The Nε-protecting group Dde is orthogonal to both Fmoc and Boc which allows on-resin modification of lysine side chains during Fmoc/tBu-based SPPS. The applications of Dde side-chain protection include synthesis of branched or di-epitopic peptides, preparation of MAP core molecules and lipo-MAPS, the synthesis of cyclic peptides, TASP molecules, and templates for combinatorial chemistry and synthetic proteins. Dde can be cleaved by 2% hydrazine in DMF.