(1R,2S)-Ethyl 1-(tert-butoxycarbonylamino)-2-vinylcyclopropanecarboxylate is a chiral cyclopropane derivative. It serves as a crucial advanced intermediate in the synthesis of complex pharmaceutical agents. Its structure features a vinylcyclopropane core, a tert-butoxycarbonyl (Boc)-protected amino group, and an ethyl ester, making it a versatile building block for constructing conformationally constrained molecules. This compound is primarily employed in the synthesis of BILN 2061, a potent and selective macrocyclic inhibitor of the hepatitis C virus (HCV) NS3 protease. The chiral cyclopropane moiety is a key structural element that contributes to the inhibitor's binding affinity and metabolic stability. Its role is pivotal in constructing the macrocyclic scaffold of this class of antiviral drugs, highlighting its importance in medicinal chemistry for developing treatments against infectious diseases. As a high-value chiral intermediate, its synthesis and availability are of significant interest in process chemistry for scaling up antiviral drug candidates. Handling requires standard precautions for laboratory chemicals, with attention to its potential sensitivity.