Design, synthesis and inhibitory activity against Mycobacterium tuberculosis thymidine monophosphate kinase of acyclic nucleoside analogues with a distal imidazoquinolinone.

Thymidine monophosphate kinase from Mycobacterium tuberculosis (TMPKmt) has been proposed as an attractive target in the search of new agents to fight against tuberculosis. We recently reported that thymine derivatives carrying a naphtholactam or naphthosultam moiety at position 4 of a (Z)-butenyl chain inhibit TMPKmt in the subµM range. Here we describe the replacement of the planar naphtholactam and naphthosultam rings in our identified hits by 5,6-dihydro-1H-imidazo[4,5,1-ij]quinolinones and a 5,6-dihydro-1H,4H-1,2,5-thiadiazolo[4,3,2-ij]quinoline-2,2-dioxide where the planarity has been broken. Interestingly, these non-planar compounds were similarly potent against the target enzyme than their aromatic analogues, suggesting a bioisosteric behavior that may also be applied to other biologically active compounds. The synthesis of the different targeted imidazoquinolinones has been successfully performed via a hypervalent iodide mediated oxidative cyclization of N-methoxyureas catalized by bis(trifluoroacetoxy)iodobenzene (PIFA) expanding the reported use of this reagent for the synthesis of differently substituted imidazoquinolinones.