1R,3S,5R)-2-(tert-Butoxycarbonyl)-2-azabicyclo[3.1.0]hexane-3-carboxylic Acid acts as a reagent in the preparation of fused bicycles end-capped with peptide derivatives as HCV inhibitors. Synthesis of (tert-butoxycarbonyl)azabicyclohexanecarboxylic acid via stereoselective cyclopropanation of pyrroline