Pierre Babin

The estrogenic activity of certain phytoestrogens in the siberian sturgeon Acipenser baeri

Various phytoestrogens such as formononetin, daidzein, genistein and equol were synthesized. Their purity was assessed by various analytical techniques including melting point determination, thin-layer chromatography (TLC), infra-red spectra (i.r. spectra), nuclear magnetic resonance (1H- and 13C-NMR) and gas chromatography coupled with mass spectrometry (GC-MS). The estrogenic activity of these compounds, as well as biochanin A and coumestrol, was biologically tested by the induction of vitellogenin secretion in yearling sturgeon and compared to the activity of estradiol-17 beta. Pure daidzein, biochanin A, genistein, equol and coumestrol all had estrogenic activity as assessed by their induction of hepatic synthesis of vitellogenin when administrated intraperitoneally to yearling Siberian sturgeon. Coumestrol seemed to be the most potent compound, inducing the most vitellogenin secretion with the lowest dose administered. Formononetin was inactive when administered by the intraperitoneal route. All the phytoestrogens tested were considerably less potent than estradiol-17 beta.

Enzyme immunoassay for 11-ketotestosterone using acetylcholinesterase as laberl: application to the measurement of 11-ketotestosterone in plasma of Siberian sturgeon

A competitive enzyme immunoassay using 11-ketotestosterone (11-KT) covalently coupled to acetylcholinesterase (AChE) from electric eel is developed. Ninety-six well microtiter plates are coated with pure mouse-anti-rabbit-IgG monoclonal antibody and competition is performed in one-step reaction by adding successively 11-KT standard or samples, enzymatic tracer and 11-KT-specific antiserum. This assay is more sensitive (detection limit is 7 pg/ml) than radioimmunoassays previously described, and specificity was not modified by the use of enzymatic tracer. This assay can be performed in less than 5 hr. Validation of the EIA was achieved in a fish model, Siberian sturgeon (Acipenser baeri), by comparative determinations of 11-KT levels in plasma extracts using EIA and RIA. Application to the measurement of 11-KT in plasma of farmed Siberian sturgeon during the first reproductive cycle is reported.

Fonctionnalisation régiosélective en position 2 de benzènes 1,3-disubstitués

Abstract Functionalisation in 2 position of benzenes 1,3-disubstituted by para -directing groups has been investigated, involving 2-trimethylsilylated intermediates when the classical methods (particularly these involving the anion in 2 position) are ineffective. Thus 2-trimethylsilyl derivatives of 1,3-dihalo- or 1,3-dimethoxybenzene have been prepared in good yields. Their conversion into the corresponding 1,2,3-trisubstituted benzenes has been conveniently performed upon acetylation, iodination or sulfonation, except in the case of the sulfonation of the 1,3-dimethoxylated compound in which the ipso effect of the silyl group is surpassed by the directing effect of the methoxy substituents. In contrast, whith the same substrate, cyanation in position 2 was successfully carried out using chlorosulfonyl isocyanate: to our knowledge this reaction is the first example of substitution of a trimethylsilyl by a cyano group in the aromatic series.

Surprising Structural Lability of a Cysteine‐S‐Conjugate Precursor of 4‐Methyl‐4‐sulfanylpentan‐2‐one, a Varietal Aroma in Wine of Vitis vinifera L. cv. Sauvignon Blanc

4‐Methyl‐4‐sulfanylpentan‐2‐one (1; 4MSP) provides a characteristic aroma compound of wines made from Vitis vinifera L. cv. Sauvignon blanc. 4MSP has a strong box‐tree odor with a very low perception threshold and is derived from the cysteinylated precursor S‐(1,1‐dimethyl‐3‐oxobutyl)cysteine (4; P‐4MSP). P‐4MSP is transformed into 4MSP during alcoholic fermentation and is an excellent marker of varietal aroma potential. An improved synthesis of P‐4MSP as well as of its deuterium‐labeled analogue [D6]‐P‐4MSP is described. Several analytical methods (NMR, IR, LSI‐MS, GC/MS, ESI‐MSn) were combined to elucidate spontaneous reversible structural changes of P‐4MSP at different pH values. At low pH, P‐4MSP has a linear keto form. The keto–enol tautomerism was observed at neutral pH. At pH 8, the formation of N‐substituted intramolecular hemiaminal was characterized by ESI‐MS and ESI‐MSn experiments. The hemiaminal loses H2O at high pH to produce a cycloimine, which is easily opened by acid hydrolysis. The keto–enol tautomerism explained the incorporation of only six D‐atoms during the preparation of the P‐4MSP deuterated standard even if [D10]mesityl oxide was used. Derivatization conditions for GC/MS analysis strongly affected the ratio of the monosilylated intramolecular cyclic form and the disilylated linear form of P‐4MSP. The structural changes of P‐4MSP may have a considerable impact on the development of methods of measuring varietal aroma potential.

