Abstract Three chimeric dimer synthons (oeg_tNHT, oeg_upNHT and oeg_uhNHT) containing thymine (t), 5-(l-propynyl)-uracil (up) and 5-(1-hexyn-1-yl)-uracil (uh) PNA units with N-(2-hydroxyethyl) glycine (oeg) backbone were synthesized in solution and incorporated into T20 oligonucleotide analogues, using standard P-amidite chemistry. Insertion of dimer blocks led to destabilization of duplexes with dA20 target. The smallest ...