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151.
Yukihiro Isogai Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(9):1119-1137
ABSTRACT 3-O-Sulfo glucuronyl neolactohexanosyl ceramide derivatives (heptasaccharides) have been synthesized. Condensation of 2-(trimethylsilyl)ethyl 2,4,6-tri-O-benzyl-β-D-galactopyranoside (2) with 4-O-acetyl-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl trichloroacetimidate (1) gave the desired β-glycoside 3, which was converted into 2-(trimethylsilyl)ethyl O-(2-acetamido-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranosyl)-(1→3)-2,4,6-tri-O-benzyl-β-D-galactopyranoside (4) via removal of the O-acetyl and N-phthaloyl groups, followed by N-acetylation. Glycosylation of 4 with O-(methyl 4-O-acetyl-2-O-benzoyl-3-O-levulinoyl-β-D-glucopyranosyluronate)-(1→3)-2,4,6-tri-O-benzoyl-α-D-galactopyranosyl trichloroacetimidate (5) using trimethylsilyl trifluoromethanesulfonate gave the target tetrasaccharide 6, which was transformed via removal of the benzyl group, O-benzoylation, removal of the 2-(trimethylsilyl)ethyl group and imidate formation into the tetrasaccharide donor 9. Glycosylation of 2-(trimethylsilyl)ethyl O-(2-acetamido-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (10) with the imidate donor 9 using trimethylsilyl trifluoromethanesulfonate gave the desired heptasaccharide 11, which was transformed into the heptasaccharide imidate donor 14. Glycosylation of (2S, 3R, 4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (15) with 14 gave β-glycoside 16, which was transformed into the four target compounds, via reduction of the azido group, coupling with octadecanoic acid or tetracosanoic acid, selective removal of the levulinoyl group, O-sulfation, hydrolysis of the methyl ester group and O-deacylation. 相似文献
152.
Polysialoglycoconjugates, such as polysialylated ganglio-series gangliosides and N-CAM (neural cell adhesion molecule), are of interest because of their important physiological functions in association with neural cell development, differentiation, neuron network formation, and so on.2-4 Chemical synthesis of these glycoconjugates provides an effective method to elucidate their biological significance in nature at the molecular level, providing not only genuine original glycoconjugates but also their derivatives and analogs designed for biological investigation. We have established5 an efficient method to construct dimeric and trimeric sialoglycosides by using the lactonated sialic acid derivatives as building blocks, and succeeded in the systematic synthesis of various polysialogangliosides such as GD3, GQ1b, GQlbα and, very recently, GT3.6 In this paper, as a part of our continuous synthetic approach directed toward the polysialoglycoconjugates, we report the first synthesis of α-linked tetrameric sialoglycosides coupled with a galactose and lactose residue. 相似文献
153.
Akihiko Kameyama Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(4):549-560
ABSTRACT The first total synthesis of tumor-associated glycolipid antigen, sialyl Lewis X is described. Glycosylation of 2-(trimethylsilyl)ethyl O-(2-acetamido-4,6-O-benzylidene-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (1) with methyl 2,3,4-tri-O-benzyl-1-thio-β-L-fuco-pyranoside (4) gave the α-glycoside (5), which was converted by reductive ring-opening of the benzylidene acetal into the glycosyl acceptor (6). Dimethyl(methylthio)sulfonium triflate-promoted coupling of 6 with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-D-galactopyranoside (7) afforded the desired hexasaccharide 8 in good yield. Compound 8 was converted into the α-trichloroacetimidate 11, via reductive removal of the benzyl groups, O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, and treatment with trichloroacetonitrile, which, on coupling with (2S, 3R, 4E)-2-azido-3-O-benzoyl-4-octa-decene-1,3-diol (12), gave the β-glycoside 13. Finally, 13 was transformed, via selective reduction of the azide group, condensation with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester group, into the title compound 16. 相似文献
154.
