Used in peptide synthesis and medicinal chemistry as a protected cysteine derivative. Serves as an intermediate in the preparation of protease inhibitors, particularly for viral targets such as hepatitis C and SARS-CoV-2 main protease. The acetylthio and sulfamoyl groups enable selective deprotection and conjugation, making it valuable in developing covalent inhibitors. Its stereochemistry supports high selectivity in enzyme binding, enhancing drug potency and metabolic stability.