Abstract
Pyridopyrimidine reacted with aromatic aldehydes afforded the arylhydrazone 2a,b which could be cyclized into the pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine 3a,b, with formic acid, and carbon disulphide to give pyrido[2,3-d][1,2,4]traizolo[4,3-a]pyrimidine 4, 5. Reaction of I with nitrous acid afforded tetrazolo[1,5-a]pyrido[2,3-d]pyrimidine 6, which was reduced by zinc dust to give 2-amino-pyrido[2,3-d]pyrimidine 7. Finally the reaction of 2-hydrazino 1 with D-xylose or D-glucose afforded the acyclic N-nucleoside 8, 11 which were converted into tetra/penta O-acetate acyclic C-nucleoside 9, 12 in acetic anhydride/pyridine. De-acetylation of compounds 9, 12 afforded C-nucleosides 10, 13.