The present invention relates to peptidomimetic compounds useful as protease inhibitors, particularly as serine protease inhibitors and more particularly as hepatitis C NS3 protease inhibitors; intermediates thereto; their preparation including novel stereoselective processes to intermediates. The invention is also directed to pharmaceutical compositions and to methods for using the compounds for inhibiting HCV protease or treating a patient suffering from an HCV infection or physiological condition related to the infection. Also provided are pharmaceutical combinations comprising, in addition to one or more HCV serine protease inhibitors, one or more interferons exhibiting anti-HCV activity and/or one or more compounds having anti HCV activity and a pharmaceutically acceptable carrier, and methods for treating or preventing a HCV infection in a patient using the compositions. The present invention is also directed to a kit or pharmaceutical pack for treating or preventing HCV infection in a patient.