Synthesis and characterization of azanonaborane-containing purine derivatives for boron neutron capture therapy

Derivatives of purine, adenine, guanine, and 2,6-diaminopurine linked to the azanonaborane (B₈N cluster) have been prepared, for possible use as powerful agents for boron neutron capture therapy (BNCT). The synthesis was carried out via a ligand exchange reaction. The exo-NH₂R group of the azanonaborane of the type [(RH₂N)B₈H₁₁NHR] can be exchanged by one hetero-nitrogen atom of the pyrimidine ring, and except for guanine, also by an N atom of the imidazole ring. The identity of the products was confirmed by NMR, elemental analysis, IR, and mass spectrometry. No reaction was found to occur with caffeine and theophylline under the same reaction conditions.