This compound is widely used in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS). It serves as a protected form of cysteine, where the Fmoc (fluorenylmethyloxycarbonyl) group protects the amino group, and the STBU (tert-butylsulfanyl) group protects the thiol side chain of cysteine. This protection is crucial to prevent unwanted side reactions during the peptide assembly process. The compound is especially valuable in synthesizing peptides that contain cysteine residues, which are prone to oxidation and disulfide bond formation. Its application is essential in producing peptides for research, pharmaceuticals, and biotechnology, where precise control over cysteine incorporation is required. Additionally, it enables the synthesis of complex peptides with specific disulfide bond patterns, which are often critical for biological activity.