2-β-D-RIBOFURANOSYLBENZOXAZOLE FROM 2,5-ANHYDRO-D-ALLONOIMIDATE, AND 1,3-DIMETHYL-8-β-D-RIBOFURANOSYLXANTHINE FROM 2,5-ANHYDRO-D-ALLONO-THIOIMIDATES AND -DITHIOATES

Article abstract of DOI:10.1016/S0008-6215(00)90269-6

The ability of imidates, thioimidates, and dithioates to react with o-aminophenol (2) and 5,6-diamino-1,3-dimethyluracil (6) was studied, using nonsaccharide model compounds, as well as saccharide derivatives.All of the model compounds gave 2-methylbenzoxazole, but only ethyl dithioacetate gave a purine derivative with 6.Methyl 2,5-anhydro-D-allonoimidate hydrochloride reacted with 2 to yield 2-β-D-ribofuranosylbenzoxazole, but failed to react with compound 6.On reaction with compound 6 such fully acylated thioimidates as ethyl and benzyl 2,5-anhydrotri-O-benzoyl- or tri-O-p-toluoyl-D-allonothioimidate hydrochloride yielded amidines that underwent aromatization of the furanose ring.Such monoacylated thioimidates as ethyl or benzyl 2,5-anhydro-6-O-benzoyl-D-allonothioimidate hydrochloride yielded, with compound 6, 8-(5-O-benzoyl-β-D-ribofuranosyl)-1,3-dimethylxanthine, without aromatization.Such dithioates as benzyl 2,5-anhydro-6-O-benzoyl-D-allonodithioate and ethyl 2,5-anhydrotri-O-benzoyl-D-allonodithioate were obtained by treating the corresponding thioimidate with H2S in pyridine.With compound 6, the first yielded 8-(5-O-benzoyl-β-D-ribofuranosyl)-1,3-dimethylxanthine, which afforded the free C-nucleoside 1,3-dimethyl-8-β-D-ribofuranosylxanthine on treatment with methanolic ammonia.