A new route to the antitumour drug temozolomide, but not thiotemozolomide

Abstract

Interaction of 5-aminoimidazole-4-carboxamide with alkyl isocyanates yields N-substituted 1-carbamoylimidazoles which can be cyclised to imidazo[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.