Synthesis of 5-hydroxy-2-(β- d-ribofuranosyl)pyran-4-one from a pyranulose glycoside

Abstract

The synthesis of 5-hydroxy-2-(β- d-ribofuranosyl)pyran-4-one ( 9) is described. Treatment of pyranulose glycoside with bromine in carbon tetrachloride afforded brompyranulose glycoside in 90% yield. The reaction of (6 S)- and (6 R)-4-bromo-6-hydroxy-6-(2,3,5-tri- O-benzoyl-β- d-ribofuranosyl)-6 H-pyran-3-one ( 2) in acidic media was examined with the following results: the reaction of 2 with trifluoroacetic acid (TFA) in dioxane afforded a mixture of 5-hydroxy-2-(2,3,5-tri- O-benzoyl-β- d-ribofuranosyl)pyran-4-one ( 3) and its furan derivative 5-hydroxy-2-{5-(benzoyloxy)methyl]furan-2-yl}pyran-4-one ( 4), but the use of hydrochloric acid formed the bromofurfural, 3-bromo-5-(2,3,5-tri- O-benzoyl-β- d-ribofuranosyl)-2-furancarboxyaldehyde only. Acetylation of a mixture ( 3 and 4) with acetic anhydride facilitated product separation to give the corresponding acetates 5-acetoxy-2-(2,3,5-tri- O-benzoyl-β- d-ribofuranosyl)pyran-4-one ( 5) and 5-acetoxy-2-{5-[(benzoyloxy)methyl]furan-2-yl}pyran-4-one ( 6). Treatment of 5 with hydrazine afforded 3-hydroxymethyl-6-(β- d-ribofuranosyl)-1 H-pyridazin-4-one in 43% yield. Debenzoylation of 5 with aq ammonia gave 9 in 50% yield.