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101.
Akira Hasegawa Minoru Morita Hideharu Ishida Makoto Kiso 《Journal of carbohydrate chemistry》2013,32(4):579-588
Abstract Various types of the O-protected derivatives and the 9-bromo analogs of methyl [2-(trimethylsilyl)ethyl 5-acetamido-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosid]onate were synthesized from methyl [2-(trimethyl-silyl)ethyl 5-acetamido-4,7-di-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosid]onate (1) or methyl [2-(trimethylsilyl)ethyl 5-acetamido-8,9-di-O-isopropylidene-D-glycero-α-D-galacto-2-nonulopyranosid]onate (3). 相似文献
102.
Eiji Tanahashi Katsutoshi Murase Mika Shibuya Yumie Igarashi Hideharu Ishida Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(6):831-858
Abstract A systematic synthesis of sulfatide (I) and novel sulfatide analogs (II-VI) carrying 2-(tetradecyl)hexadecyl group as a ceramide substitute is described. The 3-O-, 4-O- and 3,4-di-O-levulinoyl derivatives of galactopyranosyl trichloroacetimidates (1, 12, and 13) were coupled with (2S,3R,4E)-3-O-acetyl-2-octadecanamido-4-octadecene-1,3-diol or 2-(tetradecyl)hexadecan-1-ol. The resulting glycolipids (2, 4, 14, and 15) were each transformed, by selective removal of the levulinoyl group(s), and successive sulfation and de-O-acylation, into the 3-sulfates (I, II), 4-sulfate (III), and 3,4-disulfate (IV). The 6-sulfate (V) was prepared from 2-(tetradecyl)hexadecyl β-D-galactopyranoside (21) via the 6-O-t-butyldimethylsilyl derivative, while the 3′-sulfate of 2-(tetradecyl)hexadecyl β-D-lactoside (VI) was synthesized from 2-(trimethylsilyl)ethyl 3′-O-benzyl-β-D-lactoside (26). The structures of the sulfated glycolipids (I-VI) were characterized by ion-spray MS, MS/MS, and 1H NMR spectrometry. 相似文献
103.
Koji Seto Hiroshi Shimojitosyo Hideyuki Imazaki Hiroshi Matsubara Shigetoshi Takahashi 《Liquid crystals》2013,40(4):517-518
Abstract Chiral 1, 2-diphenylethane derivatives have been synthesized and found to form stable chiral Sc phases exhibiting ferroelectric properties. Comparison with diphenylacetylene derivatives revealed that flexibility of the bridging groups between two benzene nuclei strongly influences the stability of mesophases as well as transition temperatures. 相似文献
104.
Tomohiro Terada Hirofumi Simada Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(4-5):519-534
Abstract KDN-Lex ganglioside analogs (10, 13, 16 and 19) containing the modified reducing terminal and L-rhamnose in place of L-fucose have been synthesized. Glycosidation of methyl 2,3,4-tri-O-benzyl-1-thio-α-L-rhamnopyranoside (1) with 2-(trimethylsilyl)ethyl O-(2-acetamido-4,6-O-benzylidene-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-α-D-galacopyranoside (2), followed by reductive ring opening of the benzylidene acetal, gave 2-(trimethylsilyl)ethyl O-(2,3,4-tri-O-benzyl-α-L-rhamnopyranosyl)-(1→3)-O-(2-acet-amido-6-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 (4). The tetrasaccharide 4 was coupled with methyl O-(methyl 4,5,7,8,9-penta-O-acetyl-3-deoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-D-galactopyranoside(5), using dimethyl(methylthio)sulfonium triflate (DMTST), to give the hexasaccharide 6, which was converted into compound 11 in the usual manner. Compounds 8 and 11 were transformed, via bromination of the reducing terminal, radical reduction, O-deacylation and saponification of the methyl ester, into the desired KDN-Lex hexasaccharides (10, 13). On the other hand, glycosylation of 2-(tetradecyl)hexadecanol with α-trichloroacetimidates 14 and 17, afforded the target ganglioside analogs 16 and 19. 相似文献
105.
Y. Kuga M. Hirasawa T. Seto K. Okuyama K. Takeuchi 《Applied Physics A: Materials Science & Processing》1999,68(1):75-80
5 nanoparticles equipped with an in situ size-monitoring system, a LPDMA (low-pressure differential mobility analyzer), was
developed to experimentally investigate the nanoparticle growth mechanism. The concentration of photoproduced UF5 molecules was controlled by changing three factors: (I) the concentration of the feed UF6 gas, (II) the laser pulse energy of the irradiation, and (III) the repetition rate of the laser pulses. The dependence of
the volumetric average diameter of the photoproduced particles on the UF5 nascent concentration in all three cases was found to be very similar. The result strongly suggests that the reactor functions
as a mixed-flow reactor under a complete mixing condition. The particle size measured by the LPDMA was found to be in the
range of 6 to 11 nm, and it was approximately proportional to the power 0.3 of the initial concentration of photoproduced
UF5 molecules.
