Compounds of the formula (F) where the variables are as defined in thespecification inhibit the NS3 protease of flavivirus sych as hepatitis C virus(HCV). The compounds comprise a novel linkage between a heterocyclic P2 unitand those portions of the inhibitor more distal to the nominal cleavage siteof the native substrate, which linkage reverses the orientation of peptidicbonds on the distal side relative to those proximal to the cleavage site.