Sialic Acid 4-N-Piperazine and Piperidine Derivatives Bind with High Affinity to the P. mirabilis Sialic Acid Sodium Solute Symporter.

In search for novel antibacterial compounds, bacterial sialic acid uptake inhibition represents a promising strategy. Sialic acid plays a critical role for growth and colonisation of several pathogenic bacteria, and its uptake inhibition in bacteria was recently demonstrated to be a viable strategy by targeting the SiaT sodium solute symporters from Proteus mirabilis and Staphylococcus aureus. Here we report the design, synthesis and evaluation of potential sialic acid uptake inhibitors bearing 4-N-piperidine and piperazine moieties. The 4-N-derivatives were obtained via 4-N-functionalization with piperidine and piperazine nucleophiles in an efficient direct substitution of the 4-O-acetate of Neu5Ac. Evaluation for binding to bacterial transport proteins with nanoDSF and ITC revealed compounds possessing nanomolar affinity for the P. mirabilis SiaT symporter. Computational analyses indicate the engagement of a previously untargeted portion of the binding site.