Toward unsymmetrical 2,6-bistriazolylpurine nucleosides

Synthetic routes toward purine derivatives containing two different 1,2,3-triazolyl substituents at their C-2 and C-6 positions were developed. 2,6-Bistriazolylpurines containing electron-withdrawing substituents in their triazole rings undergo C-6-selective SNAr reactions with other triazoles or NaN3. In the latter case, a CuAAC reaction provides differently substituted 2,6-bistriazolylpurines. Also a general synthetic sequence toward the title compounds regardless of their electronic character was developed. It makes a use of 6-amino-2-azidopurine derivatives, which are obtained by C-6-selective reduction of 2,6-diazidopurines.