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21.
Treatment of N-heteroarylacethydrazides with an equimolar amount of nitrous acid afforded N-heteroaryacetylazides and subsequent thermolysis of these azides gave the analogues of 2,3-dihydroimidazo[1,5-a]pyridin-3-one. When some of these cyclized compounds were treated with nitrous acid, the ring opening reaction occurred and recyclized 3-(N-heteroaryl)-1,2,4-oxadiazolin-5-ones were obtained. Treatment of N-heteroarylacethydrazides with two equivalent moles of nitrous acid afforded α-oximino-α-(N-heteroaryl)acetylazides. Thermolysis of these azides gave mixtures of 3-(N-heteroaryl)-1,2,4-oxadiazolin-5-one and 3-hydroxy-4-(N-heteroaryl)furazan. On the basis of the effects of heterocyclic rings and solvents upon the relative yield of two types of the products, one plausible mechanistic explanation for the decomposition of such azides was proposed. α-Oximino-α-(H-heteroaryl)acetylazides were converted into cyano N-heterocycles by the action of alkali in good yields. 相似文献
22.
Applications of mass spectrometry to food proteins and peptides 总被引:3,自引:0,他引:3
The application of mass spectrometry (MS) to large biomolecules has been revolutionized in the past decade with the development of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) techniques. ESI and MALDI permit solvent evaporation and sublimation of large biomolecules into the gaseous phase, respectively. The coupling of ESI or MALDI to an appropriate mass spectrometer has allowed the determination of accurate molecular mass and the detection of chemical modification at high sensitivity (picomole to femtomole). The interface of mass spectrometry hardware with computers and new extended mass spectrometric methods has resulted in the use of MS for protein sequencing, post-translational modifications, protein conformations (native, denatured, folding intermediates), protein folding/unfolding, and protein-protein or protein-ligand interactions. In this review, applications of MS, particularly ESI-MS and MALDI time-of-flight MS, to food proteins and peptides are described. 相似文献
23.
Hatano T Bae AH Sugiyasu K Fujita N Takeuchi M Ikeda A Shinkai S 《Organic & biomolecular chemistry》2003,1(13):2343-2347
It was found that [60]fullerene encapsulated in p-sulfonatocalix[8]arene and single-walled carbon nanotubes (SWNTs) solubilized by sodium dodecylsulfate can be readily deposited on the ITO electrode by electrochemical oxidative polymerization of ethylenedioxythiophene (EDOT) without chemical modification of these carbon clusters. The driving force for the deposition is an electrostatic interaction between the anionic complexes and the cationic charges of poly(EDOT) formed in the oxidative polymerization process. The surface morphology was thoroughly characterized by scanning electron micrograph: the [60]fullerene/poly(EDOT) film is covered by nano-particles with 20-100 nm diameters whereas the SWNTs/poly(EDOT) film is covered by nanorods with several microm length and ca. 100 nm diameter. The results indicate that the anionic complexes act as nuclei for the polymer growth in the oxidation polymerization. Interestingly, when these modified ITO electrodes were photoirradiated, the appearance of a photocurrent wave was observed. The action spectra showed that the photoexcited energy of [60]fullerene or SWNTs is efficiently collected by the electroconductive poly(EDOT) film and transferred to the ITO electrode. 相似文献
24.
The preparation and characterization of a series of niobium(V) complexes that incorporate the linear-linked aryloxide trimers 2,6-bis(4,6-dimethylsalicyl)-4-tert-butylphenol [H3(Me-L)] and 2,6-bis(4-methyl-6-tert-butylsalicyl)-4-tert-butylphenol [H3(tBu-L)] are described. The chloride complex [Nb(Me-L)Cl2]2 (1) was prepared in high yield by reaction of NbCl5 with H3(Me-L) in toluene. In contrast, the analogous reaction with H3(tBu-L) gave a mixture of [Nb(tBu-L)Cl2]2 (2) and [Nb(de-tBu-L)Cl2]2 (3a). During the formation of 3a, one of tert-butyl groups at the ortho position in the tBu-L ligand was lost. When the NbCl5/H3(tBu-L) reaction was carried out in acetonitrile, Nb[H(tBu-L)]Cl3(NCMe) (4) was obtained. Heating a solution of 4 in toluene generated 2 and 3a. The isolated complex 4 underwent ligand redistribution in acetonitrile to produce Nb[H(tBu-L)]2Cl(NCMe) (5). Treatment of NbCl5 with Li3(tBu-L) in toluene afforded 2. The chloride ligands in 1 and 2 smoothly reacted with 4 equiv of MeMgI and LiStBu, resulting in [Nb(R-L)Me2]2 [R = Me (6), tBu (7)] and Nb(Me-L)(StBu)2 (8), respectively. A number of the above complexes have been characterized by X-ray crystallography. In the structures of 1, 2, and 6, the R-L ligand is bound to the metal center with a U-coordination mode, while an alternative S-conformation is adopted for 3a and 8. Complexes 4 and 5 contain a bidentate H(tBu-L) diphenoxide-monophenol ligand. 相似文献
25.
