Synthesis of a ferrocenyl uracil PNA monomer for insertion into PNA sequences

The deprotection of the tert-butyl group of a ferrocenyl uracil Peptide Nucleic Acid (PNA) monomer, Fmoc-aeg(R)-OtBu (1) was achieved using a two step synthesis involving hydrolysis in basic conditions to give first the zwitterion of +NH3-aeg(R)-O− (7). Compound 7 was reacted in situ with N-(9-fluorenylmethoxycarbonyloxy)succinimide to obtain the expected compound Fmoc-aeg(R)-OH (2) (Abbreviations: Aeg = (2-aminoethyl)-glycine; Fmoc = 9-fluorenylmethoxycarbonyl; OtBu = tert-butyl; R = 5-(N-ferroce-nylmethylbenzamido)uracyl).