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151.
Kobayashi S Miyamura H Akiyama R Ishida T 《Journal of the American Chemical Society》2005,127(25):9251-9254
A novel, highly active immobilized ruthenium catalyst, which can be successfully used in oxidation of alcohols to aldehydes and ketones, has been developed. In contrast to most immobilized catalysts, the Ru catalyst has activity that is higher than that of the original non-immobilized catalyst. In a batch system, the Ru catalyst was recovered and reused several times without loss of activity. The catalyst was also applied to a flow system, in which excellent conversions and yields were demonstrated. No leaching of Ru was observed in both cases. 相似文献
152.
The reaction of glycine with NBD-F (4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole) is investigated to establish conditions that provide a high formation rate of NBD-glycine and a low hydrolysis rate of the reagent. The reaction rate increases with higher temperature, larger contents of organic solvent and a sodium borate buffer. The use of borate buffer decreases ther ate of hydrolysis of the reagent. For low-molecular-weight amines, condition for a suitable liquid chromatographic postcolumn reactor include a high content of acetonitrile and 0.1 M sodium borate (pH 8.0–8.5). For proteins, separated by molecular-exclusion chromatography, water is needed for sensitive reactions. Suitable postcolumn reactor conditions include borate buffer (pH 7.9) containing 0.1 M potassium chloride, a 0.02% (w/v) NBD-F solution in acetonitrile with reaction at 50°C for about 45 s. The detection limits for human serum albumin, β-lactoglobulin and myoglobin are 6.6 pmol, 8.4 pmol and 11 pmol, respectively. 相似文献
153.
Muranaka A Okuda M Kobayashi N Somers K Ceulemans A 《Journal of the American Chemical Society》2004,126(14):4596-4604
Oxo-titanium phthalocyanine (TiOPc) derivatives of catechin and hematoxylin (natural ortho-diol type chiral compounds) have been prepared and characterized by spectral and chromatographic techniques. It is demonstrated that the TiOPc unit is an excellent template for chiral recognition through its isolated Q-transitions. The formation of a helical dimeric complex with hematoxylin induces strong CD-activity in the Q-band region. Ab initio geometry optimizations were combined with a Kuhn-Kirkwood coupled-oscillator mechanism to obtain the absolute configuration of hematoxylin. In addition, it is shown that the described chiroptical recognition method is sensitive to slight conformational changes. 相似文献
154.
Kobayashi J Sekiguchi M Shimamoto S Shigemori H Ishiyama H Ohsaki A 《The Journal of organic chemistry》2002,67(18):6449-6455
Three novel quaternary indole alkaloids with an unprecedented 1-azoniatricyclo[4.3.3.0(1,5)]undecane moiety, subincanadines A-C (1-3), as well as two new indole alkaloids with a 1-azabicyclo[5.2.2]undecane moiety, subincanadines D (4) and E (5), and a new indole alkaloid with a 1-azabicyclo[4.3.1]decane moiety, subincanadine F (6), have been isolated from the barks of Aspidosperma subincanum Mart, and the structures of 1-6 and the stereochemistry of 1-3 were elucidated by spectroscopic data and chemical means. 相似文献
155.
Yuan L Feng W Yamato K Sanford AR Xu D Guo H Gong B 《Journal of the American Chemical Society》2004,126(36):11120-11121
Highly efficient, one-step macrocyclizations leading to the formation of macrocyclic hexa(aramides) in high yields (69-82%) are described. The one-step macrocyclizations were facilitated by the preorganization or folding of the backbones of uncyclized precursors in the course of macrocyclization. The preorganization of backbones was achieved by the presence of localized three-centered hydrogen bonds that were adopted in the design of a class of closely related, backbone-rigidified foldamers. The macrocyclization involved reactions between diacid chloride 1 and diamine 2. The crude reaction mixtures and products were conveniently examined by mass spectrometric method (MALDI-TOF). Compared to most traditional one-step macrocyclizations that usually require high dilution conditions and often lead to very low overall yields of the desired products, cyclic hexamers 3 were obtained as the overwhelmingly major product under a variety of reaction conditions, suggesting the generality of this approach. 相似文献
156.
Hiroyuki Hayakawa Hiromichi Tanaka Keiko Sasaki Kazuhiro Haraguchi Takafumi Saitoh Fumi Takai Tadashi Miyasaka 《Journal of heterocyclic chemistry》1989,26(1):189-192
Several 8-substituted cordycepins were prepared via LDA lithiation of 2′,5′-bis-O-(t-butyldimethylsilyl)-cordycepin and successive reactions of its C-8 lithiated species with various types of electrophiles. Wittig reaction of the 8-formyl derivative was also examined. 相似文献
157.
The stereoselective synthesis of the two segments 3 and 4 of macrolactin A 1 is described. Macrolactin A is a 24-membered polyene macrolide antibiotic, which is of interest due to a strong activity against B16-F10 murine tumor cell and HIV-1 virus. The key step of the synthesis is the 1,2-migration reaction of a (diene)Fe(CO)3 complex with a introduction of the thiol group to construct the unstable (E,Z)-conjugated dienic moiety (C8-C11). 相似文献
158.
We have previously established a rapid catechol-O-methyltransferase (COMT) assay using norepinephrine (NE) as a natural substrate and flow-injection analysis. In this study, the method is improved for screening of COMT inhibitors or activators using reversed-phase high-performance liquid chromatographic separation with fluorescence detection. The excess substrate, NE, was removed by the addition of borate in the eluent for HPLC to make an ionic complex with NE, which was eluted faster than the enzymatic product, normetanephrine. The method had good precision and accuracy, and was able to assay one sample in 5 min, showing the usability for screening of COMT inhibitors or activators. 相似文献
159.
A novel synthetic basic resolving agent, cis-1-aminobenz[f]indan-2-ol (ABI), was rationally designed by introducing effective CH/pi interaction sites to cis-1-aminoindan-2-ol (AI), whose chiral recognition ability has been reported from our laboratory. ABI was applicable to a wide variety of racemic arylalkanoic acids and showed moderate to excellent chiral recognition ability, which was obviously higher than that of AI. The fundamental and important role of CH/pi interactions, such as tunable CH(sp(2))/pi and CH(sp(3))/pi interactions, in the chiral recognition by ABI was revealed by X-ray crystallographic study. 相似文献
160.
Aoki S Ye Y Higuchi K Takashima A Tanaka Y Kitagawa I Kobayashi M 《Chemical & pharmaceutical bulletin》2001,49(10):1372-1374
Two novel aplysinopsin-type indole alkaloids, 1 and 2, and three known indole alkaloids were isolated from the marine sponge Hyrtios erecta. These compounds exhibited selective inhibitory activity against the neuronal isozyme of nitric oxide synthase (nNOS). Furthermore, new quinolone 7 was also isolated from the same marine sponge. The chemical structures of these new compounds were elucidated on the basis of spectroscopic analysis. 相似文献