Used in peptide synthesis as a protected form of cysteinol, enabling selective disulfide bond formation in complex peptides. The Boc group provides temporary N-terminal protection, while the p-methylbenzyl (pMeBzl) side-chain protecting group stabilizes the thiol functionality during solid-phase or solution-phase synthesis. This derivative is particularly valuable in the preparation of therapeutic peptides and cyclic structures where precise control over folding and oxidation is required. Its stability under acidic conditions and clean deprotection profile make it suitable for multi-step syntheses in pharmaceutical development.