Synthesis, modification and docking studies of 5-sulfonyl isatin derivatives as SARS-CoV 3C-like protease inhibitors

The Severe Acute Respiratory Syndrome (SARS) is a serious life-threatening and strikingly mortal respiratory illness caused by SARS-CoV. SARS-CoV which contains a chymotrypsin-like main protease analogous to that of the main picornavirus protease, 3CLpro. 3CLpro plays a pivotal role in the viral replication cycle and is a potential target for SARS inhibitor development. A series of isatin derivatives as possible SARS-CoV 3CLpro inhibitors was designed, synthesized, and evaluated by in vitro protease assay using fluorogenic substrate peptide, in which several showed potent inhibition against the 3CLpro. Structure-activity relationship was analyzed, and possible binding interaction modes were proposed by molecular docking studies. Among all compounds, 8k1 showed most potent inhibitory activity against 3CLpro (IC50 = 1.04 μM). These results indicated that these inhibitors could be potentially developed into anti-SARS drugs.