Used in peptide synthesis as a protected lysine derivative, enabling selective amino group protection during solid-phase or solution-phase peptide assembly. The 4-nitro-Z group provides orthogonality with other protecting groups, allowing stepwise construction of complex peptides. Commonly applied in the production of pharmaceutical intermediates and bioactive peptides where precise side-chain protection is required. Stable under acidic conditions but removable under mild reducing conditions, making it suitable for multi-step syntheses.