Interaction of 5-aminoimidazole-4-carboxamide with alkyl isocyanates y
ields N-substituted 1-carbamoylimidazoles which can be cyclised to imi
dazo[5,1-d][1,2,3,5]tetrazin-4(3H)-ones, including temozolomide 3a, on
nitrosation; a similar reaction with methyl isothiocyanate, followed
by nitrosation, affords the nitrosomethylamino derivative 11 of a new
ring-system, imidazo[1,5-b][1,2,4]thiadiazole.