Discovery of the HCV NS3/4A Protease Inhibitor (1R,5S)-N-3-Amino-1-(cyclobutylmethyl)-2,3-dioxopropyl-3- 2(S)-[[[(1,1-dimethylethyl)aminocarbonyl]amino]-3,3-dimethyl-1-oxobutyl]- 6,6-dimethyl-3-azabicyclo3.1.0hexan-2(S)-carboxamide (Sch 503034) II. Key Steps in Structure-Based Optimization