The present invention relates to compounds of Formula I, II or Ill, or a pharmaceutically acceptable salt, ester, or
prodrug, thereof: wherein W is a substituted or unsubstituted heterocyclic ring
system. The compounds inhibit
serine protease activity, particularly the activity of
hepatitis c
virus (HCV) NS3-NS4A
protease. Consequently, the compounds of the present invention interfere with the life cycle of the
hepatitis c
virus and are also useful as antiviral agents. The present invention further relates to pharmaceutical compositions comprising the aforementioned compounds for administration to a subject suffering from HCV infection. The invention also relates to methods of treating an HCV infection in a subject by administering a pharmaceutical composition comprising the compounds of the present invention.