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31.
A convergent synthesis of the A-F ring segment of yessotoxin and adriatoxin was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis. 相似文献
32.
Shoichi Katsuta Hirokazu Wakabayashi Mariko Tamaru Yoshihiro Kudo Yasuyuki Takeda 《Journal of solution chemistry》2007,36(4):531-547
Equilibria concerning picrates of tetraalkylammonium ions (Me4N+, Et4N+, Pr4N+, Bu4N+, Bu3MeN+) in a dichloromethane−water system have been investigated at 25 ∘C. The 1:1 ion-pair formation constants (K
IP,o
o) in dichloromethane at infinite dilution were conductometrically determined. The distribution constants (K
D
o) of the ion pairs and the free cations between the solvents were determined by a batch-extraction method. The K
IP,o
o value varies in the cation sequence, Bu4N+ ≈ Pr4N+ ≈ Et4N+ < Bu3MeN+ < < Me4N+; this trend is explained by the electrostatic cation−anion interaction taking into account the structures of the ion pairs
determined by density functional theory calculations. For the ion pairs of the symmetric R4N+ cations, there is a linear positive relationship between log10
K
D
o and the number of methylene groups in the cation (N
CH
2). The ion pair of asymmetric Bu3MeN+ has a higher distribution constant than that expected from the above log10
K
D
o
versus
N
CH
2 relationship. These cation dependencies of log10
K
D
o for the ion pairs are explained theoretically by using the Hildebrand-Scatchard equation. For all the cations, the log10
K
D
o value of the free cation increases linearly with N
CH
2; the variation of log10
K
D
o is discussed by decomposing the distribution constant into the Born-type electrostatic contribution and the non-Born one,
and attributed to the latter that is governed by the differences in the molar volumes of the cations. The cation dependencies
of the ion-pair extractability and ion pairing in water are also discussed.
An erratum to this article can be found at 相似文献
33.
[reaction: see text] We describe an efficient synthesis of di-branched heptasaccharide 1 having phytoalexin elicitor activity in soybeans by one-pot glycosylation. The synthesis involves chemo- and regioselective sequential six-step glycosylations using seven independent building blocks and sequential removal of acyl- and benzyl ether-type protecting groups. The coupling of seven building blocks requires only four chemoselective activitable leaving groups of glycosyl donors. Both the glycosylation and deprotection reactions can be achieved utilizing a parallel manual synthesizer. 相似文献
34.
Oishi T Hagiwara K Kinumi T Yamakawa Y Nishijima M Nakamura K Arimoto H 《Organic & biomolecular chemistry》2003,1(15):2626-2629
The effects of Soto's 'beta-sheet breaker peptide' and its polymer on PrPSc formation in ScN2a cells were investigated. Surface plasmon resonance study indicated that direct binding between PrP(81-145) and the 'beta-sheet breaker peptide' is not specific and may not play a major role in the inhibition of PrPSc formation. 相似文献
35.
Precipitation temperature-total polymer concentration diagrams for toluene solutions of two styrene-acrylonitrile copolymers different in chemical composition and their mixtures were determined and then triangular phase diagrams of this system were constructed from these diagrams. It is speculated from the triangular phase diagrams and experimentally shown that the copolymer may be effectively fractionated by chemical composition in this system. 相似文献
36.
Chihiro Manri Takahide Yokoi Hirokazu Nishida 《Applied biochemistry and biotechnology》2017,182(2):609-623
Extracellular vesicles (EV), typified by exosomes or microvesicles, are expected to be effective diagnostic markers for cancers. The sizes of the vesicles range from 20 to 1000 nm, but the size-dependent variations of the contents of EVs are still poorly understood. We succeeded in the size-selective harvesting of the vesicles by utilizing the molecular weight-dependent characteristics of a variety of polyethylene glycols (PEG) as precipitating reagents and analyzed the antigens displayed on the surfaces of the vesicles and the miRNAs included in the vesicles from each size group. As a result, the relatively larger (<100 nm) particles precipitated by PEG5k clearly exhibited the greatest amount of epithelial cell adhesion molecule (EpCAM), from both breast cancer (MCF-7) and colon cancer (HCT116) cells, and a larger quantity of microRNA (miRNA) specific to breast cancer cells (miRNA155 for MCF-7) seemed to be contained in the PEG-precipitated particles. The results demonstrated that the quantities of both the tumor-specific miRNA and protein were similarly distributed among the several classes of the size-sorted EVs and that the size-selective harvesting of EVs may be informative for strategic analyses towards the diagnoses of cancers. 相似文献
37.
38.
On the ‐boundedness of solution operator families of the generalized Stokes resolvent problem in an infinite layer 下载免费PDF全文
Hirokazu Saito 《Mathematical Methods in the Applied Sciences》2015,38(9):1888-1925
In this paper, we prove the ‐boundedness of solution operator families of the generalized Stokes resolvent problem in an infinite layer with resolvent parameter , where , and our boundary conditions are nonhomogeneous Neumann on upper boundary and Dirichlet on lower boundary. We want to emphasize that we can choose 0 < ? < π ∕ 2 and γ0 > 0 arbitrarily, although usual parabolic theorem tells us that we must choose a large γ0 > 0 for given 0 < ? < π ∕ 2. We also prove the maximal Lp ? Lq regularity theorem of the nonstationary Stokes problem as an application of the ‐boundedness. The key of our approach is to apply several technical lemmas to the exact solution formulas of a resolvent problem. The formulas are obtained through the solutions of the ODEs, in the Fourier space, driven by the partial Fourier transform with respect to tangential space variable . Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
39.
Jun Yamamoto Nami Maeda Chiaki Komiya Tomohiro Tanaka Masaya Denda Koji Ebisuno Wataru Nomura Hirokazu Tamamura Youichi Sato Aiko Yamauchi Akira Shigenaga Akira Otaka 《Tetrahedron》2014
A fluoride-responsive (FR) amino acid that induces amide bond cleavage upon the addition of a fluoride was developed, and it was applied to an FR traceable linker. By the use of an alkyne-containing peptide as a model of an alkynylated target protein of a bioactive compound, introduction of the FR traceable linker onto the peptide was achieved. Subsequent fluoride-induced cleavage of the linker followed by labeling of the released peptide derivative was also conducted to examine the potential applicability of the FR traceable linker to the enrichment and labeling of alkynylated target molecules. 相似文献
40.
Xiaolei Wang Miho Emoto Atsushi Sugimoto Yusuke Miyake Kaori Itto Mitsuo Amasaka Shu Xu Hiroshi Hirata Hirotada Fujii Hirokazu Arimoto 《Tetrahedron letters》2014
A scalable synthetic route for 15N-labeled 4-oxo-2,2,6,6-tetraethylpiperidine nitroxide (15N-TEEPONE) is described. This 15N-labeled nitroxide is suitable for electron paramagnetic resonance imaging of brain, and its higher sensitivity compared with that of its 14N-counterpart is an important advantage of the labeled derivative. 相似文献