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1.
A simple method to label oligosaccharides with a multifunctional fluorescent group was developed. Oligosaccharides were quantitatively labeled at their reducing termini with pyrene butanoic acid hydrazide. The pyrene-labeled oligosaccharides were successfully applied to fluorescence polarization measurements and ELISA at picomole quantity, which was not previously reached by other procedures. This labeling method should prove to be useful in a variety of aspects in glycobiology. 相似文献
2.
Kohtaro Goto 《Tetrahedron letters》2005,46(48):8293-8297
A hexakis(fluorous chain)-type alcohol was used in the synthesis of oligosaccharides and peptides through connection with a linker suitable for the particular type of target compound. After the preparation of the desired compound, the fluorous alcohol was easily recovered in good yields under basic conditions. It appears that the fluorous alcohol can be recovered, recycled, and reused. 相似文献
3.
Four possible diastereomers of pentenocin B were synthesized in a stereocontrolled manner, and the first total synthesis of a natural enantiomer of (+)-pentenocin B unequivocally established the absolute stereochemistry to be 4S,5R,6R. 相似文献
4.
Polysiloxane formation in dimethyldiethoxysilane (DMDES)-ethyl alcohol (EtOH(D))-oxalic acid (OA) (DMDES:EtOH(D):OA=1:2:0.5) and DMDES-dimethylsulfoxide (DMSO)-OA (DMDES:DMSO:OA=1:2:0.5) systems was investigated by gas chromatography-mass spectrometry and 29Si-nuclear magnetic resonance. While the DMDES-EtOH(D)-OA system was homogeneous, the DMDES-DMSO-OA system consisted of two immiscible phases. In both systems, ethoxy-terminated linear oligomers ((EtO)Me2SiO(Me2SiO)nSiMe2(OEt); n=0–4, Et = C2H5, Me = CH3) and cyclic tetramer ((Me2SiO)4) were identified. The reaction mechanism for polysiloxane formation is discussed. 相似文献
5.
A concise route to (-)-kainic acid from enantiopure (+)-cis-4-carbobenzoxyamino-2-cyclopentenol has been devised by employing concurrent Chugaev syn-elimination and intramolecular ene reaction as the key step. 相似文献
6.
7.
Yoshizumi Ishikawa Hideyasu Honda Yoshiyuki Sugahara 《Journal of Sol-Gel Science and Technology》2000,19(1-3):365-369
The conversion of tetrakis(diethylamino)titanium (Ti(NEt2)4) into titania via either a combination of hydrolysis (Ti(NEt2)4 : THF : H2O = 1 : 10 : x, x = 2, 4, 10) at ambient conditions and calcination (method A) or hydrolysis in a water-tetrahydrofuran (THF) mixture (Ti(NEt2)4 : THF : H2O = 1 : 10 : 100) at reflux (method B) was investigated. Titanium tertiary butoxide (Ti(O
t
Bu)4) was also used as a substitute for Ti(NEt2)4. The hydrolysis via method A resulted in the formation of amorphous solids containing organics. Thermal analyses showed that the hydrolysis products showed mass losses up to 500°C probably due to the presence of diethylamine (Et2NH) formed via the hydrolysis of Ti(NEt2)4 in the hydrolysis products, while a mass loss of the hydrolysis product from Ti(O
t
Bu)4 was completed up to about 200°C. After calcination at 600°C, anatase or a mixture of anatase and rutile was obtained. The crystallization behavior of the hydrolysis products from Ti(NEt2)4 was different from that of the hydrolysis product from Ti(O
t
Bu)4. The hydrolysis via method B gave only an amorphous material from Ti(NEt2)4, while a crystalline titania (anatase and brookite) formed from Ti(O
t
Bu)4. 相似文献
8.
pi-Allyl-nickel complexes initiated addition polymerisation of 2-phenyl-1-methylenecyclopropane to give a polymer with three-membered rings; the formed polymer showed a high Tg and negligible thermal decomposition up to 300 degrees C. 相似文献
9.
Momoko Ishida Rika Ohara Fuka Miyagawa Hiroe Kikuzaki Kosuke Nishi Hiroyuki Onda Nanami Yoshino Takuya Sugahara 《Molecules (Basel, Switzerland)》2022,27(13)
Cuminum cyminum L. (cumin) is an annual plant of the Umbelliferae family native to Egypt. We previously showed that the aqueous extract of cumin seeds suppresses degranulation by downregulating the activation of antigen-induced intracellular signaling molecules in rat basophilic leukemia RBL-2H3 cells. However, the active substances in the extract have not yet been identified. Accordingly, herein, we aimed to ascertain the water-soluble substances present in cumin seeds that inhibit degranulation, which led to the identification of umbelliferose, a characteristic trisaccharide present in plants of the Umbelliferae family. Our study is the first to reveal the degranulation-suppressing activity of umbelliferose, and quantification studies suggest that cumin seed powder contains 1.6% umbelliferose. Raffinose, an isomer of umbelliferose, was also found to significantly suppress antigen-induced degranulation, but less so than umbelliferose. Both umbelliferose and raffinose contain sucrose subunits in their structures, with galactose moieties bound at different sites. These differences in structure suggest that the binding of galactose to the sucrose subunit at the α1-2 bond contributes to its strong degranulation-inhibiting properties. 相似文献
10.
Olefin Polymerization Catalyzed by Double‐Decker Dipalladium Complexes: Low Branched Poly(α‐Olefin)s by Selective Insertion of the Monomer Molecule 下载免费PDF全文
Dr. Shigenaga Takano Dr. Daisuke Takeuchi Prof.Dr. Kohtaro Osakada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):16209-16218
Dipalladium complexes of a cyclic bis(diimine) ligand with a double‐decker structure catalyze polymerization of ethylene and α‐olefins and copolymerization of ethylene with 1‐hexene. The polymerization of 1‐hexene yields a polymer that is mainly composed of the hexamethylene unit formed by 2,1‐insertion of the monomer into the palladium–carbon bond, followed by chain‐walking (6,1‐insertion). The polymerization of 4‐methyl‐1‐pentene proceeds by 2,1‐insertion with a selectivity of 92–97 %, and affords the polymer with methyl and 2‐methylhexyl branches. 2,1‐Insertion occurs selectively in all of the polymerization reactions of α‐olefins catalyzed by the dipalladium complexes. Ethylene polymerization with the catalyst at 100 °C lasts over 24 h, whereas the monopalladium–diimine catalyst loses its activity within 8 h at 60 °C. Polyethylene obtained by the dipalladium catalyst is less‐branched and has a higher molecular weight compared to that of the monopalladium catalyst under the same conditions. Copolymerization of ethylene with 1‐hexene affords solid products with melting points and molecular weights that vary depending on the polymerization time, suggesting formation of a block and/or gradient copolymer. 相似文献