Nα-p-Tosyl-L-lysine methyl ester hydrochloride is a protected derivative of L-lysine used as a building block in peptide synthesis. The p-tosyl group serves as a protecting group for the α-amino functionality, while the methyl ester protects the carboxylic acid group. This enables selective activation and coupling during the formation of peptide bonds, ensuring precise assembly of amino acid sequences. It is widely employed in the production of custom peptides for research in biochemistry and molecular biology. Its applications also include the development of peptide-based drugs and therapeutic agents, where accurate control of peptide structure is critical.