Biomedical subjects

M Beaufour

Publications and source records attributed to M Beaufour.

10 recordsLinked to original sources

PubMed2003

Determination of the enantiomeric composition of chiral delta-2-oxazolines-1,3 by 1H and 19F NMR spectroscopy using chiral solvating agents.

Studies of the perturbing effect of chiral solvating agents (CSAs) 5a and mostly of 5c upon the NMR spectra of chiral Delta(2)-oxazoline 1 demonstrated the ability of these fluoroalcohols to afford diastereomeric solvates from these solutes. Thus, for all tested Delta(2)-oxazolines 1Aa-d, 1Ba, and 1e there is at least one possibility to proceed to their enantiomeric discrimination either by (1)H or (19)F NMR using these CSAs (see Fig. 1). NMR results are discussed from substrate and CSA structure standpoints and a solvation model is proposed on the basis of the inequivalence senses generally observed. Then the method was applied to extracts of incubated locust tissues obtained by solid phase extraction (SPE) after a partial unmasking of the substrate 1.

Animals↗

PubMed2001

Delta(2)-oxazolines-1,3 and N-acylaziridines as potential proinsecticides of carboxylic acids. V. Direct thin-layer chromatography monitoring of the metabolism in locust tissues.

Modern thin-layer chromatography (TLC) was used for the evaluation of delta2-oxazolines-1,3 I and N-acylaziridine VII structures, as potential proinsecticides of carboxylic acids III. Thus the unmasking2 of the active principles III from delta2-oxazolines-1,3 Ia-c and N-acylaziridine VIIc was monitored by spotting aliquots directly onto RP-18 TLC plates, without any sample pretreatment during in vitro assays performed in concentrated locust tissues. To achieve a good separation of carboxylate IIIa from endogenous components of the tissues, a short preliminary development with methanol or ion-pairing was necessary. From UV-TLC chromatograms (densitograms) it appeared that in a phosphate buffer at pH 7.4, the oxazoline Ia with a C2 substituent devoid of alpha-ramification or alpha,beta-insaturation hydrolysed slowly into the corresponding beta-hydroxylamide VIa and intermediate aminoester Va. Significantly, locust mesenteron (or fat body) efficiently triggered the unmasking of IIIa, a transformation which corresponds to the expected proinsecticide behavior of Ia. Conducting TLC monitoring in the same locust tissues also revealed that the oxazolines Ib and Ic with an alpha-ramification and an alpha,beta-insaturation, respectively, cannot be considered as proinsecticides of the corresponding carboxylic acids IIIb and IIIc. In contrast, the N-acylaziridine VIIc appeared as a convenient proinsecticide structure for masking the carboxylic acid IIIc.

Animals↗

PubMed1987