-Edited Guanine Isosteres.

Guanine is one out of five endogenous nucleobases and of key interest in drug discovery and chemical biology. Hitherto, the synthesis of guanine derivatives involves lengthy multistep sequential synthesis of low overall diversity, resulting in the quest for innovation. Using a "single-atom skeletal editing" approach, we designed 2-aminoimidazo[2,1-][1,2,4]triazin-4(3)-one as a guanine isostere, conserving the biologically important HBA-HBD-HBD (HBA = hydrogen bond acceptor; HBD = hydrogen bond donor) substructure.