New oligonucleotide analogues based on morpholine subunits joined by oxalyl diamide tether

We report on the design, synthesis and some of the properties of the new oligonucleotide analogues based on morpholine nucleoside (MorB) subunits joined by an oxalyl diamide tether instead of a phosphate group. The synthetic strategy and oligomer design are optimized to easily obtain target substances without using protective groups. The dimers HOMorU-Ox-NHMorU, HOMorU-Ox-NHMorA, and uracil containing the hexamer HOMorU-(Ox-NHMorU)5 were synthesized. The structures of all substances were confirmed by 1H, 13C, NMR, and mass spectroscopy. Base stacking interactions in dimers were revealed by CD-spectra data.