Synthesis and evaluation of keto-glutamine analogues as potent inhibitors of severe acute respiratory syndrome 3CLpro.

The 3C-like proteinase (3CL(pro)) of severe acute respiratory syndrome (SARS) coronavirus is a key target for structure-based drug design against this viral infection. The enzyme recognizes peptide substrates with a glutamine residue at the P1 site. A series of keto-glutamine analogues with a phthalhydrazido group at the alpha-position were synthesized and tested as reversible inhibitiors against SARS 3CL(pro). Attachment of tripeptide (Ac-Val-Thr-Leu) to these glutamine-based "warheads" generated significantly better inhibitors (4a-c, 8a-d) with IC(50) values ranging from 0.60 to 70 microM.