Virtual screening and crystallographic studies reveal an unexpected γ-lactone derivative active against MptpB as a potential antitubercular agent.

Mycobacterial resistance is a rapidly increasing phenomenon requiring the identification of new drugs effective against multidrug-resistant pathogens. The inhibition of protein tyrosine phosphatase B (MptpB), which interferes with host immune responses, may provide a new strategy to fight tuberculosis (TB), while preventing cross-resistance issues. On this basis, starting from a virtual screening (VS) campaign and subsequent structure elucidation studies guided by X-ray analyses, an unexpected γ-lactone derivative (compound 1) with a significant enzymatic activity against MptpB was identified. The structural characterization of compound 1 was described by means of NMR spectroscopy, HRMS, single crystal X-ray diffraction and Hirshfeld surface analysis, allowing a detailed conformational investigation. Notably, the HPLC separation of (±)-1 led to the isolation of the most active isomer, which emerged as a very promising MptpB inhibitor, with an IC value of 31.1 μM. Overall, the new chemotype described herein might serve as a basis for the development of novel treatments against TB infections.