Synthesis of pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines

Starting from 1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones, a synthesis pathway to the tricyclic pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines is described. Reaction of 1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-ones with phosphoryl chloride afforded the corresponding 4-chloro-1H-pyrazolo[3,4-d]pyrimidines. Treatment of these compounds with hydrazine hydrate at reflux temperature gave the hydrazino derivatives, which were subsequently cyclized to the titled compounds on heating with orthoesters in ethanol.     

A Simple Stability Indicating CZE Method for the Analysis of Octreotide Acetate

A simple stability indicating capillary zone electrophoretic method was developed and validated for the analysis of octreotide acetate (OCT-Ac). The best separation was achieved by bare fused silica capillaries (50 μm i.d.; 65.5 cm total and 57.0 cm effective length), phosphate buffer (pH = 3.25; 50 mM), at 32.5 °C. The samples were injected using 50 mbar for 5 s and subjected to the applied voltage of 27.5 kV for separation. The detection was carried out using a PAD at a wavelength of 195 nm. For improving the repeatability of the method, l-histidine was applied as an internal standard. According to the validation results, the method was linear in the concentration range of 3.30–400 μg mL^?1 (correlation coefficient of 0.9996) with a limit of detection of 1.08 μg mL^?1 and a limit of quantification of 3.30 μg mL^?1; accuracy of the method was between 100.4 ± 0.2 and 101.1 ± 0.2 %; intra-assay precision was 0.5–2.6 % and intermediate precision was 1.3–3.2 %. The proposed method was successfully applied for the quantification of OCT-Ac in both a pharmaceutical formulation and force-degraded samples and for the detection and separation of degradation products; besides, the obtained results were used for the evaluation of the degradation kinetics of OCT-Ac under different stress conditions. So, it is concluded that the developed method could be employed as a simple, accurate and precise stability-indicating method in quality control laboratories to assess the quantity and stability of OCT-Ac pharmaceutical products.     

Phosphomolybdic acid supported on Schiff base functionalized graphene oxide nanosheets: Preparation,characterization, and first catalytic application in the multi‐component synthesis of tetrahydrobenzo[a]xanthene‐11‐ones

New Schiff base (SB) functionalized graphene oxide (GO) nanosheets containing phosphomolybdic counter‐anion H₂PMo₁₂O₄₀^¯ (H₂PMo) were successfully prepared by grafting of 3‐aminopropyltriethoxysilane (APTS) on GO nanosheets followed by condensation with benzil and finally reaction with phosphomolybdic acid (H₃PMo₁₂O₄₀, denoted as H₃PMo) and characterized using Fourier transform infrared (FT‐IR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), particle size distribution, energy‐dispersive X‐ray (EDX) analysis, EDX elemental mapping, and inductively coupled plasma optical emission spectrometry (ICP‐OES). The prepared new nanomaterial, denoted as GO‐SB‐H₂PMo, was shown to be an efficient heterogeneous catalyst in one‐pot, three‐component reaction of β‐naphthol, aldehydes, and dimedone, giving high yields of tetrahydrobenzo[a]xanthene‐11‐ones within short reaction times. The catalyst is readily recovered by simple filtration and can be recycled and reused several times with no significant loss of catalytic activity.     

Synthesis of cobalt-based magnetic nanocrystals from cobalt(II) heterocyclic amine complexes

Research on Chemical Intermediates - Cobalt nanocrystals with different morphologies and magnetic properties were prepared from three cobalt(II) heterocyclic amine precursors in alcoholic solution...     

Ultrasonic assisted SPME coupled with GC and GC-MS using pencil lead as a fiber for monitoring the organic volatile impurities of ceftazidime

A simple, rapid, non-destructive, and in-situ method for the isolation and sampling of organic volatile impurities in Ceftazidime is developed using solid-phase microextraction (SPME). For the monitoring of the extracted compounds, gas chromatography (GC) and GC-mass spectrometry analyses are used. The effective factors such as nature of the fiber, SPME mode, extraction temperature, and ultrasonic assistance have been investigated and detailed here. Qualification studies reveal the existence of pyridine (as a degradation product of ceftazidime) and the residual solvents; acetone, methylene-chloride, and diethylamine are the main impurities in the studied pharmaceutical. External standard method is used for quantitative analysis. The % relative standard deviation values are below 10%, and the limits of detection for the detected solvents are 1.06, 0.98, 0.83, and 0.51 ppm, respectively. The proposed method is both accurate and linear and could be used in quality control of ceftazidime and also its stability investigations.     

The helical melamine–Keggin hybrid nanorods: syntheses and characterizations with two strategies,one-step solid-state chemical reaction and experimental solvent diffusion method

Two new Melamine-Keggin hybrid nanorods, MELH-PMo₁₂ and MELH-PW₁₂, for the first time are successfully synthesized by two chemical methods, one-step solid-state chemical reaction method and experimental solvent diffusion method at room temperature. One-step solid-state reactions involve grounded nanorod materials along with grinding of row material and with solvent diffusion method these nanorods synthesized in single crystals form. These compounds crystallized in trigonal space groups P-3. Elemental analysis, infrared spectroscopy, UV spectroscopy and XRD analysis results prove that the samples still possess Keggin type structure. Transmittance electron microscopy and single-crystal X-ray have shown that the samples have nanorod structures.     

Correct derivation of a combined version of the Jouyban–Acree and van’t Hoff model and some comments on ‘Determination and correlation of the solubility of myricetin in ethanol and water mixtures from 288.15 to 323.15 K’

The experimental data reported in the paper by Cai and co-workers [DOI: 10.1080/00319104.2016.1163560] pertaining to the solubility of myricetin dissolved in binary aqueous–ethanol solvent mixtures has been reanalysed. A correct mathematical derivation is provided for the correlation expression from a combination of the van’t Hoff and Jouyban–Acree models. Cai et al. who used the expression in their study, however, erroneously implied that the expression resulted from a simple transformation of the Jouyban–Acree model. No mention was made that one needed to assume a van’t Hoff-type mathematical representation for how the solute solubility varied with temperature in the two mixture co-solvents.     

The potential of the capillary electrophoresis techniques for quality control of biopharmaceuticals—A review

CE is considered as a powerful technique in biopharmaceutical industry, owing to its inherent advantages such as high resolution, efficient separation, and its flexibility to couple with high‐sensitive detecting methods. Present review provides a summary of the applications of CE‐based methods in the quality control of biopharmaceuticals according to the papers published between 1994 and July 2014. This article is divided into the sections based on different CE modes applied in the analysis of biopharmaceuticals and gives detailed information about the employed experimental conditions. At the end some overall conclusions and perspectives are given.     

Br?nsted-acidic ionic liquid [HO3S(CH2)4MIM][HSO4] as efficient and reusable catalyst for one-pot synthesis of β-acetamido ketones

Abstract  

Efficient and convenient synthesis of β-acetamido ketones has been achieved by one-pot reaction of acetophenone, aryl aldehydes, acetyl chloride, and acetonitrile in the presence of 3-methyl-1-(4-sulfonylbutyl)imidazolium hydrogensulfate [HO₃S(CH₂)₄MIM][HSO₄], a Br?nsted-acidic ionic liquid, as a green and reusable catalyst in solvent-free media at room temperature. The catalyst could be recycled and reused without noticeable decrease in catalytic activity.