Used in peptide synthesis as a protected amino acid derivative, particularly for introducing cysteine-like residues with modified sulfur functionality. The acetamidomethyl (Acm) group protects the thiol side chain, allowing selective deprotection and disulfide bond formation in complex peptide assembly. The Fmoc group enables solid-phase synthesis by providing orthogonal protection for the alpha-amino group, compatible with base-labile cleavage conditions. Commonly applied in the preparation of structured peptides requiring precise disulfide bridge pairing, such as in therapeutic peptides or cyclic peptide scaffolds.