D. Anker

An efficient and highly stereoselective α(1→4) glycosylation between two d-galacturonic acid ester derivatives

Abstract The highly stereoselective α(1→4) coupling between two d -galacturonic acid ester derivatives was accomplished in good yields, for the first time, using a phenylthioglycoside as donor. The method was designed to prepare d -galacturonic acid oligomers with methyl ester groups in definite positions.

Synthese DE L′Amino-3-Fluoro-2-Tridesoxy-2,3,6-L-Galactose (α-Fluoro-2-L-Daunosamine)

Abstract 3-Amino-2-fluoro-2,3,6-trideoxy-L-galactose 10 (α-fluoro-L daunosamine) was synthesized in ten steps starting from methyl-2, 3-anhydro-4,6-0-benzylidene-α-D-mannopyranoside (overall yield 70%). Et3N, 3HF complex was used as the fluorinating agent, according to our previous work, for replacement of a mesyl groun. Neighbouring-group participation lead to a fluorinated product with retention of configuration. The structure of 10 was determined by 1H and 19F NMR spectroscopy.

Utilisation du palladium comme catalyseur de N,N-didesallylation

Resume Palladium on charcoal is more efficient than usual catalysts to perform N,N,-dideallylation of amines ; synthetic applications in aminosugars field using nitrogen atom transfer in a one pot reaction are described.

Synthèse et étude conformationnelle des quatre méthyl-2-amino-2,4-didésoxy-dl-pentopyranosides

Abstract The four methyl 2-amino-2,4-dideoxy- dl -pentopyranosides were synthesized starting from tetrahydro-2-methoxypyran-3-one. The introduction of a functional group at C-4 of the pyran ring was obtained by formation of the 3-dibenzylenamine derivative, hydroboration, oxidation, and catalytic di- N -debenzylation, giving methyl 2-acetamido-2,4-dideoxy-α- and -β- dl - threo -pentopyranosides. Isomerization at C-3 gave the corresponding erythro derivatives. The conformation of the four isomers as the O -acetylated derivatives was determined by n.m.r. spectrometry.

Cycloshydratation de dios in presence D'HMPT☆

Abstract 1,4 and 1,5-diols heated with 0.3 equivalent of HMPA undergo cyclodehydration leading to tetrahydrofurans and tetrahydropyrans.

Ouverture d'epoxydes par des acides organiques dans L'H.M.P.T.: nouvelle voie d'acces a des desoxypentopyranosides☆

Abstract The opening of pyranic epoxides with organic acids in HMPA leads to regioselectively esterified methyl deoxy threo pentopyranosides; one of them is a convenient intermediate to provide erythro isomers.

Synthese de L'Amino-2-desoxy-2-β-D-arabinopyranoside de Methyle

Abstract No convenient pathway is known to synthesize methyl-2-amino-2-deoxy-D-arabinopyranosides. Methyl-4-O-allyl-2,3-anhydro-β-D-ribopyranoside is easily obtained starting from D-arabinose but the opening of this epoxide with diallylamine is not regioselective, giving both xylo and arabino compounds. We found that participation of the diallylamino group, after mesylation of the mixture, leads to a lyxo aziridinium ion which is regioselectively opened. Trideallylation with palladium on charcoal gives methyl-2-amino-2-deoxy-β-D-arabinopyranosides in good yield.

Anchimeric assistance by the anomeric phenylthio group in the nucleophilic substitution of a 6-O-trifluoromethanesulfonyl-β-d-galactopyranoside

Abstract Nucleophilic displacement by the cyanide anion of the 6- O -triflyl group in phenyl 6- O -triflyl-2,3-di- O -benzyl-4- O - p -methoxybenzyl-1-thio-β- d -galactopyranoside takes place via an intermediate 1,6-sulfonium salt resulting from the anchimeric assistance of the C-1 phenylthio group.

Synthesis of methyl esters of 3-deoxy-d-erythro-2-hexulosonic acid (KDG) analogs, inducers of the expression of pectinase genes in bacteria Erwinia chrysanthemi

Abstract Two title compounds, methyl 3-deoxy- l -threo-2-hexulosonate 3 and methyl 3,5-dideoxy- d -glycero-2-hexulosonate 4, were prepared from d -glucono-1,5-lactone and proved to be gratuitous inducers of the expression of pectinase genes in the phytopathogenic bacteria Erwinia chrysanthemi.

Utilisation du borohydrure de sodium pour la reduction assistee de mesylates secondaires de diallylaminoglycosides ; nouvelle voie d'acces a la (=L)-daunosamine☆

Abstract Secondary mesylate in trans relationship with diallylamino group is reduced by means of a participation reaction affording deoxygenated aminoglycosides ; for one of them this reaction is a new pathway leading to (=L)-daunosamine.