Used primarily in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS) methods. It serves as a protected form of cysteine, where the Fmoc group safeguards the amino group, and the methyl group protects the thiol side chain. This protection is crucial to prevent unwanted side reactions during the peptide assembly process. It is especially valuable in synthesizing peptides containing cysteine residues, ensuring correct folding and disulfide bond formation. Commonly applied in the production of therapeutic peptides, research peptides, and bioconjugates, where precise control over cysteine reactivity is essential.