Magnesium plays an important role in infection with Mycobacterium tuberculosis ( Mtb) as a signal of the extracellular environment, as a cofactor for many enzymes, and as a structural element in important macromolecules. Raltegravir, an antiretroviral drug that inhibits HIV-1 integrase is known to derive its potency from selective sequestration of active-site magnesium ions in addition to binding to a hydrophobic pocket. In order to determine if essential Mtb-related phosphoryl transfers could be disrupted in a similar manner, a directed screen of known molecules with integrase inhibitor-like pharmacophores ( N-alkyl-5-hydroxypyrimidinone carboxamides) was performed. Initial hits afforded compounds with low-micromolar potency against Mtb, acceptable cytotoxicity and PK characteristics, and robust SAR. Elucidation of the target of these compounds revealed that they lacked magnesium dependence and instead disappointingly inhibited a known promiscuous target in Mtb, decaprenylphosphoryl-β-d-ribose 2'-oxidase (DprE1, Rv3790).