Used in solid-phase peptide synthesis, particularly for the preparation of complex peptides requiring selective side-chain protection. The Dde (1-(4,4-dimethyl-2,6-dioxocyclohex-1-ylidene)ethyl) group allows for orthogonal protection of the side-chain amine, which can be selectively removed with hydrazine under mild conditions without affecting the Boc (tert-butoxycarbonyl) group. This enables stepwise assembly of peptides with multiple lysine or other amino groups, where selective deprotection is needed. Commonly applied in the synthesis of branched peptides, peptide dendrimers, and protein mimics, especially in research involving epitope-specific antibodies or multivalent ligands. Its D-configuration makes it useful in designing metabolically stable peptide analogs or enzyme inhibitors.