Dérivés du C-méthyl-3-xylofurannose

3-C-Methylxylofuranose Derivatives 3′-C-methyladenosine has been known for almost ten years whereas its 3′-epimer is still to be prepared, because of the difficulty of synthesizing the 3-C-methylxylo-furanose. In this communication, the synthesis of 1,2-O-isoproypylidene acetal 9 and its derivatives is described. Vicinal dihydroxylation of 5-O-benzoyl-3-deoxy-1,2-O-isopryopylidene-3-C-methylidene-α-D -erythro-pentofuranose ( 6 ) led to the branchedchain sugar derivative 7 which was selectively tosylated to 8 whose reduction gave 9 . These reactions, as well as the derivatizations of 7 , 8 and 9 , took place with good to excellent yields.     

Structure du méthyl-3 phénylamino-4 phényl-5 triazole-1,2,4

The crystal structure or 3-methyl-4-phenylamino-5-phenyl-1,2,4-triazole has been determined by X-ray diffraction. It allows one to choose between the two reaction mechanisms which can be taken into account for the reaction of hydrazine upon N-acylated hydrezonates.     

Sur l'acylation des méthylfluorènes VI. Formylation du méthyl-2-fluorène et du méthyl-3-fluorène selon Rieche

The formylation of 2-methylfluorene and of 3-methylfluorene according Rieche yields 2-methyl-7-fluorene-carbaldehyde and 3-methyl-2-fluorenecarbaldehyde respectively. The constitution of the obtained aldehydes is proved by their conversion into the known 2,7-dimethyl-fluorene and 2,7-dimethyl-9-fluorenone, respectively into the known 2,3-dimethylfluorene and 2,3-dimethyl-9-fluorenone.     

Synthèse énantiospécifique du (—)-(1S,3R,5R)-1,8-diméthyl-3-éthyl-2,9-dioxabicyclo[3.3.1]non-7-ène

Enantiospecific Synthesis of (—)-(1S,3R,5R)-1,8-Dimethyl-3-ethyl-2,9-dioxabicyclo[3.3.1]non-7-ene The isomer (—)-(1S,3R,5R)-1,8-dimethyl-3-ethyl-2,9-dioxabicyclo[3.3.1]non-7-ene ((1S,3R,5R)- 8 ) was synthesized from (—)-(3R)-methyl 3-hydroxypentanoate with an enantiomeric excess ≥ 96%.     

Synthèse et désamination enzymatique des C-hydroxyméthyl-3′- et C-méthyl-3′-β-D-xylofurannosyl-9-adénines

Synthesis and enzymatic deamination of 3′-C-hydroxymethyl- and 3′-C-methyl-β-D -xylofuranosyl-9-adenines The title compounds have been prepared by classical synthetic steps after having optimized the nature of the blocking groups. Both nucleosides were found to be substrates of adenosine aminohydrolase which proved that C(3′)-branched-chain sugar nucleosides can be deaminated when the branched-chain is exo (trans relative to the base) if a suitably disposed hydroxy group is available on the endo side of the furanose ring.