Enhancing lectin recognition via precise fluorination: Man5 glycomimetics for targeting DC-SIGN

High-mannose N -glycans, particularly Man 9 GlcNAc 2 , are key DC-SIGN ligands but remain synthetically challenging, motivating the development of accessible glycomimetics capable of reproducing lectin recognition. Here, we report a precise fluorination strategy to enhance DC-SIGN recognition using Man 5 -based glycomimetics. Four fluorinated Man 5 derivatives were synthesized with selective substitution at C-2 and/or C-6 of terminal mannoses, preserving Ca 2+ coordination. Biophysical evaluation revealed a strong positional dependence: C-6 fluorination markedly increased affinity, whereas C-2 substitution reduced binding. The (6F,6F)-Man 5 derivative 1 exhibited the highest inhibitory potency, surpassing the natural Man 5 and slightly exceeding the Man 9 epitope in blocking DC-SIGN binding to the SARS-CoV-2 spike protein. NMR binding epitope mapping and MD simulations confirmed preferential engagement of the α(1 → 3) branch and fluorine-dependent stabilization of local contacts. ITC studies indicated that enhanced binding arises from favorable enthalpic contributions, supported by both polar interactions and fluorination-driven desolvation. These results establish selective fluorination as a powerful strategy to boost lectin ligands affinity and generate potent glycomimetics for targeting DC-SIGN • Precise fluorination of Man 5 boosts DC-SIGN binding affinity • C-6 fluorination enhances, while C-2 reduces, lectin recognition • (6F,6F)-Man 5 surpasses Man 5 and slightly exceeds Man 9 in DC-SIGN inhibition • NMR & MD show α(1 → 3) branch engagement and fluorine-stabilized contacts • Enhanced binding is enthalpy-driven via polar interactions and desolvation.