Antitumour imidazotetrazines. Part 31. The synthesis of isotopically labelled temozolomide and a multinuclear (1H, 13C, 15N) magnetic resonance investigation of temozolomide and mitozolomide

The antitumour drug temozolomide has been synthesized isotopically labelled with NMR active nuclei at a variety of sites and all its 13C and 15N NMR spectral resonances have been assigned. At low pH a site of protonation has been identified which accounts for the acid stability of the drug