SYNTHESIS OF ACYCLO C-NUCLEOSIDES - L)-5-METHYL-7-OXO-1,2,4-TRIAZOLO[4,3-A]PYRIMIDINES

Condensation of 2-hydrazino-6-methyl-4-oxo-pyrimidine (1) with aldopen toses 2a-d or aldohexoses 2e-g gave the corresponding aldehydo-sugar ( 6-methyl-4-oxo-2-pyrimidinyl)hydrazones 3a-g which were acetylated to the corresponding per-O-acetyl-aldehydo-sugar (3-acetyl-6-methyl-4-oxo -2-pyrimidinyl)hydrazones 4a-g. Cyclization of the latter compounds wi th Br-2-HOAc-NaOAc gave the corresponding acyclo C-nucleoside peraceta tes 6a-g. Oxidative cyclization of 3a-g with Br-2-H2O gave the corresp onding acyclo C-nucleosides 9a-g which were acetylated to the correspo nding acyclo C-nucleoside peracetates 6a-g. The latter were also obtai ned by one-pot cyclization/ acetylation of hydrazones 3a-g by treatmen t with Br-2-HOAc-NaOAc followed by Ac2O. De-O-acetylation of the acycl o C-nucleoside peracetates 6a-g with methanolic ammonia gave the l)-5- methyl-7-oxo-1,2,4-triazolo[4,3-a]pyrimidines 10a-g.