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.

International audienceModern 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

RECHERCHE D'UNE STRUCTURE INTERMEDIAIRE DANS σT ET σe1 DU Ti.

Nous avons mesuré la section efficace totale et la diffusion élastique des neutrons sur le Titane entre 150 keV et 1200 keV. Les résultats obtenus indiquent la présence probable d'un état intermédiaire de J = 1/2 pour des neutrons de 700 keV environ et de largeur Ɖ [MATH] ~ 40 keV et Ɖ [MATH] ~ 25 keV.We have measured the total and elastic cross sections of neutrons on Titanium between 150 keV and 1200 keV. The results shows the presence of an intermediate state of J = 1/2 for an energy neutrons of 700 keV and spreads Ɖ [MATH] ~ 40 keV, Ɖ [MATH] ~ 25 keV

DETERMINATION OF THE ENANTIOMERIC COMPOSITION OF CHIRAL Δ-2-OXAZOLINES-1,3 BY 1 H AND 19 F NMR SPECTROSCOPY USING CHIRAL LANTHANIDE-SHIFT REAGENTS

International audienceThe 300 MHz H NMR spectra of 2-ethyl Δ-oxazoline 1m have been studied in CCl4, CD3CN and C6D6 solutions, in the presence of the achiral lanthanide shift reagent (LSR), tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)-europium III, 4 known as Eu(fod)3, (see Sch. 1).10.1081/SL-120005675-SCH0001Scheme 1. Oxazolines and lanthanides reagents used in this paper.All the protons of 1m were deshielded at various extent, and the sequence observed for their Δδ suggested a major complexation at the basic N(3) center of the heterocycle. Then the chiral monosubstituted oxazoline 1e and the disubstituted oxazolines 1Aa–d and 1Ba, were studied in the presence of chiral LSR, tris-[D, D dicampholylmethanato] europium III Eu(dcm)35 and tris-[3-(heptafluoropropylhydroxy-methylene)-d-camphorato] praseodym III Pr(hfc)36 H NMR, and eventually F[H] NMR spectra were mostly recorded in C6D6 solution. Substantial to very important enantiomeric shift difference ΔΔδ values were observed i/ for proton signals concerning the diastereomeric methyl group with all the oxazolines, for the ortho aryl protons of 1Aa and 1Ac, and i/ for the F[H] signals of the fluorinated oxazolines 1Aa–b and 1Ba.NMR results are discussed from substrate and CLSR structure standpoints.For all tested chiral oxazolines there is at least one possibility to proceed to their enantiomeric discrimination either by H or F NMR using Eu(dcm)3 or Pr(hfc)3 as CLSR

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

International audienceStudies 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

Potential proinsecticides of fluorinated carboxylic acids and β-ethanolamines: IV. Evaluation of the Δ2-oxazoline-1,3 structure by 19F NMR monitoring of the in vitro metabolism in locust tissues

International audienceThe enzymatic effect of locust tissues upon hydrolysis of the fluorinated Δ2-oxazoline-1,3 Ia was elucidated using 19F[1H] NMR monitoring.In a phosphate buffer at pH=7.4 (mean physiological pH of locust tissues), the substrate Ia hydrolyses slowly into the corresponding fluorinated hydroxylamide VIa.If diluted, locust haemolymph (12.5% in phosphate buffer) catalyses slightly this hydrolytic pathway, it overall triggers the unmasking of carboxylate IIIa, corresponding to the expected proinsecticide behaviour of Ia. This behaviour is spectacularly almost the unique reaction observed during in vitro assays in concentrated fat body and mesenteron. Inasmuch as β-hydroxylamide VIa is not hydrolysed into carboxylate IIIa during such conditions, it must be concluded that carboxylate formation exclusively results from hydration and hydrolysis of substrate Ia via the aminoester Va. The formation of this intermediate aminoester is demonstrated by complementary assays. The enzymes supposed to intervene are of the α-chymotrypsine type for the first step (hydration) and of the esterase type for subsequent hydrolysis of intermediate aminoester Va.Thus, this work constitutes the first example of a Δ2-oxazoline-1,3 structure exploited for elaborating proinsecticides of carboxylates III and/or β-ethanolamines II based on enzymatic activation in insects