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201.
One novel and three known hydroxycinnamic acid derivatives having antioxidant activities were isolated from a Brazilian bee pollen. They were identified as kaempferol 3-O-[2-O-p-coumaroyl]-alpha-L-arabinopyranoside, N(1), N(5), N(10)-tri-p-coumaroyl spermidine, N(1), N(5), N(10), N(14)-tetra-p-coumaroyl spermine, and monocaffeoyl-tri-p-coumaroyl spermine, respectively. The structure of the kaempferol glycoside was established on the basis of spectroscopic and chemical investigations. Among the isolated compounds, monocaffeoyl-tri-p-coumaroyl spermine showed the strongest free radical-scavenging activity, which was almost identical to that of alpha-tocopherol. On the other hand, the antioxidant effect of tri-p-coumaroyl spermidine on autooxidation of linoleic acid was strongest and nearly equal to that of alpha-tocopherol. 相似文献
202.
Toshifumi Satoh Ken Shibata Kazuaki Yokota Toyoji Kakuchi 《Macromolecular rapid communications》1999,20(2):55-58
(2→5)‐1,4‐Anhydro‐3‐O‐methyl‐pentitol, which is a novel carbohydrate polymer without an anomeric linkage, was synthesized by cationic cyclopolymerization of 1,2 : 4,5‐dianhydro‐3‐O‐methyl‐xylitol. When BF3·OEt2 was used as the initiator, soluble polymers were obtained in 28 to 50% yield. These polymers have number‐average molecular weights of 1 150 to 2 340 corresponding to an average degree of polymerization of 8.8 to 18.0. It was confirmed by 13C NMR that the resulting polymer mainly consists of 1,4‐anhydro‐3‐O‐methyl‐D L ‐arabinitol units. 相似文献
203.
204.
Molecularly imprinted continuous polymer rods are prepared inside PEEK tubes of 1 mm i. d. by an in situ preparation technique; and chiral separations on such media have been demonstrated. The miniaturized column filled with (–)‐cinchonidine‐imprinted or (+)‐cinchonine‐imprinted polymer rods based on a copolymer of 2‐(trifluoromethyl)acrylic acid and ethylene glycol dimethacrylate permitted diastereoseparation of (–)‐cinchonidine and (+)‐cinchonine; the template molecule is retained to a greater extent than the corresponding antipode. Increasing the amount of cyclohexanol in the polymerization mixture decreased the backpressure of the resultant rod and the addition of latex beads suspended in water to the prepolymerization mixture affected the selectivity and affinity of the imprinted polymer rods. The column length is adjusted easily by cutting, thus allowing easy control of retention behavior and analysis time. 相似文献
205.
Harumi Kaga Shin Yamane Atsushi Narumi Toshifumi Satoh Toyoji Kakuchi 《Macromolecular Symposia》2004,217(1):29-38
2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) was reacted with 4-ethylphenyl 2,3,4,6-tetra-O-acetyl-β-D -glucopyranoside using tert-butyl hydroperoxide and cobalt(II)acetate tetrahydrate in acetonitrile. The reaction provided 4-[1′-(2″,2″,6″,6″-tetramethyl-1″-piperidinyloxy)-ethyl]phenyl 2,3,4,6-tetra-O-acetyl-β-D -glucopyranoside, glycoconjugated initiator. Star-shaped polystyrene architectures in which glucose was covalently bonded in the core and chain-end were successfully prepared from the glycoconjugated initiator, styrene, and 1,4-divinylbenzene as starting materials. 相似文献
206.
Chunhong Zhang Xiande Shen Ryosuke Sakai Michael Gottschaldt Ulrich S. Schubert Shiho Hirohara Masao Tanihara Shigenobu Yano Makoto Obata Nao Xiao Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2011,49(3):746-753
Metal template synthesis is a useful methodology to make sophisticated macromolecular architectures because of the variety of metal ion coordination. To use metal template methodology, chelating functionalities should be introduced to macromolecules before complexation. In this article, we demonstrate the click‐to‐chelate approach to install chelating functionality to polystyrene (PS) and complexation with Ru(II) ions to form 3‐arm and 4‐arm star‐branched PS Ru(II) complexes. Azide‐terminated PS (PS‐N3) was readily prepared by atom transfer radical polymerization using 1‐bromoethylbenzene as an initiator followed by substitution of bromine by an azide group. The Cu(I)‐catalyzed 1,3‐dipolar cycloaddition of PS‐N3 with 2‐ethynylpyridine or 2,6‐diethynylpyridine affords 2‐(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐tapy) or 2,6‐bis(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐bitapy) ligands bearing one or two PS chains at the first‐position of the triazole rings. Ru(II) complexes of PS‐tapy and PS‐bitapy were prepared by conventional procedure. The number‐averaged molecular weights (Mns) of these complexes were determined to be 6740 and 10,400, respectively, by size exclusion chromatography using PS standards. These Mn values indicated the formation of 3‐arm and 4‐arm star‐branched PS Ru(II) complexes [Ru(PS‐tapy)3](PF6)2 and [Ru(PS‐bitapy)2](PF6)2 on the basis of the Mn values of PS‐tapy (2090) and PS‐bitapy (4970). The structures of these complexes were also confirmed by UV–vis spectroscopy and X‐ray crystallography of the Ru(II) complexes [Ru(Bn‐tapy)3](PF6)2 and [Ru(Bn‐bitapy)2](PF6)2, which bear a benzyl group instead of a PS chain. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
207.
Rui Umeda Toshifumi Jikyo Kazuki Toda Issey Osaka Yutaka Nishiyama 《Tetrahedron letters》2018,59(12):1121-1124
The coupling reactions of allylic and benzylic alcohols and allyltrimethylsilane are efficiently catalyzed by a rhenium complex to give the corresponding 1,5-dienes and alkenes in moderate to good yields. Similarly, alcohols were coupled with ketene silyl acetals to form the corresponding esters. 相似文献
208.
209.
Background
A small heat shock protein AgsA was originally isolated from Salmonella enterica serovar Typhimurium. We previously demonstrated that AgsA was an effective chaperone that could reduce the amount of heat-aggregated proteins in an Escherichia coli rpoH mutant. AgsA appeared to promote survival at lethal temperatures by cooperating with other chaperones in vivo. To investigate the aggregation prevention mechanisms of AgsA, we constructed N- or C-terminal truncated mutants and compared their properties with wild type AgsA. 相似文献210.
Danjo H Hirata K Noda M Uchiyama S Fukui K Kawahata M Azumaya I Yamaguchi K Miyazawa T 《Journal of the American Chemical Society》2010,132(44):15556-15558
Heterobimetallic supramolecular polymers were prepared by treatment of the supramolecular polymers composed of tris(spiroborate) type molecular connecting modules with a potassium cation. On the other hand, the addition of a barium cation led to dissociation of the supramolecular polymer chain. Modulation of polymer formation was realized by the use of small metal cations as a control factor. 相似文献