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71.
This paper describes an efficient synthetic route for various types of novel carbocyclic nucleosides. The required stereochemistry of the targeted nucleosides was successfully obtained with use of Grubbs cyclization and Trost allylic alkylation from the carbohydrate chiral template "D-lactose". 相似文献
72.
The characteristic features of ion transmission properties in a radio-frequency (RF) electric-field driven ion funnel using the SIMION ion trajectory simulation package is presented. A user program applying the Douglas ion-neutral collisional drag coefficient model is incorporated to properly account for the ion focusing and transport effect of the background gas under the effect of the driving RF and a superimposed DC field. The simulated m/z transmission window compares favorably with the experimental results reported by Smith et al. RF amplitude and pressure dependence of experimentally observed m/z transmission windows are also examined, and an approximated effective potential model based on Gerlich's equation is proposed to interpret the low-m/z cutoff behavior. A modified ion funnel configuration is described. 相似文献
73.
J. Kučera V. Senft F. H⫲zl L. Soukal 《Journal of Radioanalytical and Nuclear Chemistry》1988,122(2):361-372
Cadmium and zinc levels in urine, serum, hair obtained from workers professionally exposed to cadmium oxide dust and from a control, nonoccupationally exposed group were determined by neutron activation analysis. The study was completed by biochemical monitoring tests such as the 2 (2-MG) determination in urine and serum and the -aminolevulinic acid dehydratase (ALAD) determination in blood. Significantly increased levels of cadmium in urine, serum, and hair, 2-MG in urine and serum, ALAD in blood and decreased levels of zinc in serum were found in the exposed group compared to the control group. The most distinct differences of the parameters studied were observed for cadmium in hair. Correlations among the parameters were preliminary evaluated, too. For quality assurance purposes, the cadmium and zinc concentrations were determined in biological (standard) reference materials NBS SRM-1577 Bovine Liver, Bowen's Kale, IAEA A-11 Milk Powder, and IAEA H-8 Horse Kidney. 相似文献
74.
Reaction of 1,6-enynes with a hydrosilane in the presence of immobilized cobalt/rhodium bimetallic nanoparticles gives 2-methyl-1-silylmethylidene-2-cyclopentanes in the absence of carbon monoxide and 2-formylmethyl-1-silylmethylidene-2-cyclopentanes under 1 atm of carbon monoxide, respectively. [reaction: see text] 相似文献
75.
Jae Hyung Park Yong Woo Cho Yoen Ju Son Kwangmeyung Kim Hesson Chung Seo Young Jeong Kuiwon Choi Chong Rae Park Rang-Woon Park In-San Kim Ick Chan Kwon 《Colloid and polymer science》2006,284(7):763-770
An anthracycline drug, adriamycin, was chemically conjugated onto the backbone of glycol chitosan via an acid-labile cis-aconityl linkage. The physicochemical characteristics of the glycol chitosan–adriamycin (GC–ADR) conjugates were investigated by dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. The GC–ADR conjugates were capable of forming nano-sized self-aggregates in an aqueous medium, when the adriamycin content in the conjugate was in the range of 2.0–5.0 wt.%. The self-aggregates were spherical in shape, and had mean diameters of 238–304 nm, depending on the adriamycin content. The critical aggregation concentrations of the conjugates, estimated by the fluorescence quenching method, were as low as 1.0–2.5×10−2 mg/ml. The size of self-aggregates was not affected by the polymer concentration in the range from 50 to 2,000 μg/ml, and was maintained up to 8 days in phosphate-buffered saline (pH 7.4), indicating high colloidal stability. The release of adriamycin from self-aggregates was significantly dependent on the pH of the medium due to the cis-aconityl linkage; e.g., the amount of adriamycin released for 4 days was 7.3±0.3% at pH 7, whereas it was 29.3±1.9% at pH 4. The cell viability results demonstrated that free adriamycin shows more potent cytotoxicity than the conjugates, primarily attributed to the sustained release of adriamycin from self-aggregates. In conclusion, the self-aggregates, formed by GC–ADR conjugates, might be useful for the site-specific delivery of adriamycin in a sustained manner. 相似文献
76.
