Used in solid-phase peptide synthesis, particularly for the preparation of complex peptides requiring selective side-chain protection. The Dde group protects the side-chain amine of the diaminopropionic acid residue and can be removed orthogonally to other protecting groups like Boc, allowing stepwise assembly of multi-functional peptides. This makes it valuable in synthesizing branched or modified peptides, such as those used in drug development, epitope mapping, and bioconjugation. Its selective deprotection under mild conditions (e.g., with hydrazine) enables site-specific modifications without affecting other parts of the molecule.