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151.
Salah Bouhroum Joseph A. Grondin Stephan Houdier Hassan Lazrek Mohamed Rhazi Abdelouahad Tolaimate 《Journal of carbohydrate chemistry》2013,32(3):309-314
ABSTRACT Hydrazine acetate is shown to effect selective deacetylation on peracetylated glycals like D-xylal, D-glucal, D-galactal and L-rhamnal. It is demonstrated that the observed selectivity on the -4 position cannot be explained by acetyl migration during the reaction. 相似文献
152.
Abdul Majid Amber Batool Salah Ud-Din Khan Sajjad Haider 《International journal of quantum chemistry》2019,119(14):e25924
First-principles calculations were performed to investigate the vibrational properties of monomers and dimers of titania, silica, and titania-silica hybrid clusters. Density functional theory-based formulism was employed to optimize the geometry at the B3LYP level and calculate the infrared and Raman spectra of the clusters by using the GGA-PBE exchange-correlation functional. It was found that the vibrational spectra of Ti2O4, Si2O4, and TiSiO4 hybrid clusters provide fingerprint information about structures and structural transitions during the formation of cluster structures. In the case of Si2O4 the mode at 410 cm−1 exhibited the largest vibration of Si atoms, whereas in the case of Ti2O4 the mode at 442 cm−1 exhibited the largest vibration of Ti atoms. The hybrid cluster TiSiO4 was structured using two different methods to explore the effects of starting geometry on the structures and vibrational modes of the clusters. The structural properties of the clusters remained unchanged but vibrational modes were found to be different. It is found that Si shows notable vibrations, but the metal atom Ti merely shows any vibration in the case of TiSiO4 hybrid clusters. The low and intermediate frequency modes were stiffened, whereas the three highest frequency modes were softened when the starting geometry of the hybrid clusters was changed from Si2O4 to Ti2O4. 相似文献
153.
Dudley E Lemiere F Van Dongen W Langridge JI El-Sharkawi S Games DE Esmans EL Newton RP 《Rapid communications in mass spectrometry : RCM》2003,17(11):1132-1136
Modified nucleosides in the urine have been postulated to be diagnostic indices of disease, particularly of cancer. The urine of a patient with terminal head and neck cancer has been found to contain a modified nucleoside with a protonated molecule of m/z 228. By means of high-performance liquid chromatography/ion trap mass spectrometry (HPLC/ITMS) and capillary liquid chromatography/triple quadruple mass spectrometry (CapLC/TQMS) we have identified the compound as 5'-deoxycytidine. This is the first report of 5'-deoxycytidine in man: in addition to the elucidation of its structure, its possible origins and the potential significance of its occurrence are discussed. 相似文献
154.
Mohamed Salah K. Youssef Mohamed S. Abbady Ragaa A. Ahmed Ahmed A. Omar 《Journal of heterocyclic chemistry》2013,50(2):179-187
Ethyl 7‐amino‐3‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐aryl‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxylate was synthesized by the reaction of 4‐(2‐aminothiazol‐4‐yl)‐3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazoline with arylidene ethyl cyanoacetate and it transformed to related fused heterocyclic systems via reaction with various reagents. The biological activities of these compounds were evaluated. 相似文献
155.
Abeer Abas Abd El Aty Naglaa Salah El-Deen Mohamed Ibrahim Ahmed Saleh Ahmed Atef El-Beih Mohamed Helmy Abdelrazik Taha Abdelrahim Hussien Mahmoud Moustafa 《中国化学会会志》2020,67(4):652-657
Due to the rapidly increasing number of pathogenic bacteria, viruses, and tumor cells that possess resistance toward established therapies, lead structures for the development of new drugs are in high demand. The plant material of Tanacetum sinaicum is considered a prolific source of the potent biologically active sesquiterpene Tanacetolide A ( 1 ). In our research, we focused on the structural transformation of the substrate Tanacetolide A (compound 1 ) by suspended culture of the novel locally isolated terrestrial fungus Rhizopus oryzae KX685359. The fungal transformation resulted in the formation of 1β,3α-dihydroxy-6α-hydroperoxy-eudsm-4(15)-ene 12-oic acid ( 2 ) with higher antiproliferative activity against colon cancer cell line (Caco-2) than that of the parent compound ( 1 ). 相似文献
156.
Feriel Necibi Saida Ben Salah Julien Roger Jean-Cyrille Hierso Taoufik Boubaker 《国际化学动力学杂志》2020,52(10):669-680
The kinetics of the reactions of 4-nitrobenzofurazane 1a , 4-nitrobenzothiadiazole 1b , and 4-nitrobenzoselenadiazole 1c with a series of 4-Y-substituted phenoxide anions 2a-e (Y = OMe, Me, H, Cl, and CN) in aqueous solution at 20°C were investigated photometrically. The derived second-order rate constants (k2) have been combined with the nucleophilicity parameters values of these series of anions 2a-e to determine the electrophilicity parameters E of electrophiles 1a-c according to the linear free-energy relationship (log k2)/s versus N. General reactivity of these electrophiles 1a-c is found to be fairly similar with E values ranging in −10.77 ± 0.61 < E < −7.53 ± 0.29. The comparison with structurally related neutral electron-deficient heteroaromatic and aromatic compounds revealed that 1a - c are more reactive than 1,3,5-trinitrobenzene, as benchmark aromatic electrophile used in nucleophilic addition or substitution processes. The rate constants for the reactions of 4-nitrobenzochalcogenadiazoles 1a-c with some other nucleophiles were measured and found to agree with those calculated from Mayr's equation. Finally, analysis of the rate data in terms of the Brønsted approach reveals that 1a-c exhibits especially low intrinsic reactivity in σ-adducts 3 forming reactions. 相似文献
157.