A convenient approach to perfluorinated organosilicons. Preparation of a fluorinated polysiloxane precursor

Abstract Addition of perfluorooctyl iodide to the double bonds of vinyltrimethylsilane and 1,3-divinyltetramethyldisiloxane, followed by a reduction of the carbon-iodide bond, gives the corresponding C 8 F 17 CH 2 CH 2 Si moicty. Following this approach, |C 8 F 17 CH 2 CH 2 Si(Me)O| 4 . a precursor of highly fluorinated silicones. was conveniently prepared. without using hydrosilylation or Grignard reaction.

A New Practical Preparation of bis(Trimethylsilyl) Peroxide

Abstract Bis(trimethylsilyl) peroxide can be readily obtained by reaction of trimethylchlorosilane with the hexamethylenetetramine-hydrogene peroxide complex.

Synthesis of haptens and conjugates for ELISA of glycitein: development and validation of an immunological test.

Two carboxylic acid haptens of glycitein were synthesized, with a spacer arm at the C2 position. They differed in the length of the spacer arm, with the length of the spacer arms being three or four carbon atoms, and were named Delta3-glycitein and Delta4-glycitein haptens, respectively. The different haptens were coupled to bovine serum albumin (BSA), and the coupling efficiency was assessed by MALDI mass spectrometry. Polyclonal antibodies were generated against the BSA conjugates. An additional conjugate of Delta4-glycitein hapten was generated with swine thyroglobulin (Thyr). Enzyme-linked immunosorbent assays (ELISAs) based on the competition between free glycitein and Delta4-glycitein-Thyr conjugates for specific antibodies were developed. The IC50 of the standard curves was 15.6 ng mL(-1) with anti-Delta3-glycitein and 62.5 ng mL(-1) with anti-Delta4-glycitein, that is, 10.9 and 44 pmol/well, respectively. With the Delta3-glycitein antibody, interassay and intra-assay variations were 12.2 and 11.5%, respectively. Specificity tests did not show any significant cross-reaction with any other soy isoflavone. This specificity is not influenced by the length of the spacer arm. The assay was validated by measurements performed on plasma samples as well as on soy-based foodstuffs and on soy-based food supplements.

Synthèse d'aryl- et hètèroarylsilanes par scission de l'hexaméthyldisilane

Abstract In the presence of hexamethylphosphoramide and a catalytic quantity of tetrakis(triphenylphosphine)palladium, hexamethyldisilane reacts with various functional aryl bromides to give the corresponding aryisilanes in satisfactory yields. The reaction has been extended to fluorinated aromatics and, for the first time, to bromo-derivatives of pyridine and quinoline as well as to 3,4-dichlorotrifluoromethylbenzene. This process, which avoids the use of a stoichiometric amount of metal, is especially useful when the function attached to the aryl bromide is not compatible with common organometailic intermediates.

Original preparation of conjugates for antibody production against Amicoumacin-related anti-microbial agents

Amicoumacins are natural products with potent anti-ulcerogenic and anti-bacterial activities, and have been isolated from different Bacillus genera. They belong to a family of 3,4-dihydroisocoumarin derivatives bearing hydroxylated amino acid side chains. The 3,4-dihydroisocoumarin moiety of Amicoumacins has been obtained in two steps from 2-methoxybenzoic acid by combining directed and benzylic metalation strategies. The use of s-BuLi in both steps gave satisfactory and reproducible yields. For the development of an immunoassay (ELISA) of Amicoumacin-related compounds in biological media, the deprotected 3,4-dihydroisocoumarin moiety has been coupled to the BSA carrier protein via a homobifunctional linker deriving from d-tartaric acid. This approach enabled to introduce the hydroxylated portion of Amicoumacin directly during the preparation of hapten-protein conjugates. The coupling ratio was evaluated by mass spectrometry. The hapten-protein conjugate showing the best coupling ratio was used to generate polyclonal immunosera in rabbits. After immunoserum titration, ELISA conditions were set up and specificity tests were performed on solutions of pure parent compounds, semi-purified Amicoumacin B as well as on culture supernatants of strains known for their Amicoumacin production. This immunoassay is suitable for a rapid and simple screening test for the production of Amicoumacins and its related compounds by bacterial strains.

Une voie de synthese simple et rapide de phenols meta acyles

Abstract A new method for the meta acylation of anisole and its para-methyl or fluoro derivatives, is described. Addition of two trimethysilyl groups in the 2 and 5 positions (relative to the methoxy group), followed by hydrolysis affords the corresponding 5-trimethylsilyl-3-Cyclohexenones. Electrophilic substitution of the silyl group using RCOCl/2AlCl3 at low temperature provides, after final aromatisation promoted by Pd/C or CuBr2/LiBr, the expected meta acylated products. This mode of meta functionalization has been successfully applied to an original synthesis of ketoprofen starting from anisole.