Tae?Shin?Chung Young?Mee?Na Shin?Won?Kang Ok-Sang?JungEmail author Young-A?Lee 《Transition Metal Chemistry》2005,30(5):541-545
Hydrogen peroxide oxidation of platinum(II) compounds containing labile groups such as Cl, OH, and alkene moieties has been carried out and the products characterized. The reactions of [PtII (X)2 (N–N)] (X = Cl, OH, X2 = isopropylidenemalorate (ipm); N–N 2,2-dimethyl-1,3-propanediamine [(dmpda), N-isopropyl-1,3-propanediamine (ippda)] with hydrogen peroxide in an appropriate solvent at room temperature affords [PtIV (OH)(Y)(X)2(N–N)] (Y = OH, OCH3). The crystal structures of [PtIV(OH)(OCH3)(Cl)2(dmpda)]·2H2O (P-1 bar, a = 6.339(2) Å , b = 9.861(1) Å, c = 11.561(1) Å, a = 92.078(9)°, β = 104.78(1)°, γ=100.54(1)°, V = 684.3(2) Å3, Z = 2R = 0.0503) and [PtIV(OH)2(ipm)(ippda)]·3H2O (C 2/c, a = 27.275(6) Å, b=6.954(2) Å, c = 22.331(4) Å, β = 118.30(2)°, V = 3729(2) Å3, Z = 8, R = 0.0345) have been solved and refined. The local geometry around the platinum(IV) atom approximates to a typical octahedral arrangement with two added groups (OH and OCH3; OH and OH) in a transposition. The platinum(IV) compounds with potential labile moieties may be important intermediate species for further reactions. 相似文献
77.
Young-Gu Cho Dae-Kwang Park Dae-Won Park Hee-Chul Woo Jong-Shik Chung 《Research on Chemical Intermediates》2002,28(5):419-431
The selective oxidation of hydrogen sulfide containing excess water and ammonia was studied over vanadium-bismuth mixed oxide catalysts. The investigation was focused on understanding the complex reaction steps and the roles of each metal oxide. Therefore, supported V2O5/TiO2, V-Bi-O/TiO2 catalysts and a mechanical mixture of V2O5 + Bi2O3 were tested in the reaction. Ammonia reacted either with H2S or SO2, produced from the oxidation of H2S. Water vapor promoted the reaction of ammonia and SO2. Strong synergistic phenomena in catalytic activity were observed for the mechanically mixed catalyst of V2O5 and Bi2O3. V-Bi-O/TiO2 catalyst showed very high H2S conversion without any considerable emission of SO2. Temperature-programmed studies (TPR and TPO), XRD and Raman analyses revealed that the high catalytic performance of V-BiO/TiO2 catalyst originated from the high redox capacity of the bismuth vanadate phase. 相似文献
78.
Klapars A Waldman JH Campos KR Jensen MS McLaughlin M Chung JY Cvetovich RJ Chen CY 《The Journal of organic chemistry》2005,70(24):10186-10189
[reaction: see text] A mild and transition-metal-free method for the alpha-arylation of aliphatic nitriles with activated heteroaryl halides was developed using NaHMDS or KHMDS as base at ambient temperature. The key to the success of this method is generation of the nitrile anion in the presence of the heteroaryl halide. The method is applicable to both primary and secondary carbonitriles and a wide range of heteroaryl halides. Selective monoarylation was observed with primary carbonitriles. The operational simplicity and the mild reaction conditions add to the value of this method as a practical alternative to the preparation of alpha-heteroaryl carbonitriles. 相似文献
79.
A. Paulenová P. Rajec M. Ježíková J. Kučera 《Journal of Radioanalytical and Nuclear Chemistry》1996,211(1):145-152
The preconcentration of cadmium from aqueous colloid solution containing 8-hydroxyquinoline as extractant, laurylsulphate natrium as surfactant,n-butanol as co-surfactant was performed using micellar ultrafiltration technique. Filters with different pore size and materials were used to achieve a separation from liquid solutions. The cadmium recoveries depending on different conditions (pH, concentration of surfactant) were determined and the results are explained in the terms of colloidal parameters in the compare with the classical solvent extraction. 相似文献
80.
A three-step one-pot synthesis of fenestranes from a readily available enyne and an alkyne diester has been carried out with cobalt nanoparticles and palladium(II) as catalysts. 相似文献