Synthesis and evaluation of tetrahedral intermediate mimic inhibitors of 3-deoxy-d-manno-octulosonate 8-phosphate synthase

3-Deoxy-d-manno-octulosonate 8-phosphate (KDO8P) synthase catalyses the first committed step in the biosynthesis of 3-deoxy-d-manno-octulosonate (KDO), an important component of the lipopolysaccharide of Gram-negative bacteria. The pathway for KDO biosynthesis has been identified as a potential target of antibacterial drug design. The reaction catalysed by KDO8P synthase is an aldol-like condensation between phosphoenolpyruvate (PEP) and d-arabinose 5-phosphate (A5P) and proceeds through a bisphosphorylated tetrahedral intermediate. In this study a bisphosphate analogue of the tetrahedral intermediate was synthesised and was found to inhibit the metal-dependent KDO8P synthase from Neisseriameningitidis and the metal-dependent KDO8P synthase from Acidithiobacillus ferrooxidans with inhibition constants in the low micromolar range. Additionally, monophosphorylated inhibitors were synthesised to determine the relative importance of the two phosphate groups of this bisphosphate analogue for enzyme inhibition. The removal of either of these two phosphate groups gave less potent inhibitors for both enzymes.