()-S-Trityl-L-cysteine is primarily used in peptide synthesis as a protecting group for the thiol functionality of cysteine. The trityl group effectively shields the thiol group from unwanted reactions during the synthesis process, ensuring the integrity of the peptide chain. Once the synthesis is complete, the trityl group can be selectively removed under mild acidic conditions, revealing the free thiol group for further modifications or for the formation of disulfide bonds, which are crucial for the structural stability of many proteins and peptides. Additionally, this compound is employed in the study of enzyme mechanisms and protein folding, where the protection and subsequent deprotection of cysteine residues are essential for understanding their roles in biological processes.