Synthesis of polyamide nucleic acids (PNAs) using a novel Fmoc/Mmt protecting-group combination

The preparation of 9-Fluorenylmethoxycarbonyl(Fmoc) protected building blocks for the synthesis of polyamide nucleic acids (PNAs) is described. Use of 4-Methoxyphenyldiphenylmethyl (Mmt)-protecting groups for the exocyclic amino function of the nucleobases enhances the solubility of the monomers and allows final deprotection by mild acid treatment. The novel synthetic route is exemplified by the synthesis of heptameric and octameric PNAs.