Selective covalent targeting of SARS-CoV-2 main protease by enantiopure chlorofluoroacetamide

The coronavirus disease 2019 (COVID-19) pandemic has necessitated the development of antiviral agents against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The main protease (M(pro)) is a promising target for COVID-19 treatment. Here, we report an irreversible SARS-CoV-2 M(pro) inhibitor possessing chlorofluoroacetamide (CFA) as a warhead for the covalent modification of M(pro). Ugi multicomponent reaction using chlorofluoroacetic acid enabled the rapid synthesis of dipeptidic CFA derivatives that identified 18 as a potent inhibitor of SARS-CoV-2 M(pro). Among the four stereoisomers, (R,R)-18 exhibited a markedly higher inhibitory activity against M(pro) than the other isomers. Reaction kinetics and computational docking studies suggest that the R configuration of the CFA warhead is crucial for the rapid covalent inhibition of M(pro). Our findings highlight the prominent influence of the CFA chirality on the covalent modification of proteinous cysteines and provide the basis for improving the potency and selectivity of CFA-based covalent inhibitors.