Used in peptide synthesis as a protected amino acid building block for (S)-ornithine, particularly in solid-phase peptide synthesis (SPPS). The Fmoc group provides temporary protection for the alpha-amino group, allowing selective deprotection under mild basic conditions (e.g., with piperidine). The allyl ester protects the carboxylic acid and can be removed selectively using palladium(0) catalysis without affecting other protecting groups. The side chain amino group at the 5-position is unprotected and present as the hydrochloride salt, which enhances stability and solubility during handling. This allows for strategies where the side chain can be further modified or conjugated. Commonly employed in the stepwise assembly of complex peptides requiring orthogonal protection. Its chiral (S)-configuration ensures stereochemical control in the final peptide product.