2-Amino-8-[(4-bromophenyl)azo]-1,7-dihydro-6H-purin-6-one-13C2,15N is an intermediate in synthesizing 8-Aminoguanine-13C2,15N (A609862), which is an isotope labelled compound of 8-Aminoguanine (A609875) that accelerates DNA tetramolecular G-quadruplex formation.