1. Antitumour imidazotetrazines. Part 36.1 Conversion of 5-aminoimidazole-4-carboxamide to imidazo[5,1-d?][1,2,3,5]tetrazin-4(3H?)-ones and imidazo[1,5-a][1,3,5]triazin-4(3H?)-ones related in structure to the antitumour agents temozolomide and mitozolomide Yongfeng Wang,Richard T. Wheelhouse,Linxiang Zhao,David A. F. Langnel,Malcolm F. G. Stevens J. Chem. Soc. Perkin Trans. 1 1998 1669