Antitumour imidazotetrazines. Part 39. Synthesis of bis(imidazotetrazine)s with saturated spacer groups

Bis(imidazotetrazine)s (16), related in structure to the antitumour agents mitozolomide (1a) and temozolomide (1b), but linked through the N(3)–N(3′) atoms of the imidazo[5,1-d][1,2,3,5]tetrazine ring-systems, are prepared by interaction of 5-diazoimidazole-4-carboxamide (8) and diisocyanates (15). The presence of the polymethylene linker with/without sulfur and oxygen heteroatoms does not substantially affect the acid stability, base-catalysed decomposition, antitumour activity or DNA base alkylation preference characteristic of the unlinked imidazotetrazines mitozolomide and temozolomide.