Synthesis of a serie of novel spiropyrrolidines has been accomplished by regio and stereoselective 1,3-dipolar cycloaddition of N-metalated azomethine ylides, generated in situ from α-iminoesters 1 in the presence of silver acetate and triethylamine, to 3-arylidene-1-phenyl-pyrrolidine-2,5-diones 2. The structure of the spiroadducts 3 was elucidated by 1H and 13C NMR study. The proposed regio and stereochemistry of spiranic compound has been corroborated by single crystal X-ray crystallographic analyses of compound spiro[3-(4-chlorophényl)-5-(méthylphényl)-2-carbomethoxypyrrolidine-4-(N-phénylsuccinimide)]3bh.
S. Haddad, I. Jalloul, S. Boudriga, M. Askri, M. Knorr, Y. Rousselin, M. M. Kubicki
Spiropyrrolidine, 1,3-dipolar cycloaddition, N-metalated azomethine ylides, crystal structure
The angiotensin-converting enzyme (ACE) inhibitor delapril is shown to exist in two conformational isomers, cis and trans, which interconvert around the amide bond. The two conformers were separated by capillary zone electrophoresis (CZE). The experimental conditions, such as buffer parameters (concentration, pH and nature), voltage, temperature and pH of sample solution were optimized. In order to improve selectivity, different organic modifiers were also investigated. The baseline separation of delapril conformers was accomplished within 6.5 min with a buffer consisting of 100 mM ammonium formate with pH of 3; voltage 25 kV; capillary temperature 15°C and sample pH of 1.6 with detection at 214 nm.
A. Ben Amar, M. Abidi, N. Ben Hamida
Angiotensin-converting enzyme inhibitor, delapril, Capillary Zone Electrophoresis, conformer separation
The rate constants for the decomposition of the 2,2-dimethoxy-3-(methylsulfonyl)-5-nitrothiophene Meisenheimer adduct-σ 2 derided from thiophene 1 have been determined in methanol at 20°C. As we will see, the reaction occurs in two distinct stages. In the first, instantaneous formation of an intermediate species 2,H+ (nitronic acid), favoured at low pH. In the second slower stage the adduct-σ 2 is gradually converted into expected thiophene 1.
A. Echaieb, T. Boubaker
Kinetic, adduct-σ, thiophene, nitronic acid
This paper describes the analysis and rates of hydrolysis of N,N-dialkyl carbamate insecticide, Pirimicarb in aqueous media. This work is carried out by reversed phase Liquid Chromatography and UV Spectrophotometry. Pirimicarb was found to be stable towards hydrolysis in buffered solutions in the pH range of 9-12. The N,N-dialkyl carbamates were more stables to alkaline hydrolysis than the N-monoalkyl carbamates. The rates of hydrolysis with different hydroxide ion concentrations, ranging from 0,2M to 1M, (ionic strength µ = 1, T = 40°C) were measured. Pseudo-first order rate constants for alkaline hydrolysis of Pirimicarb were found to be 4,9 10-3 min-1 for [OH-] = 0,2 M and 2,4 10-2 min-1 for [OH-] = 1M. The effect of temperature on the rates of hydrolysis was also investigated. The obtained negative activation entropy ΔS = - 98,096 J mol-1 K-1, indicates a BAc2 hydrolytic mechanism involving the addition of hydroxide ion to the carbonyl group of the carbamate to form a tetrahedral intermediate, followed by decomposition of this intermediate to give the dimethylamine and the 4-hydroxy-2-dimethylamino-5,6-dimethylpyrimidine.
R. Ouertani, A. Gadhgadhi, N. Ben Hamida
Pirimicarb, kinetic, mechanism, HPLC, spectrophotometric UV
The objective of the current study is to develop and validate a reverse-phase HPLC according to the recommendations of International Conference On Harmonization (ICH) for the determination of Zofenopril. The effects of flow, pH, percentage of organic solvent and column temperature on the retention time of Zofenopril are studied by HPLC / DAD. Chromatographic separation was performed on a column of type Prontosil LC18 Knauer (250 mm * 4.6 mm grain size of 5 μm) at 25°C using a diode array detector (DAD) at 205 nm and a mobile phase was composed of acetonitrile-phosphate buffer 10 mM at pH 2.5 (80:20, v/v) delivered at flow 2 mL min-1. The method is linear in a concentration range from 90 to 210 μg mL-1. The correlation coefficients (R2) regression equations are greater than 0.995. The precision of the method is demonstrated by the values of coefficients of variance are less than 2%. No interference from any components of dosage forms or degradation products were observed. The results of the validation, the proposed method is simple, specific, linear, precise, accurate and could be applied to the analysis of commercial tablets « Zofénil » with an excellent recovery.
W. Bouaissi, M. Abidi, N. Ben Hamida
Zofenopril, HPLC/DAD, Validation
The purpose of this study is the analysis of various samples containing ethanol and/or methanol in aqueous solutions presents in bottles provided by National Metrology Institute of South Africa (NMISA) in proficiency testing studies organized by the Intra-African System of Metrology (AFRIMETS). We received two samples, for each one 3 flasks of 25 mL. The flasks were kept, directly after reception and before analysis at 4 ± 1°C. The analysis was performed by GC-FID coupled to a headspace (HS) autosampler with internal standard calibration. The method validation was performed by evaluating the selectivity, linearity, repeatability, accuracy, limits of detection and quantification and specificity, according to the XPT-90-210 standard. The estimation of the measurements uncertainties was successfully realized according to the Guide to the Expression of Uncertainty in Measurement (GUM).
I. Limam, M. Mezni, R. Khrouf, W. Belazrag, M. Ben Achour
Ethanol, HS-GC-FID, Proficiency testing, measurements uncertainties, internal standard
Anion exchange phenomena inside various functional coatings have been investigated by means of impedance measurements. Emphasis is given to the selectivity of anions that would allow the application to ion-selective electrodes based on electrolyte/insulator/semiconductor devices. The selectivity of anion exchange with respect to anion type follows the empirical Hofmeister sorting series. But other parameters are also operating such as the chemical nature of the anionic sites and the possible anion-dependent swelling of the electrode’s coating by the solvent.
H. Touzi, Y. Chevalier, R. Kalfat, N. Jaffrezic-Renault
anion exchange, ion selectivity, impedance measurements
The effects of a mono-algal diet and the starvation trials on the content of the lipid classes and the fatty acid composition of the digestive gland of the scallop Flexopecten glaber were assessed in 2010. Results have shown that starvation induces the mobilization of triacylglycerol into phospholipids in the digestive gland of the scallop F. glaber. Also, food deprivation induced the depletion of energetic fatty acids (14:0, 16:0, 20:5n-3) and the selective retention of essential and structural-type fatty acids (20:4n-6, 22:6n-3, 22:2). A significant increase of the non methylene interrupted dienoic fatty acid (22:2) was noted in the triacylglycerol of specimens exposed to mono-specific-diet based on the micro alga Isochrysis galbana clone Tahitian (T-Iso). This would be explained by the substitution to the 20:5n-3 through de novo synthesis of the 22:2.
K. Telahigue, I. Rabeh, T. Hajji, N. Ghazali, W. Masmoudi, M.S. Romdhane, M. El Cafsi
Digestive gland, Isochrysis galbana, fatty acid, food deprivation, Pectinids
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