Martine Lefeuvre

Chimie des sucres sans groupements protecteurs - I - esterification regioselective de l'hydroxyle anomere du lactose, du maltose et du glucose

Abstract Treatment of acyl chlorides 4 with mercaptothiazoline, mercapto- benzothiazole, p -nitrophenol and 8-hydroxyquinoline in the presence of Et 3 N, afforded high yields of the corresponding reactive amides 5a – h , S -thioesters 6e – h and aryl esters 7e – h and 8a – h , respectively. The esters 6e - h , 7e - h and 8e – h reacted with excess β-lactose in pyridine, to give the corresponding β-esters, 9e – h resulting from esterification of the anomeric hydroxyl of the sugar. The amides 5c , f – h gave the α-lactosyl esters 9c , f – h . The amide 5e and the esters 8b , c , e reacted with β-maltose, thus affording the corresponding β-maltosyl esters 10b , c , e , whereas the compounds 8a – e reacted with β-glucose, yielding the corresponding β-glucosyl esters 11a – e . This appears to be one of the very few selective chemical modifications of sugars known, which do not involve the toilsome protection-deprotection methology. The now commercially available maltosyl and glucosyl esters 10e and 11d – e are new non-ionic, and water-soluble detergents which could be used for studies of cell membrane proteins.

A new synthesis of carboxylic and carbonic acid anhydrides using phase transfer reactions

Abstract Acyl chlorides and alkylchloroformates smoothly reacted with one molar equivalent of sodium hydxoxide, using liquid-liquid phase transfer conditions to afford high yields of the corresponding symmtrical carboxylic and carbonic hemiester anhydrides. Unstable, anhydrides such as 4-nitrobenzoic, 2-furoic and methacrylic anhydrides, which are otherwise difficult to obtain, were easily prepared by this method. The reaction mechanism does not seem to involve intermediate hydrolysis of half the acid chloride into the corresponding sodium carboxylate.

Synthèse de dihydroxy phenacylidene triphenylphosphoranes nouveaux précurseurs de composés flavonoides: synthèse d'hydroxy-6 et hydroxy-7 chromones

Abstract The synthesis of two new dihydroxy phenacylidene triphenylphosphoranes from 2,4-dibenzoyloxy and 2,5-dibenzoyloxy acetophenones is described. By acylation of the hydroxyl groups of theses ylids, intramolecular of the esters carbonyl group and hydrolysis of the second esters group, some 6-hydroxy and 7-hydroxy chromones are prepared with good yields.

Sugar chemistry without protecting groups: A regioselective addition of the primary hydroxyl of monosaccharides to alkylisocyanates

The primary hydroxyl groups of D-glucose, D-galactose and methyl-α-D-glucoside add selectively to alkylisocyanates, thus affording respectively 6-O-carbamoyl-D-glycopy-ranoses and methyl-6-O-carbamoyl-α-D-glucopyranosides with high yields (except for galactosyl compounds), the temporary protection of the other hydroxyls of the starting sugars being not necessary in the present case.

Synthese de trihydroxyphenacylidenetriphenylphosphoranes une nouvelle voie d'acces aux dihydroxyflavones (chrysine, acacetine…)

Resume An easy and convenient synthesis of two new trihydroxyphenacylidentriphenylphosphoranes from phloroglucinal and pyrogallol is described. Some dihydroxyflavones are prepared by acylation of these ylids, intramolecular olefination and saponification of the two remaining ester groups.

β-Anomeric selectivity in the glycosidation of d-mannofuranurono-6,3-lactone catalyzed by boron trifluoride diethyl etherate

The BF3-promoted glycosylation of D-mannofuranurono-6,3-lactone with dodecanol or methanol afforded n-alkyl beta-D-mannofuranosidurono-6,3-lactone. Reduction of n-dodecyl beta-D-mannofuranosidurono-6,3-lactone with sodium borohydride yielded the corresponding alkyl beta-D-mannofuranoside.

Diastereospecific synthesis and amphiphilic properties of new alkyl β-D-fructopyranosides

In this article we describe a novel one step stereocontrolled synthesis of alkyl 1-O-β-D-fructopyranosides from totally unprotected D-fructose. In order to avoid oligomerization of D-fructose the reactions were performed in heterogeneous media. Thus, long chain alcohols, as acceptors, were treated with D-fructose in the presence of iron(III) chloride as the promoter to give the alkyl substituted products in yields of approximately 30%. The materials produced were found to self-organise and form liquid crystal mesophases. One of the thermotropic phases exhibited by this family of compounds was found to be atypical of liquid crystal modifications normally exhibited by glycolipids. The structure of this phase was investigated by a wide variety of techniques, and sufficient evidence was gained to indicate that it is novel. A variety of possible arrangements of the molecules in the self-organised state is given based on the preliminary data.