Design and synthesis of spiro-cyclopentenyl and spiro-[ and ]-dithiolanyl substituted pyrrolidine-5,5-trans-lactams as inhibitors of hepatitis C virus NS3/4A protease

Using the pyrrolidine-5,5-trans-lactam template, we have designed small, neutral, mechanism-based inhibitors of hepatitis C NS3/4A protease. Compound 2b, with a spiro-cyclobutyl P1 substituent and an isopropyl carbonyl substituent at the lactam nitrogen, has an IC50 value in the replicon cell-based assay of 3 μM.