Carbohydrate-Templated Syntheses of Trifluoromethyl-Substituted MEP Analogues for the Study of the Methylerythritol Phosphate Pathway.

Trifluoromethyl analogues of methylerythritol phosphate (MEP) and 2-C-methyl-erythritol 2,4-cyclodiphosphate (MEcPP), natural substrates of key enzymes from the MEP pathway, were prepared starting from d-glucose as the chiral template to secure absolute configurations. The obligate trifluoromethyl group was inserted with complete diastereoselectivity using the Ruppert-Prakash nucleophile. Target compounds were assayed against the corresponding enzymes showing that trifluoro-MEP did not disrupt IspD activity, whereas trifluoro-MEcPP induced 40% inhibition of IspG at 1 mM.

Irreversible Inhibition of IspG, a Target for the Development of New Antimicrobials, by a 2-Vinyl Analogue of its MEcPP Substrate.

IspG (also called GcpE) is an oxygen-sensitive [4Fe-4S] enzyme catalyzing the penultimate step of the methylerythritol phosphate (MEP) pathway, a validated target for drug development. It converts 2-C-methyl-d-erythritol-2,4-cyclo-diphosphate (MEcPP) into (E)-4-hydroxy-3-methyl-but-2-enyl-1-diphosphate (HMBPP). The reaction, assimilated to a reductive dehydration, involves redox partners responsible for the formal transfer of two electrons to substrate MEcPP. The 2-vinyl analogue of MEcPP was designed to generate conjugated species during enzyme catalysis, with the aim of providing new reactive centers to be covalently trapped by neighboring amino acid residues. The synthesized substrate analogue displayed irreversible inhibition towards IspG. Furthermore, we have shown that electron transfer occurs prior to inhibition; this might designate conjugated intermediates as probable affinity tags through covalent interaction at the catalytic site. This is the first report of an irreversible inhibitor of the IspG metalloenzyme.