Synthèse et étude structurale de dérivés substitués en -2 du thiazolidine carboxylate d'éthyle-4 (R)

Pharmacological properties of thiazolidine derivatives are of great interest. For this purpose we prepared two series: 2-hydroxyalkyl-4-carbethoxythiazolidines and 2-carbalkoxyalkyl-4-carbethoxythiazolidines. Their syntheses involve a condensation reaction between L-carbethoxy-cystein and several α-hydroxyketones or β-ketoesters. Compounds 4 and 5 was obtained as an unequal mixture of diastereoisomers. Protons nmr spectra at 300 MHz in the presence of trifluoroacetic acid shows a modification of diastereoisomer percentages which indicate the existence of an equilibrium through an imminium ion intermediate. Therefore, the stereoselectivity observed reflects the relative stability of the different diastereoisomers.     

Handiski simulator performance under PSO-based washout and control parameters optimization

Nonlinear Dynamics - The transfer of advanced technology to the person with a disability who wishes to practice a sporting activity is gaining momentum in the science/engineering world. This paper...     

Simple and fast quantification of nitisone (NTBC) using liquid chromatography-tandem mass spectrometry method in plasma of tyrosinemia type 1 patients

Tyrosinemia type 1, which is caused by a deficiency in fumarylacetoacetate hydrolase, is successfully treatable with nitisone (NTBC), an inhibitor of 4-hydroxyphenyl pyruvate dioxygenase. The recommended average dose of NTBC is 1 mg/kg per day. A rapid liquid chromatography (LC) coupled with negative electrospray ionization tandem mass spectrometry method was developed and validated for the quantification of NTBC in heparinized human plasma. The plasma samples were prepared by precipitation in acetonitrile. NTBC and the internal standard (IS) were chromatographed on a BEH C18 column. Gradient elution was done with a mixture of 10 mM ammonium acetate and methanol. The analyte was analyzed by LC-tandem mass spectrometry with only 2 min run time. Selected reaction monitoring modes for detection of NTBC and the IS were achieved by using m/z 328 > 281 and 234 > 190, respectively. The LC retention times for NTBC and IS were 0.99 and 0.93 min, respectively. The method was linear in the concentration range of 0.75-150 μM with r ≥ 0.998. Thus, this method is suitable for follow-up of patients treated with NTBC, because the current therapeutical concentrations range from 20 to 120 μM.     

Sloshing behavior of a magnetic fluid in a cylindrical container

 Sloshing of a magnetic fluid in a laterally vibrated cylindrical container subject to a non-uniform vertical magnetic field was examined. Internal velocity profiles were measured using ultrasound Doppler velocimetry. The effect of the magnetic field on the resonant frequency of the fluid–container system was examined and the results were compared with theoretical results. The second and third peaks of the power spectra of velocity shifted to lower frequencies as the magnetic field was increased. It was observed that these derived frequency peaks were connected with swirling in the cylindrical container. Received: 9 May 2000 / Accepted: 29 May 2001 Published online: 29 November 2001     

Mecanisme de l'homologation directe d'acetyleniques en allenes

Homologation of a terminal acetylene to an allene is easily accomplished in a “one-flask” process, via a Mannich base which is transformed to the desired allene by a 1–5 hydrogen shift.     

NH<Subscript>3</Subscript>(CH<Subscript>2</Subscript>)<Subscript>5</Subscript>NH<Subscript>3</Subscript>BiCl<Subscript>5</Subscript>: an efficient and recyclable catalyst for the synthesis of benzoxazole,benzimidazole and benzothiazole heterocycles

In this work, the condensation of aromatic aldehydes with different two-substituted aniline catalyzed by NH₃(CH₂)₅NH₃BiCl₅ as heterogeneous and recyclable catalyst was reported. It was demonstrated that NH₃(CH₂)₅NH₃BiCl₅ can act as an efficient and active catalyst and is reusable for six runs without a significant loss of their catalytic activity. Simple preparation of the catalyst, high catalytic activity and good reusability are noteworthy advantages of this catalytic system in the synthesis of benzoxazole, benzimidazole and benzothiazole heterocycles at room temperature under solvent-free conditions.     

On the performance of Fe-Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3: the influence of preparation method

Research on Chemical Intermediates - The selective catalytic reduction of NO with ammonia (NH3-SCR) in the presence of H2O was studied over a series of Fe-Cu-ZSM-5 catalysts prepared by solid-state...