Abstract
The chemical synthesis of peptide nucleic acid (PNA) monomers is described using Fmoc (backbone), anisoyl (cytosine, adenine), 4-tert-butylbenzoyl (cytosine) and isobutyryl/diphenylcarbamoyl (guanine) protecting group combinations. For the guanine monomer the alkylation was realized both in a Mitsunobu [DIAD, triphenylphosphine or (4-dimethylaminophenyl)diphenylphosphine, tert-butyl glycolate] and in a low-temperature, sodium-hydride mediated alkylation (tert-butyl bromoacetate) to give the N9 -substituted derivative.