Synthesis and antimicrobial activity of acyclo C-nucleosides : 3-(alditol-1-yl)-7-oxo-5-phenyl-1,2,4-triazolo[4,3-a]pyrimidines

Condensation of 2-hydrazino-4-oxo-6-phenylpyrimidine (1) with aldopentoses 2a-d or aldohexoses 2e-g gave the corresponding aldehydo-sugar (4-oxo-6-phenylpyrimidin-2-yl)hydrazones 3a-g which were acetylated to the corresponding poly-O-acetyl-aldehydo-sugar (3-acetyl-4-oxo-6-phenylpyrimidin-2-yl)hydrazones 4a-g. The latter compounds underwent oxidative cyclization with bromine in acetic acid and in the presence of sodium acetate to the corresponding 8-acetyl-3- (poly-O-acetyl-alditol-1-yl)-7-oxo-5-phenyl-1,2,4-triazolo[4,3-a]pyrimid ines 6a-g. Compounds 6a-g were also obtained by consecutive one-pot oxidative cyclization/acetylation in which the parent hydrazones 3a-g were treated with bromine/acetic acid/sodium acetate followed by acetic anhydride. Deacetylation of 6a-g with ammonium hydroxide in methanol gave the title compounds 7a-g. The antibacterial and antifungal activities of compounds 3c, 3f, 7c and 7f are reported.