The tetrahydro-β-carboline scaffold has proven fertile ground for the discovery of antimalarial agents (e.g., MMV008138 (1) and cipargamin (2)). Similarity searching of a publicly disclosed collection of antimalarial hits for molecules resembling 1 drew our attention to N2-acyl tetrahydro-β-carboline GNF-Pf-5009 ((±)-3b). Compound purchase, “analog by catalog”, and independent synthesis of hits indicated the benzofuran-2-yl amide portion was required for in vitro efficacy against P. falciparum. Preparation of pure enantiomers demonstrated the pharmacological superiority of (R)-3b. Synthesis and evaluation of D- and F-ring substitution variants and benzofuran isosteres indicated a clear structure-activity relationship. Ultimately (R)-3b was tested in Plasmodium berghei-infected mice; unfavorable physicochemical properties may be responsible for the lack of oral efficacy.
Hanan Almolhim, Sha Ding, Joshua H Butler, Emily K Bremers, Grant J Butschek, Carla Slebodnick, Emilio F Merino, Zaira Rizopoulos, Maxim Totrov, Maria B Cassera, Paul R Carlier. ACS Med. Chem. Lett. 2022, 13, 3, 371–376. https://doi.org/10.1021/acsmedchemlett.1c00697