Synthesis and Bioactivity of β-Substituted Fosmidomycin Analogues Targeting 1-Deoxy-d-xylulose-5-phosphate Reductoisomerase

Abstract

ABSTRACT. In the wake of the escalating development of resistance to currently available drugs, blocking the vital MEP pathway for isoprenoid biosynthesis in pathogens such as Plasmodia or Mycobacteria offers interesting prospects for inhibiting their growth. Although the natural product retro-hydroxamate fosmidomycin and its homologue FR900098 potently inhibit 1-deoxy-D-xylulose-5-phosphate reductoisomerase (Dxr), a key enzyme in the MEP pathway, their in vivo activity is compromised due to poor absorption and a suboptimal pharmacokinetic profile. In an effort to facilitate cellular uptake, we introduced aryl or aralkyl substituents at the β-position of the hydroxamate analogue of FR900098. While direct addition of a β-aryl moiety resulted in poor inhibition, longer linkers between the carbon backbone and the phenyl ring were generally associated with better binding to the enzymes, as well as activity against P. falciparum.X-ray structures of the parasite Dxr-inhibitor complexes show that the modes of binding of the two classes of compounds are in fact different. When the "shorter" compounds were bound, the active site flap was fully ordered and similar to that observed for the retro-hydroxamates. The "longer" compounds generate a substantially different flap structure, in which a key tryptophan residue is displaced, and the aromatic group of the ligand lies between the tryptophan and the methyl group on the hydroxamate. Although the most promising new Dxr inhibitors lack activity against E. coli and M. smegmatis, they proved to be highly potent inhibitors of Plasmodium falciparum in vitro growth.3

Targeting an Aromatic Hotspot in Plasmodium falciparum 1‐Deoxy‐d‐xylulose‐5‐phosphate Reductoisomerase with β‐Arylpropyl Analogues of Fosmidomycin

“…[d] Values of 0.051 and 0.018 were reported earlier for EcDxr and PfDxr, respectively . [e] A value of 0.117±0.012 was reported earlier . [f] A value of 0.43±0.09 was reported earlier .…”

“…[e] A value of 0.117±0.012 was reported earlier . [f] A value of 0.43±0.09 was reported earlier . [g] Not determined; 86 % activity remained after the addition of 100 μ m 6 j .…”

“…The final compounds were tested for inhibition of recombinant EcDxr and PfDxr using a spectrophotometric assay monitoring the substrate‐dependent oxidation of NADPH associated with the Dxr‐catalyzed reaction (Table ) . None of the changes introduced in 6 a – 6 j improve inhibition of EcDxr relative to 5 d , although 6 a , 6 c , 6 d and 6 f are essentially equipotent to 5 d .…”

“…Recently, we assessed the ability of Dxr to accommodate substituents in the β‐position of fosmidomycin analogues bearing a hydroxamate rather than the original reverse hydroxamate group . We observed that direct introduction of aromatic rings at the β‐carbon (as in 5 a ) afforded moderate Dxr inhibitors.…”

Identification of natural compound inhibitors against PfDXR: A hybrid structure‐based molecular modeling approach and molecular dynamics simulation studies

“…This raises the concern for the search of novel inhibitors that can inhibit the functioning of Pf DXR. As a result, a number of fosmidomycine derivatives along with other inhibitors have been synthesized and crystallized . Extensive crystallographic studies have unlocked the possibilities for the use of computational approaches to discover novel antimalarials against this target .…”