Abstract Novel radiolabeled O 6-benzylguanine derivatives, 2-amino-6-O-[11 C]- [(methoxymethyl) benzyloxy]-9-benzyl purines ([11 C] pO 6-AMBP, 1a;[11 C] mO 6-AMBP, 1b;[11 C] oO 6-AMBP, 1c), have been synthesized for evaluation as new potential positron emission tomography (PET) tumor imaging agents for the DNA repair protein, O 6- alkylguanine-DNA alkyltransferase (AGT). The appropriate precursors for radiolabeling ...