Dde-protected PNA monomers, orthogonal to Fmoc, for the synthesis of PNA–peptide conjugates

Peptide nucleic acids have become, arguably, one of the most interesting of DNA mimics. Herein the efficient solution phase synthesis of four novel 1-(4,4-dimethyl-2,6-dioxacyclohexylidene)ethyl/4-methoxytrityl (Dde/Mmt) protected PNA monomers is reported which were then used to synthesise PNA–peptide conjugates through a mild Dde deprotection strategy, which was fully orthogonal to Fmoc chemistry, allowing at will Fmoc peptide and Dde–PNA synthesis.