Yuji Ogawa Motoji Wakida Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(3):433-446
Abstract To investigate the biological influence of the 2-(acyloxy)tetradecanoyl and 2-hydroxyacyl groups in the nonreducing-sugar subunit analogs of lipid A, a novel series of 3-(O-[(2RS)-2-acyloxytetradecanoyl]-2-deoxy-2-[(2RS)-2-hydroxytetradecanamido]-4-O-phosphono-d-glucoses (10a-d), 3-O-[(2RS)-2-acyloxytetradecanoyl]-2-deoxy-2-[(3R)-3-hydroxytetradecanamido]-4-O-phosphono-d-glucoses (19a-d), and 2-deoxy-2-[(2RS)-2-hydroxyacyl]amino-4-O-phosphono-3-O-[(3R)-3-tetradecanoyloxytetradecanoyl]-d-glucoses (23e-h) were systematically synthesized. 相似文献
155.
This article is devoted to the study of the Cauchy problem in Gevrey classes for some higher order weakly hyperbolic equations
with time-dependent coefficients and without lower order terms. 相似文献
156.
The future muon facility planned for the future Japanese accelerator project (Japanese Hadron Project) and related activities
towards advanced muon facilities are described. 相似文献
157.
Takashi Ishida Mamoru Shoji Yoshiyuki Miyabata Yasumasa Shibata Eiji Ohno Shunji Ohaira 《Optical Review》1994,1(2):183-187
A high density mark edge recording method on a phase change rewritable disk is reported. A carrier-to-noise ratio of 55 dB for a mark length of 0.55,μm is obtained by using a 680 nm, NA 0.6 head and a phase change rewritable disk. In mark edge recording, it is necessary to record each mark in correct length. A new laser power modulation pattern is proposed. This pattern consists of a first-pulse, a multi-pulse chain and a last-pulse. Both positions of the first-ptilse and the last-pulse are movable. By adjusting these positions, a jitter, σ/Tw (Tw is window margin), is improved to 6.5% in high density EFM (Eight to Fourteen Modulation) recording of 0.4 μm/bit. 相似文献
158.
F.L. Pratt S.J. Blundell P.A. Pattenden W. Hayes K.H. Chow A.P. Monkman T. Ishiguro K. Ishida K. Nagamine 《Hyperfine Interactions》1997,106(1-4):33-38
We report studies of spin dynamics in the conducting polymers polyaniline and polypyrrole using both μ+SR and μ-SR techniques. These measurements reveal characteristic field dependences and cutoff frequencies for the muon spin relaxation
which can be related to the spin diffusion process. Clear evidence is seen for increased spin localisation at low temperatures
where a crossover occurs from two or three dimensional spin diffusion to a one dimensional diffusion regime.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
159.
The crystallization behavior, via annealing, of PEEK was investigated using FTIR spectroscopy. It was found that predominantly amorphous PEEK (e.g., quenched polymer) follows two distinct mechanisms when it is annealed. One is a lower energy relaxation process that involves the partial rotation of the ether linkages, allowing the molecular chains in the disordered phase to become better packed, and occurs from 50 to 140°C (slightly below Tg). This relaxation process is also observed by dynamic mechanical analyses. The other process is a crystallization that takes place above the glass transition, with its onset characterized by the rotation of the benzophenone linkages near Tg. Isothermal crystallization kinetics data on PEEK can be described by an Avrami equation with an Avrami constant n of about 1. 相似文献
160.
The influence of cell density of cells cryopreserved inside a collagen matrix at various cooling rates was investigated. Human fibroblasts were three-dimensionally cultured for 2 days in a collagen sponge (20 mm in diameter and 1 mm in thickness) as an extracellular matrix to imitate biological tissue (artificial tissue). Different cell densities for the artificial tissue were used, from 10(5) to 10(7) cells/cm(3). Four artificial tissues were first stacked in a test chamber, frozen at a cooling rate of 0.3 to 50 degrees C/min in a solution of Dulbecco's Modified Eagle Medium, 20% fetal bovine serum and 10% dimethylsulfoxide, kept frozen below -185 degrees C for 2 hours, and then finally thawed. Membrane integrity of fibroblasts using a trypan blue exclusion assay was evaluated as an index for post-thaw cellular viability. Results show that with increasing cell density, the post-thaw membrane integrity decreased. Therefore, in the cryopreservation of biological tissue, it seems high cell density is one factor which causes a decline in viability. 相似文献