Z-Arg(Tos)-OH.CHA is a doubly protected form of the amino acid arginine, commonly used as a building block in peptide synthesis. The Z (benzyloxycarbonyl) group protects the α-amino group, while the tosyl (Tos) group serves as a protective moiety for the guanidine side chain, preventing side reactions during peptide coupling processes. This compound is especially valuable in solid-phase peptide synthesis (SPPS), enabling precise sequential addition of amino acids while maintaining the integrity of the arginine residue. Upon completion of the peptide chain, the protecting groups can be selectively removed under mild conditions to reveal the free arginine. Its use is essential in the synthesis of complex peptides for research, pharmaceutical development, and biotechnological applications.