The present invention relates to compounds of Formula I, II or Ill, or a
pharmaceutically acceptable salt, ester, or prodrug, thereof:
##STR00001## 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.