El Dine RS El Halawany AM Nakamura N Ma CM Hattori M 《Chemical & pharmaceutical bulletin》2008,56(5):642-646
Four new lanostane triterpene lactones (colossolactone I, colossolactone II, colossolactone III and colossolactone IV) were isolated from the Vietnamese mushroom Ganoderma colossum (FR.) C. F. BAKER along with five known compounds. The structures of the new compounds were determined on the basis of MS, NMR and circular dichroism. 相似文献
158.
Clay organifier with propylene oxide‐capped polyethylene glycol (PEG) with amine end group (jeffamines ED600–2003) was synthesized through an ion exchange process between sodium cations in montmorillonite (MMT) and ? NH groups in ED600–2003. The d‐spacing of organoclay was found to be 1.697–1.734 nm compared to 0.96 nm of pristine MMT. Transmission electron microscopy (TEM) was used to determine the molecular dispersion of the clay within ED600. Polyurethane‐urea/montmorillonite (PUU‐MMT) nanocomposites were prepared via in situ polymerization from polyethylene glycol (PEG 400) or 1,4 butane diol (1,4 BD), toluene diisocyanate (TDI), jeffamines ED600–2003, and 1–12 wt% of organoclay. Intercalation of PUU into modified clays was confirmed by X‐ray diffraction (XRD), scanning electron microscopy, and TEM. The barrier properties were significantly reduced; however, the thermal stability was increased in the nanocomposites as compared to the pristine polymer. Nanocomposites exhibited optical clarity and solvent resistance. The mechanical properties and the glass transition temperature of PUU were improved with the addition of organoclay. The incorporation of silicate layers gave rise to a considerable increase in the storage modulus (stiffness), demonstrating the reinforcing effect of clay on the PUU matrix. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
159.
Dey SK Mondal N El Fallah MS Vicente R Escuer A Solans X Font-Bardía M Matsushita T Gramlich V Mitra S 《Inorganic chemistry》2004,43(7):2427-2434
Tridentate/tetradentate Schiff base ligands L(1) and L(2), derived from the condensation of o-vanillin or pyridine-2-aldehyde with N,N-dimethylethylenediammine, react with nickel acetate or perchlorate salt and azide, cyanate, or thiocyanate to give rise to a series of dinuclear complexes of formulas [Ni(L(1))(micro(1,1)-N(3))Ni(L(1))(N(3))(OH(2))].H(2)O (1), [[Ni(L(1))(micro(1,1)-NCS)Ni(L(1))(NCS)(OH(2))][Ni(L(1))(micro-CH(3)COO)Ni(L(1))( NCS) (OH(2))]] (2) [[2A][2B]], [Ni(L(1))(micro(1,1)-NCO)Ni(L(1))(NCO)(OH(2))].H(2)O (3), and [Ni(L(2)-OMe)(micro(1,1)-N(3))(N(3))](2) (4), where L(1) = Me(2)N(CH(2))(2)NCHC(6)H(3)(O(-))(OCH(3)) and L(2) = Me(2)N(CH(2))(2)NCHC(6)H(3)N. We have characterized these complexes by analytical, spectroscopic, and variable-temperature magnetic susceptibility measurements. The coordination geometry around all of the Ni(II) centers is a distorted octahedron with bridging azide, thiocyanate/acetate, or cyanate in a micro(1,1) mode and micro(2)-phenolate oxygen ion for 1-3, respectively, or with a double-bridging azide for 4. The magnetic properties of the complexes were studied by magnetic susceptibility (chi(M)) versus temperature measurements. The chi(M) nus T plot reveals that compounds 1 and 4 are strongly ferromagnetically coupled, 3 shows a weak ferromagnetic behavior, and 2 is very weakly antiferromagnetically coupled. 相似文献
160.
The rate of corrosion of copper metal in presence of methyl amine, dimethyl amine, diethyl amine, triethyl amine, diethanol amine, and triethanol amine determined by measuring the anodic limiting current. The factors used are type of organic amine compounds and its concentration, concentration of H3Po4, viscosity of solution, density, diffusion coefficient, and rate of rotation. It has been found that, the rate of corrosion decrease in presence of these compounds. The inhibition percentage ranged from 9.72% to 80.14% depending on the type of inhibitor and its concentration. It is suggested that the decrease in the rate of corrosion is attributed to the increase in interfacial viscosity of the solution and decrease the diffusion coefficient of the copper ion. It has been found that we can apply the Langmuir, Flory-Huggins, and kinetic adsorption isotherms. It has been found that the rate of inhibition is increases in order: methyl amine, dimethyl amine, diethyl amine, triethyl amine, diethanol amine, and triethanol amine. The rate of corrosion depends on the H3Po4 concentration as well as on the electrode height. The limiting current in undivided cells is higher than in divided cells due to the uprising H2 bubbles, which enhances the rate of corrosion. Also, the rate of corrosion was found to increase by increasing the speed of rotating electrode. The dimensionless groups were calculated, and the relation between them was given and the equation given as following: Sh = 0.5046 Re0.7201(Sc)0.33 for methyl amine; Sh = 0.5381 Re0.7157(Sc)0.33 for dimethyl amine; Sh = 0.4887 Re0.7356(Sc)0.33 for diethyl amine; Sh = 0.5167 Re0.7207(Sc)0.33 for triethyl amine; Sh = 0.5373 Re0.7238(Sc)0.33 for diethanol amine; and Sh = 0.4958 Re0.7280(Sc)0.33 for triethanol amine. 相似文献