The methods for the synthesis and purification of negatively charged peptide nucleic acid (PNA)-relative deoxyribonucleic acid (DNA) mimics containing alternating residues of phosphono peptide nucleic acid (pPNA) monomers and PNA-like monomers on the base of trans -4-hydroxy-L -proline are described. Examples of the chimeric oligomers hybridization with complementary DNA and ribonucleic acid fragments are demonstrated.