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 protects the amino group and the Mtt group protects the thiol side chain. This protection is crucial for the selective formation of peptide bonds, allowing for the controlled assembly of peptide chains. The Mtt group can be selectively removed under mild acidic conditions, enabling the subsequent formation of disulfide bonds or the introduction of other functional groups at the cysteine residue. This makes it valuable in the synthesis of complex peptides and proteins, especially those requiring precise disulfide bridge formation, such as in the production of therapeutic peptides, hormones, and enzymes. Its application is essential in research and pharmaceutical industries for developing biologically active peptides with specific structural and functional properties.