排序方式: 共有80条查询结果,搜索用时 15 毫秒
61.
Hitoshi Tamiaki Shizuka MatsunagaYoshichika Taira Ayaka WadaYusuke Kinoshita Michio Kunieda 《Tetrahedron letters》2014
Zinc complexes of methyl 31-demethyl-bacteriopheophorbides-d possessing a 2-(un)substituted ethynyl or ethenyl group at the 20-position were prepared through palladium-catalyzed cross-coupling of their 20-bromide with the corresponding alkyne or alkene. The synthetic zinc 20-substituted 3-hydroxymethyl-131-oxo-chlorins self-aggregated in an aqueous micellar solution to give similar large oligomers as self-aggregates of bacteriochlorophylls in the core part of the main light-harvesting antenna of photosynthetic green bacteria. The zinc 20-ethynyl-chlorin fully gave the self-aggregates, but its 202-substitution disturbed the self-aggregation. The 20-(2-phenyl)ethenyl moieties induced the formation of relatively smaller oligomers as well as residual monomers due to their steric bulkiness. 相似文献
62.
Dr. Ryosuke Ueki Ayaka Ueki Naoto Kanda Prof. Shinsuke Sando 《Angewandte Chemie (International ed. in English)》2016,55(2):579-582
Oligonucleotide‐based hepatocyte growth factor (HGF) mimetics are described. A DNA aptamer to Met, a cognate receptor for HGF, was shown to induce Met activation when used in dimer form. The most potent aptamer dimer, ss‐0, which was composed solely of 100‐mer single‐stranded DNA, exhibited nanomolar potency. Aptamer ss‐0 reproduced HGF‐induced cellular behaviors, including migration and proliferation. The present work sheds light on oligonucleotides as a novel chemical entity for the design of growth factor mimetics. 相似文献
63.
Bathini Madhusree S. Tanabe Ayaka Amaha Öztürk Ryo Tatsukawa Nobuyuki Miyazaki Emin Özdamar Orhan Aral Osman Samsun Bayram Öztürk 《Analytical and bioanalytical chemistry》1997,359(3):244-248
Concentrations of butyltin compounds (BTs) were determined in harbour porpoise (Phocoena phocoena) collected from the Turkish coastal waters of the Black Sea. Total butyltin compounds (∑ BTs) in the liver were in the range
of 89–219 ng/g on a wet weight basis. The dibutyltin (DBT) residues were higher than those of tributyltin (TBT), suggesting
the degradation of TBT to DBT in the liver and the metabolic capacity comparable to other marine mammals. Any sex difference
and age-dependent accumulation of BTs residues were not found in harbour porpoises, but residue levels increased until maturity
and then remained constant. When compared with other marine mammals, the present results indicate that the Black Sea is also
contaminated with butyltin compounds, but to a lesser degree than coastal waters of developed nations. The biomagnification
factor in harbour porpoises was 0.8, which was comparable with pinnipeds and lower than cetaceans.
Received: 23 December 1996 / Revised: 15 April 1997 / Accepted: 16 April 1997 相似文献
64.
Zinc complexes of 3-hydroxymethyl-131-oxo-chlorins possessing a vinyl or its trans-substituted group at the 20-position were prepared through regioselective bromination and successive palladium-catalyzed cross-coupling reactions from naturally occurring chlorophyll-a. The synthetic zinc chlorophyll-a derivatives self-aggregated in an aqueous Triton X-100 micelle solution to give red-shifted and broadened electronic absorption bands, which were similar to those of bacteriochlorophyll-c/d self-aggregates in the main light-harvesting antenna systems of green photosynthetic bacteria. Because of the sterically demanded perpendicular orientation of the (un)substituted ethenyl group to the chlorin π-system, the present model compounds had less J-aggregation ability in a slipped π–π interaction fashion than the corresponding saturated ethyl-type analogs, while halogenations at the terminal of the 20-vinyl group enhanced the ability due to their electron-withdrawing effect. 相似文献
65.
Organocatalytic Enantioselective Decarboxylative Reaction of Malonic Acid Half Thioesters with Cyclic N‐Sulfonyl Ketimines by Using N‐Heteroarenesulfonyl Cinchona Alkaloid Amides 下载免费PDF全文
Prof.Dr. Shuichi Nakamura Masahide Sano Ayaka Toda Dr. Daisuke Nakane Prof.Dr. Hideki Masuda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):3929-3932
The organocatalytic enantioselective decarboxylative Mannich reaction of malonic acid half thioesters (MAHTs) with cyclic N‐sulfonyl ketimines by using N‐heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. The reaction proceeds through a nucleophilic addition of the MAHTs to the ketimines prior to decarboxylation. 相似文献
66.
Chemo‐ and Regioselective Reduction of 5,15‐Diazaporphyrins Providing Antiaromatic Azaporphyrinoids 下载免费PDF全文
Ayaka Yamaji Prof. Dr. Hayato Tsurugi Prof. Dr. Yoshihiro Miyake Prof. Dr. Kazushi Mashima Prof. Dr. Hiroshi Shinokubo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):3956-3961
Reagent‐controlled chemo‐ and regioselective reduction of 5,15‐diazaporphyrins has been developed. The selective reduction of carbon–carbon double bonds of diazaporphyrins provides 18 π aromatic isobacteriochlorin‐type products, whereas the reduction of carbon–nitrogen double bonds leads to selective formation of 20 π N,N′‐dihydrodiazaporphyrins in excellent yields. The distinct antiaromatic character of N,N′‐dihydrodiazaporphyrins has been revealed. The free‐base N,N′‐dihydrodiazaporphyrin exhibits slower inner NH tautomerism than that in the corresponding 18 π porphyrins. 相似文献
67.
68.
69.
A microscopic system for the observation of reactions at a liquid-liquid interface was established, to which strong magnetic fields (0-0.4 T) could be applied with permanent magnets. In situ observation for the interfacial extraction of fluorescent and paramagnetic Eu(III) ion with 2-thenoyltrifluoroacetone (Htta) in dodecane was carried out. In the presence of oxalate (ox2-), micro-aggregates of Eu(III)-tta-ox complexes were generated in the aqueous phase before its extraction. When the micro-aggregates diffused to the dodecane-water interface, Eu(tta)3 was extracted with excess Htta in the dodecane phase. The microextraction process of the aggregates was observed as random flashes of Eu(tta)3 fluorescence at the dodecane-water interface. The single flash contained about 10(-16)-10(-14) mol of Eu(III). An application of magnetic fields made the flash frequency increase, which corresponded to an enhancement of interfacial Eu(III) extraction rate. The enhancement effect was attributable to the magnetophoresis of the paramagnetic microaggregates to the dodecane-water interface. 相似文献
70.
Synthesis of (±)-gallocatechin and (±)-epigallocatechin gallates by electrophilic cycloarylation is reported. The precursors for cyclization were prepared by reagent-controlled stereo-selective opening of epoxide with phenol. Activation of the S-oxidized S,O-acetal enabled electrophilic cycloarylation to stereoselectively provide the acylated catechins. 相似文献