Design, development and synthesis of ribitylaminopyrimidinedione derivatives as lumazine synthase mechanistic probes and trifluoromethylated pyrazoles as riboflavin synthase inhibitors

Yujie Zhao, Purdue University

Abstract

Inhibition of riboflavin synthase and lumazine synthase, the last two enzymes in the riboflavin biosynthetic pathway, provides a strategy for the development of therapeutically useful antibiotics. A homologous series of four derivatives of 5-amino-6-ribitylamino-1 H-pyrimidine-2,4-dione were designed and synthesiszed as potential enzyme inhibitors and mechanistic probes. Some of them displayed moderate inhibition activity on Mycobacterium tuberculosis lumazine synthase and riboflavin synthase. More tests need to be done. Molecular modeling was performed for one of the analogues bound to M. tuberculosis lumazine synthase. The hypothetic model suggests that both the hypothetical intermediate in the lumazine synthase-catalyzed reaction pathway and the metabolically stable analogs bind similarly. A high-throughput screening (HTS) hit compound displayed moderate inhibition of M. tuberculosis and Escherichia coli riboflavin synthases. The hit compound, whose structure was reassigned as [3-(4-chlorophenyl)-5-hydroxy-5-(trifluoromethyl)-4,5-dihydro-1H-pyrazol-1-yl]( o-tolyl)methanone (53), had a K is of 8.7 μM vs. M. tuberculosis riboflavin synthase and had moderate antibiotic activity against both M. tuberculosis replicating phenotype and non-replicating persistent phenotype. Molecular modeling studies suggest that two inhibitor molecules bind in the active site of the enzyme, that the binding is stabilized by stacking between the benzene rings of two adjacent ligands. The HTS hit compound and its analogs provide the first examples of riboflavin synthase inhibitors with antibiotic activity.

Degree

M.S.

Advisors

Cushman, Purdue University.

Subject Area

Organic chemistry

COinS