Synthesis and biological evaluation of new dipicolylamine zinc chelators as metallo-β-lactamase inhibitors

Antibiotics are key drugs in modern healthcare, especially in hospitals, where multiresistant bacteria resides and is a potential threat to human health. In the present work, a new series of adjuvants working synergistically with the carbapenem meropenem, in which a selective zinc-chelating agent was covalently linked to the small bacterial peptide D-Ala-D-Ala, was synthesized and tested against VIM-2 and NDM-1 metallo-β-lactamases (MBLs). The nature of the linker was modified in a structure-activity relationship study. Compound 1i, having an ethyl piperidine linker, lowered the MIC of meropenem from 32 to 64 mg/L to 2 and 1–2 mg/L against VIM-2- and NDM-1-producing clinical isolates, respectively. The IC50 value of 1i against VIM-2 was 9.8 and 2.2 μM after 5 and 20 min, respectively. Compound 1i also showed intrinsic toxicity against three eukaryotic human tumoral cell lines between 50 and 120 μM.