Design, Synthesis, and Biological Evaluation of Peptidomimetic Tetrahydropyrrole Spirodihydroindolones as SARS-CoV-2 3CL Protease Inhibitors.

The 3CL protease (3CLpro) of SARS-CoV-2 is a key enzyme that plays an essential role in mediating viral replication and transcription. In this study, we synthesized and evaluated a series of peptidomimetic compounds containing a tetrahydropyrrole spirodihydroindolone moiety. Among the target compounds, 13c and 17d exhibited obvious 3CLpro inhibitory activities with IC50 = 3.71 and 6.21 nM, respectively. In metabolic stability testing of liver microsomes, compound 13c showed improved stability in human liver microsomes. In addition, 13c displayed significant anti-SARS-CoV-2 activity and high safety in Vero E6 cells (EC50 = 19.26 nM, SI > 400). Further investigations indicated that 13c showed potent activity against HCoV-OC43 and favorable safety in Huh7 cells (EC50 = 61 nM, SI > 100). These findings suggest that compound 13c is a promising lead compound in the development of novel 3CLpro inhibitors.