumi YasuiSatoshi Kobayashi Shin-ichiro Yoshida Eunsang Kwon Masahiko Yamaguchi 《Tetrahedron》2011,67(14):2661-2669
Synthesis of novel 4-unsubstituted dihydropyrimidines (DPs) was performed. Subsequently, a variety of 4-unsubstituted 1,4(3,4)-DPs with amino moieties at position-2 were obtained in excellent yields by activation of position-2 owing to regioselective alkoxycarbonylation at position-3 of the DP skeleton. 3-Oxo-2-phenyl-2,3,5,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrimidine was obtained using phenylhydrazine instead of amines. Individual tautomers of 1,4(3,4)-DP were observed in the 1H NMR spectra of one derivative depending on temperature and concentration. On the other hand, only 1,4-DP was found in the solid state by single-crystal X-ray crystallography. 相似文献
107.
Takamitsu Otake Yoshie Aoyagi Takashi Yarita Masahiko Numata 《Analytical and bioanalytical chemistry》2010,397(6):2569-2577
Fish certified reference material (CRM), NMIJ CRM 7404-a, for the analysis of polychlorinated biphenyls (PCBs) and organochlorine
pesticides (OCPs) was developed by the National Metrology Institute of Japan, part of the National Institute of Advanced Industrial
Science and Technology. Fish samples (Japanese seabass) used for the preparation of the CRM were collected from Tokyo Bay,
and the edible part was freeze-dried, pulverized, sieved, homogenized, and sterilized by γ-irradiation. This sample is in
the form of a powder comprising approximately 10 g stored in a brown glass bottle. The certification was carried out using
multiple analytical methods such as pressurized liquid extraction, Soxhlet extraction, saponification, and homogenization
to ensure the reliability of analytical results; the certified values of target PCBs (PCB 28, PCB 70, PCB 105, PCB 153, and
PCB 170) and OCPs (trans-nonachlor, dieldrin, p,p′-DDE, p,p′-DDT, and p,p′-DDD) were 1.05–14.0 μg kg−1 and 1.57–18.0 μg kg−1 for PCBs and OCPs, respectively. This is the first fish powder CRM in which PCBs and OCPs were determined by isotope dilution
mass spectrometry. 相似文献
108.
Kazuhisha Hiratani Shamsun Naher Michinori Karikomi Kazuo Haga 《Journal of heterocyclic chemistry》2005,42(4):575-582
Novel crownophanes with 27‐ and 28‐membered rings having two hydroxyl groups, two amide groups, and aromatic moieties such as naphthalene, pyridine, and phenyl rings were successfully synthesized by a one‐step reaction from the corresponding macrocyclic polyethers via “tandem Claisen rearrengement” in moderate yields. They can solubilize urea and its derivatives into chloroform solution, while the corresponding macrocyclic polyethers do not solubilize them. According to NMR studies, crownophanes 1 and 2 interact with urea and its derivatives forming 1:1 complexes. 相似文献
109.
If a vertex operator algebra satisfies , , then has a commutative (nonassociative) algebra structure called Griess algebra. One of the typical examples of commutative (nonassociative) algebras is a Jordan algebra. For example, the set of symmetric matrices of degree d becomes a Jordan algebra. On the other hand, in the theory of vertex operator algebras, central charges influence the properties of vertex operator algebras. In this paper, we construct vertex operator algebras with central charge c and its Griess algebra is isomorphic to for any complex number c and a positive integer d. 相似文献
110.
Masahiko Taniguchi 《Tetrahedron》2010,66(30):5549-5565
A series of (p-phenylene)n-linked meso-mesityl-substituted porphyrin dyads (n=2-4) was prepared via Suzuki coupling of zinc(II) and free base porphyrin building blocks. The resulting zinc(II)/free base porphyrin dyads were demetalated. The series of free base porphyrin dimers (n=1-4), four other porphyrin dimers (with p-phenylene, diphenylethyne or diphenylbutadiyne linkers; and aryl or tridec-7-yl meso substituents), and several benchmark monomers were converted to the thallium(III)chloride complexes under mild conditions. The collection of eight Tl(III)Cl/Tl(III)Cl dimers is designed for studies of ground-state hole-transfer processes and comparison with the excited-state energy- and hole-transfer processes of the corresponding Zn(II)/free base dyads. Altogether, 18 new porphyrin arrays and benchmark monomers have been prepared. 相似文献