The same research group disclosed a novel series of peptide inhibitors containing a decahydroisoquinoline moiety in place of P2‐cyclohexyl of 46 to reduce the peptidic nature of the inhibitors. A few examples (47–51) are shown in Figure 16. Among them, 49 was moderately more active against SARS‐CoV Mpro when compared to 46. 148  The X‐ray structure of Mpro in complex with 49 revealed that the P2‐decahydroisoquinoline moiety was fittingly placed in the S2‐subsite, while the P1‐imidazole moiety occupied the S1‐subsite. With these key residues located appropriately in their respective pockets, the terminal functional group fits tightly into the active site.