(S)‑N‑Methyldihydroquinazolinones are the Active Enantiomers of Retro‑2 Derived Compounds against Toxins

This study reports the synthesis, chromatographic separation, and pharmacological evaluation of the two enantiomers of a new compound, named Retro-2.1, active against toxins by inhibiting intracellular trafficking via the retrograde route. The absolute configuration of the bioactive enantiomer has been assigned from X-ray diffraction to the (S)-enantiomer. To date, (S)-Retro-2.1 is the most potent molecule to counteract the cytotoxic potential of ricin and Shiga toxin, with EC50 values of 23 and 54 nM, respectively.