Used in solid-phase peptide synthesis to introduce a protected diaminobutyric acid residue with orthogonal protection. The Dnp (dinitrophenyl) group acts as a protecting group for the side-chain amine, which can be selectively removed under mild conditions using thiols, allowing stepwise construction of complex peptides. The Fmoc group protects the alpha-amine and is removed with piperidine, enabling sequential coupling in automated synthesis. Commonly applied in the preparation of branched peptides, peptide dendrimers, and bioconjugates where precise side-chain manipulation is required. Also useful in the synthesis of peptide-based probes and enzyme substrates due to the selective deprotection capability.