Summary
Reaction of 6-hydrazino-l,3-dimethyluracil (1) with glycosyl isothiocyanates (2a,b,c) gave the glycosyl thiosemicarbazides (3a,b,c) in good yield, which were cyclized to pyrimidothiadiazines (5a,b,c) with NBS oxidation. And 5a,b,c were converted to pyrazolopyrimidines (6a,b,c) by thermal desulfurization. Reaction of aldoses (7a-d), ketoses (11a,b), and D-glucuronolactone (14) with 1 gave hydrazones (8a-d,12a,b,l5) in good yield, which were converted to pyrimidopyridazines (9a-d, l0a-d, 13a,b, 16) by cyclodehydration reaction.