Targeting Chikungunya virus entry: Enantiomeric separation, synthesis of derivatives, and structure-activity relationship of E1-E2 envelope glycoprotein inhibitors.

Chikungunya virus (CHIKV) remains a global health concern partly due to the lack of effective antiviral strategies to control its current global expansion. In this study, we report the design, synthesis, and biological evaluation of a novel series of small-molecule CHIKV entry inhibitors targeting the viral E1-E2 envelope glycoprotein complex. Starting from a previously identified racemic β-amino alcohol compound (1) with low micromolar antiviral activity, we performed enantiomeric separation, absolute configuration assignment, and biological evaluation of (R)-1 and (S)-1. Both enantiomers retained activity, with (S)-1 showing slightly greater potency (EC50 = 6 ± 1 μM) than (R)-1 (EC50 = 14 ± 4 μM). A library of 40 derivatives was synthesized to explore structure-activity relationships (SAR), focusing on four key regions: the amino/hydroxyl groups (AH), the piperidine core (PC), the left-hand side (LHS), and the right-hand side (RHS) of the molecule. SAR analysis revealed that the central piperidine scaffold and the hydrogen-bonding capability of the amino and hydroxyl groups were essential for antiviral activity. Bulky or strongly electron-withdrawing substituents on the RHS often increased cytotoxicity. In contrast, several LHS modifications enhanced potency or selectivity. In vitro ADME profiling of compound 1 and selected derivatives showed favorable chemical and plasma stability and moderate-to-high permeability in the PAMPA assay. However, solubility was limited under neutral conditions, anticipating the need of adequate formulation strategies for in vivo administration. Metabolic stability varied across the series, with certain derivatives showing resistance to CYP-mediated oxidation. These findings validate the CHIKV E1-E2 heterodimer as a promising antiviral target and identify a set of selective, stable, and synthetically tractable inhibitors suitable for further preclinical development.