Catherine Lievre

Synthesis of 1,1-dibromo-1-alkenes from partially and unprotected aldoses

Abstract Partially and unprotected aldoses react with dibromomethylenetriphenylphosphorane, generated in situ from dibromomethyltriphenylphosphonium bromide in the presence of zinc, to give corresponding unsaturated Wittig adducts in good yields.

Synthesis of glyco-1-ynitols via 1,1-dibromo-1-alkenes from partially and unprotected aldoses

Abstract We report the synthesis of 1,1-dibromo-1-alkenes from partially and unprotected aldoses and the synthesis of glyco-1-ynitols from these dibromocompounds. The 1,1-dibromo-1-alkenes were obtained by the reaction of dibromomethyl-triphenylphosphonium bromide in the presence of zinc in refluxing 1,4-dioxane. As an example, when the reaction is performed on 2-deoxy-5-O-trityl- d -ribofuranose ( 1 ) the corresponding 1,1-dibromo-1-olefin, (2R,3S)-6,6-dibromo-1-O-trityl-hex-5-ene-1,2,3-triol ( 12 ), is obtained in 89% yield. These smooth reaction conditions led also to the achievement of the other olefins from other sugars with good yields (44–90%). The reaction of these olefins with n-butyllithium in THF at low temperature afforded the corresponding alkynes. So the reaction of (2R,3S)-6,6-dibromo-1-O-trityl-hex-5-ene-1,2,3-triol ( 12 ) with this alkyllithium reagent led to (2R,3S)-1-O-trityl-hex-5-yne-1,2,3-triol ( 23 ) in 87% yield. Other glyco-1-ynitols were obtained with satisfying yields (64–87%).

Réaction de type Wittig sur des aldoses non protégés: Synthèse d'esters α,β-insaturés

Abstract Unprotected aldoses react with methylbromoacetate in presence of n-tributylphosphine and zinc to give stereoselectively with good yields the corresponding E unsaturated Wittig adducts.

Réactions de type Wittig sur des aldoses partiellement protégés: Synthèses d'aldooctènoates et octènonitriles de stéréochimie E acycliques

Abstract Mono or di-protected aldoses react with methyl bromoacetate or bromoacetonitrile, in presence of tri-n-butylphosphine and zinc, to give stereoselectively with good yields the corresponding E unsaturated Wittig adducts.

Synthèses de C-glycosides : utilisations d'un dérivé de l'arsenic

Abstract Reaction of arsenic ylides with pyranose and furanose carbohydrates mainly leads to E-olefinic derivatives. Cyclisation of the olefinic derivatives obtained from 2,3,4,6-tetra-O-benzyl-D-glucose and D-galactose, promoted by ZnBr2, gives C-glycosyl compounds with high stereoselectivity. One the other hand, reaction of the corresponding arsonium salt, in presence of zinc, with a furanose derivative gives directly and stereoselectively the β-C-glycosyl compound.

Réaction d'aldoses partiellement protégés avec des ylures d'arsenic stabilisés: synthèse de dérivés insaturés E acycliques et de dérivés C-glycosyle

Abstract The reaction of partially protected aldoses with (carbomethoxymethyl)triphenylarsonium bromide and zinc in toluene gave E α,β-unsaturated acyclic esters. When intramolecular transest erification occurred, bicyclic 1,4-lactone derivatives were formed concurrently. Otherwise, using these non alcaline conditions, olefination did not favour the formation of C -glycosyl derivatives. On the other hand, when the reaction was performed with (carbomethoxymethylene)triphenylarsorane in toluene, followed by the addition of n -butyllithium, bicyclic derivatives were obtained rapidly in good yields. Moreover, when cyanomethyltriphenylarsonium bromide was used in place of (carbomethoxymethyl)triphenylarsonium bromide, the corresponding E aldooctenonitriles were produced in satisfactory yields.

SYNTHESE DE 1,2-CIS C-GLYCOFURANOSIDES DERIVES D'ALDOSES NON PROTEGES

Abstract Reaction of D-glucose, D-galactose or D-xylose with carbomethoxymethylenetriphenylarsonium ylide in refluxing dioxane leads to corresponding 3,6-anhydro-2-deoxy-octono or heptono-1,4-lactones in good yield.