Micheline Grignon-Dubois

Composition of sugarcane waxes in rum factory wastes

Wastes produced during fermentation and distillation of crude sugarcane juice in rum factories were evaluated as a new source of waxes. The chemical composition of the crude wax extracted from adsorbat of the wastes on fullers earth was studied by GC-mass spectrometry. Series of linear alkanes (C19-C33), and wax esters constitute the main components. In addition, phytosterols, triterpene methyl ethers, ethyl and methyl esters of fatty acids, and free fatty acids were found as minor components. Acid (predominance of C16 and C18) and alcohol portions (C26-C32) of the wax esters were analysed after saponification.

Sulfonation comparee de groupes divers lies au silicium. Application a la synthese d'acides sulfoniques nouveaux

Abstract Sulphonation by trimethylsilyl chlorosulphonate of various substituted silicon compounds is regiospecific or highly regioselective at the silicon atom, the reaction order is found to be: allyl > α-naphthyl > phenyl > vinyl. Sulphonation of various mono- and di-silylated derivatives leads to trimethylsilylmono- and in some cases to trimethylsilyldisulphonates which by hydrolysis form new sulphonic acids. The orientation of the sulphonation is determined by the position of the silicon atom. The nature of cyclohexyl hinders sulphonation (cyclo-C 6 H 11 Si is much less reactive than MeSi), while cyclopropanyl, due to its π-character, is much more reactive.

Synthese stereospecifique de butenyl-2 cetones et de l'acide butene-2 sulfonique

Abstract 1-Trimethylsilyl 2-methylcyclopropane cis or trans resulting from the silylation of 1-bromo 1-propene is a convenient regio- and stereospecific precursor of β,γ-unsaturated Z or E ketones and 2-butene sulfonic acid.

First Phytochemical Evidence of Chemotypes for the Seagrass Zostera noltii

The variability of the flavonoid content of two populations of Z. noltii from different geographical zones, i.e., the Bay of Arcachon and the Bay of Cadiz, was evaluated. Samples were collected in spring and autumn at the two sites, and extracts were prepared by maceration in water. The phenolic content was fully characterized using Nuclear Magnetic Resonance (NMR), UV and Liquid Chromatography-Mass Spectrometry (LC-MS), and the concentration of the individual phenolic was determined by quantitative High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD). The two populations show a strong geographical differentiation in their flavonoid content. The samples from Cadiz were dominated by apigenin 7-sulfate, which represents 71% (autumn collection) and 83% (spring collection) of the total flavonoids, whereas the samples from Arcachon were characterized by diosmetin 7-sulfate (85 and 93% of the total flavonoids). Structural elucidation of the individual phenolics was assigned using the complementary information from their spectral evidence. In addition, the results were confirmed by acid hydrolysis of the flavonoid sulfates, and comparison to synthetic standards obtained by sulfation of apigenin, diosmetin and luteolin. The results represent the first experimental evidence of the existence of chemotypes within the species Z. noltii.

Nouvelles fonctionnalisations a partir de cyclopropanes silicies

Abstract cis - and trans -1,2-Bis(trimethylsilyl)cyclopropane react with trimethylsilyl chlorosulfonate or acetyl chloride/aluminium chloride to afford the trans -sulfonyl or -acetyl derivatives resulting from substitution of one trimethylsilyl group without ring opening. The results confirm the effect of the trimethylsilyl group previously observed for trimethylsilylcyclopropane. In contrast cis - and trans -1-trimethylsilyl 2-(trimethylsilylmethyl)cyclopropane undergo facile diacylation with ring opening. This reaction offers a new, competitive acces to bifunctional butenes and especially to diacyl derivatives.

Acetylation de dimethyl-1,1 silacyclopentenes-3. Synthese de cetones ethyleniques β-siliciees

Abstract Acetylation of substituted or unsubstituted 1,1-dimethylsilacyclopent-3-enes by means of CH 3 COClAlCl 3 and (CH 3 CO) 2 OBF 3 occurs with ring opening and leads to two types of β-silylated ethylenic ketones: siloxanic ketones in the case of CH 3 COClAlCl 3 , and β-fluorosilylketones with (CH 3 CO) 2 OBF 3 . According to the substitution degree of the double bond of the starting silacyclopentenes, acetylation gives conjugated or unconjugated ketones, the latter resulting from the isomerization of the former ones. An interpretation of these results is proposed.

Bicyclo[n.1.0]alkylsilanes: Nouvelle synthese et reactivite

Abstract A new and competitive synthesis of bicyclo[n.1.0]trimethylsilanes is reported, involving a facile and rapid process, and giving both endo and exo isomers. The behavior of these species towards acids (HCl, (AcOH)2BF3) has been investigated. The stereochemistry of the substrate does not influence the regiochemistry of the electrophilic attack, while the stereochemistry of the largest ring plays a decisive role. Ring-opening of the cyclopropane ring was observed if it was bonded to a five- or six-membered ring while CSiMe3 cleavage occurred if it was bonded to the eight-membered ring. The results bring to light new perspectives for functionalization of cycloolefins via cyclopropanation.

An electron spin resonance study of the ring-opening of silyl-substituted cyclopropylmethyl radicals

Abstract ESR spectroscopy has been used to monitor the radicals formed when the silylated cyclopropanes (A–H) react with t-butoxyl radicals from photolysis of di-t-butyl peroxide.

Synthese de nouveaux acides sulfoniques et de sila-sultones ethyleniques

Abstract The sulfonation of 1-sila-3-clopentenes and corresponding silabicyclohexanes by CISO 3 SiMe 3 leads to novel ethylenic silasultones which are hydrolyzed to their sulfonic acids. Depending upon the degree of substitution of the double bond or cyclopropane ring, a competition may occur between the usually observed C-Si bond cleavage and the until now more rarely observed CH cleavage. An interpretation of these results is proposed.

The economic potential of beach-cast seagrass – Cymodocea nodosa: a promising renewable source of chicoric acid

Abstract Detrital and fresh specimens of the seagrass Cymodocea nodosa (Cymodoceaceae) from the Atlantic Ocean and Mediterranean Sea were screened for their phenolic content. For the first time, the major polyphenol was identified as chicoric acid (CA) by means of nuclear magnetic resonance, ultraviolet spectra, liquid chromatography/mass spectrometry, and comparison with standards. The CA content of the crude extracts was determined by quantitative high-performance liquid chromatography. The values found in the leaves ranged from 8.13 to 27.44 mg g-1 dw. The concentration was smaller in the rhizomes, with 0.31–3.70 mg g-1 dw. The phenolic profile was found to be similar whatever the geographical location in the Atlantic Ocean or the Mediterranean Sea. Considering the demonstrated therapeutic applications of CA, its high value on the nutraceutical market, and its rare occurrence in the plant kingdom, the high content found in C. nodosa detrital leaves makes this abundant biomass of interest for dietary and pharmaceutical applications.