A family of tantalum compounds supported by the triaryloxide [R-L]3− ligands are reported [H3(R-L) = 2,6-bis(4-methyl-6-R-salicyl)-4-tert-butylphenol, where R = Me or tBu]. The reaction of H3[Me-L] with TaCl5 in toluene gave [(Me-L)TaCl2]2 (1). The [tBu-L] analogue [(tBu-L)TaCl2]2 (2) was synthesized via treatment of TaCl5 with Li3[tBu-L]. A THF solution of LiBHEt3 was added to 1 in toluene to provide [(Me-L)TaCl(THF)]2 (3), while treatment of 2 with 2 equiv of LiBHEt3 or potassium in toluene followed by recrystallization from DME resulted in formation of [M(DME)3][{(tBu-L)TaCl}2(μ-Cl)] [M = Li (4a), K (4b)]. When the amount of MBHEt3 (M = Li, Na, K) was increased to 5 equiv, the analogous reactions in toluene afforded [{(bit-tBu-L)Ta}2(μ-H)3M] [M = Li(THF)2 (5a), Na(DME)2 (5b), K(DME)2 (5c)]. During the course of the reaction, the methylene CH activation of the ligand took place. Dissolution of 5a in DME produced [{(bit-tBu-L)Ta}2(μ-H)3Li(DME)2] (6), indicating that the coordinated THF molecules are labile. When the 2/LiBHEt3 reaction was carried out in THF, the ring opening of THF occurred to yield [(tBu-L)Ta(OBun)2]2 (7) along with a trace amount of [Li(THF)4][{(tBu-L)TaCl}2(μ-OBun)] (8). Treatment of 2 with potassium hydride in DME yielded [{(tBu-L)TaCl2K(DME)2}2(μ-OCH2CH2O)] (9), in which the ethane-1,2-diolate ligand arose from partial C-O bond rupture of DME. The X-ray crystal structures of 2, 3, 4, 5a, 6, 7, and 9 are described. 相似文献
26.
Kenjiro Hattori Akira Kenmoku Tsukasa Mizuguchi Daisuke Ikeda Mamoru Mizuno Toshiyuki Inazu 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):9-16
A synthetic series of heptakis-galactose-branched cyclodextrins (termed CDs) having a longer spacer arm using two amino-caproic acids as an enlarging unit were prepared. Starting with heptakis-amino-β-CD or heptakis-amino-caproic-amide-β-CD, treated with galactosyl-glucono-amide-caproic acid, the new compounds heptakis (Gal-cap1)-CD (4) or heptakis (Gal-cap2)-CD (5) were obtained. The longer galactose spacer arm extremely favors the PNA association. The effect of branch length on K with PNA was enhanced up to 138-fold 3 as well as with DXR enhanced up to 81-fold. Hexakis (Gal-cap2)-CD (6) was prepared and the association constants with rat liver cells were observed to be 2.5 × 1010 M−1. A multi-high mannose type oligosaccharide branched CD (7) showed a large association constant with DXR up to 1.1 × 109 M−1. The two-dimensional map for the association constants of newly synthesized oligosaccharide-branched CDs toward lectin or liver cells versus the association constants toward a drug (doxorubicin) suggested a method of finding a better targeting drug carrier. The structural effect of the oligosaccharide-CDs showed that the number and length of the branch were dominant factors in designing for enhanced dual recognition. 相似文献
27.
Methyl and ethyl 2-quinolylacetate were prepared from quinoline 1-oxide via acetoacetie ester derivatives. Methyl 2-quinolyl, 1-isoquinolyl, 6-methoxy-3-pyridazinyl, 4-pyridyl and 2-methyl-4-pyridylacetate were synthesized from the corresponding heterocyclic N-oxides via β-aminoerotonie ester derivatives. 相似文献
28.
The chiral separation of trimetoquinol hydrochloride, which is a bronchodilator (Inolin), and three related compounds by micellar electrokinetic chromatography was investigated using a bile salt as a chiral surfactant. Enantiomers of these compounds, except laudanosoline, were successfully separated within 12 min using a separation tube of effective length 500 mm × 0.05 rum i.d. and a 0.05 M sodium taurodeoxycholate solution of pH 7.0. The observed theoretical plate numbers of the peaks were ca. 150000. Chiral recognition was affected by the structure of bile salts, the pH of the buffer solutions used and the structure of the solutes. Of four kinds of bile salts, successful chiral separation was achieved only using sodium taurodeoxycholate solution under neutral conditions. The method was applied to the optical purity determination of trimetoquinol hydrochloride. The effects of surfactant concentrations and some additives to the micellar solution are briefly described. 相似文献
29.
Miki Murata Hiyoruki Yamasaki Tsukasa Ueta Masayuki Nagata Masanori Ishikura Shinji Watanabe Yuzuru Masuda 《Tetrahedron》2007,63(19):4087-4094
The general and efficient silylation of aryl halides has been developed utilizing triethoxysilane and a rhodium catalyst. The substrate scope is broad and includes ortho-, meta-, and para-substituted electron-rich and -deficient aryl iodides. In addition, the silylation of aryl bromides and fluoroalkanesulfonates proceeded in the presence of tetra-n-butylammonium iodide. 相似文献
30.
2,3-Dihydroimidazo[1,5-α]pyridin-3-one (IV) was obtained by thermolysis of 2-pyridylacetyl azide (II) which was prepared from 2-pyridylacetohydrazide (I) on treatment with an equivalent mole of nitrous acid. Treatment of I with excess nitrous acid yielded α-oximino-α:-(2-pyridyl)-acetylazide (V). Thermal decomposition of V gave 3-(2-pyridyl)-1,2,4-4H-oxadiazolin-5-one (VII). 2-Cyanopyridine (IX) was obtained from V by the action of alkali. 2,3-Dihydroimidazo-[1,5-α ]pyridin-3-one (IV) was rearranged to VII upon treatment with nitrous acid. J. Chem. Soc., 14, 993 (1977) 相似文献