Used in organic synthesis as a protected amino acid derivative, particularly in peptide coupling reactions where selective protection of functional groups is required. Its Z-protected amine group allows for controlled deprotection under mild conditions, making it valuable in the stepwise construction of complex peptides. The osu ester (pentafluorophenyl or similar active ester) enhances reactivity toward nucleophiles, facilitating efficient amide bond formation with minimal racemization. Commonly employed in solid-phase and solution-phase peptide synthesis for pharmaceutical and biochemical research.