Boc-Cys(tBu)-OH is widely used in peptide synthesis as a protecting group for cysteine residues. The Boc (tert-butyloxycarbonyl) group safeguards the amino group, while the tBu (tert-butyl) group protects the thiol side chain of cysteine, preventing unwanted reactions during peptide chain assembly. This compound is particularly valuable in solid-phase peptide synthesis (SPPS), where selective deprotection allows for the controlled formation of disulfide bonds, crucial for the correct folding and function of many peptides and proteins. Its stability under various reaction conditions makes it a reliable choice for constructing complex peptide structures, especially in the production of therapeutic peptides and biochemical research.