Synthesis and Biological Activity of Tetrahydropyrido[2′,3′:4,5]imidazo[1,2‐c]pyrimidine‐6,8‐diones

Substituted 4‐oxoquinoline‐3‐ ( 1a ) and 4‐oxo‐1,8‐naphthyridine‐3‐ ( 1b ) carboxylic acids are clinically useful antibacterial agents exerting their activity by inhibiting the subunit A of DNA gyrase. Recently, pyrimido‐[1,6‐ a ]benzimidazoles 2 were found to be a new class of inhibitors of this enzyme. As, in 1 , replacement of C(8) by the N‐atom was shown beneficial for the biological properties, a synthesis of the corresponding aza analogues of 2 has been carried out. The synthesis, DNA gyrase inhibitory activity, and in vitro antibacterial activity of the target compounds 16–19 are reported.