In Pursuit of Natural Product Leads: Synthesis and Biological Evaluation of 2-[3-hydroxy-2-[(3-hydroxypyridine-2-carbonyl)amino]phenyl]benzoxazole-4-carboxylic acid (A-33853) and Its Analogues: Discovery of N-(2-Benzoxazol-2-ylphenyl)benzamides as Novel Antileishmanial Chemotypes

The first synthesis and biological evaluation of antibiotic 31 (A-33853) and its analogues are reported. Initial screening for inhibition of L. donovani, T. b. rhodesiense, T cruzi, and P. falciparum cultures followed by determination of IC50 in L. donovani and cytotoxicity on L6 cells revealed 31 to be 3-fold more active than miltefosine, a known antileishmanial drug, Compounds 14, 15, and 25 selectively inhibited L. donovani at nanomolar concentrations and showed much lower cytotoxicity.