Received: 11 May 1998/Accepted: 15 September 1998 相似文献
106.
Hitoshi Okuda Ryota Seto Yasuhito Koyama Toshikazu Takata 《Journal of polymer science. Part A, Polymer chemistry》2010,48(19):4192-4199
Poly(arylene thioether)s ( PTEs ) containing 9,9′‐spirobifluorene moieties were synthesized in high yields from 9,9′‐spirobifluorene‐2,2′‐bis(N,N‐dimethylcarbamothioate) 4 as the masked dithiol and various difluoroarenes as electrophilic monomers. All PTEs showed high thermal stability: The 10% weight loss temperature as evaluated by thermogravimetric analysis was over 470 °C under both nitrogen and air atmospheres. The glass transition temperature estimated by DSC was in the range 210–270 °C. The PTEs showed high solubility in ordinary organic solvents, such as CHCl3, NMP, and THF. Most PTEs exhibited remarkably high refractive indices ranging from 1.69 to 1.73 at 587.6 nm, whereas no or little birefringence was observed for the PTEs . © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4192–4199, 2010 相似文献
107.
108.
The methoxymethyl protecting group for carbinols is best removed from acid-sensitive substrates by hydrolysis in aqueous methanol using a cationic exchange resin (Dowex-50W). 相似文献
109.
Ryota Seto Kozo Matsumoto Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2013,51(24):5221-5229
Radical copolymerizations of 2‐isothiocyanatoethyl methacrylate (ITEMA) and 2‐hydroxyethyl methacrylate (HEMA) or methacrylic acid (MAA) were examined, and fundamental properties of the obtained copolymers were investigated. The copolymerizations of various ITEMA/HEMA or ITEMA/MAA compositions proceeded effectively in THF or DMF by using 2,2′‐azobisbutyronitrile (AIBN) as an initiator, keeping the isothiocyanato groups and hydroxyl or carboxyl groups unchanged. Glass transition temperatures (Tg)s of poly(ITEMA‐co‐HEMA)s ranged from 68 to 100 °C, and they were thermally stable up to 200 °C. Meanwhile, Tgs of poly(ITEMA‐co‐MAA)s (ITEMA/MAA = 91/9, 76/24) were determined to be 91 and 109 °C, respectively. However, poly(ITEMA‐co‐MAA)s were thermally unstable, and significant weight loss was observed around 180 °C, which may be due to an addition of carboxyl groups to isothiocyanato groups followed by an elimination of COS to form amide structure in the copolymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5221–5229 相似文献
110.
Hide-Ki Ishida Hiromune Ando Hiromi Ito Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(4-5):413-428
Abstract A first total synthesis of gangliosides GD1c and GT1a containing Neu5Acα(2→8) Neu5Acα(2→3)Gal residue in their non-reducing terminal is described. Condensation of methyl O-[methyl 5-acetamido-8-O-(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylono-11,9-lactone) -4,7- di-O-acetyl-3,5-dideoxy-D-glycero-α-D-galcto-2-nonulopyranosyranosylanate]-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-D-gala-ctopyranoside (1) with 2-(trimethylsilyl)ethyl O-(2-acetamido-4,6-O-benzylidene-2-deoxy-β-D-galactopyranosyl)- (1→4) -O -(2,3,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (2) or 2-(trimethylsilyl)ethyl O-(2-acetamido-6-O-benzyl-2-deoxy-β-D-galactopyranosyl)-(1→4)-(9-[methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)]-O-(2,6-di-O-benzyl-β-D-galactopyranosyl) - (1→4) - 2,3,6-tri-O-benzyl-β-D-glucopyranoside (3) in the presence of dimethyl(methylthio)sulfonium triflate (DMTST) gave the corresponding hexa-and heptasaccharide derivatives 4 and 5, respectively. These oligosaccharides were converted into the α-trichloroacetimidates 10 and 11 via reductive removal of the benzyl groups and/or benzylidene group, O-acetylation, selective removal of the 2-(trimethylsilyl)ethyl group and treatment with trichloroacetonitrile, which, on coupling with 2-azidosphingosine derivatives 12 or 13, gave the β-glycosides 14 and 15, respectively. Finally, 14 and 15 were transformed, via selective reduction of the azido group, coupling with octadecanoic acid and removal of all protecting groups, into the title gangliosides GD1c 18 and GT1a 19. 相似文献