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Base‐Pairing Systems Related to TNA Containing Phosphoramidate Linkages: Synthesis of Building Blocks and Pairing Properties

As part of a project that aims at screening TNA‐related oligonucleotide systems in which threose backbone units may have some or all of their oxygen functions replaced by nitrogen, two TNA analogs containing (2′NH)‐ and (3′NH)‐phosphoramidate groups, respectively, in place of phosphodiester groups were synthesized. They show base‐pairing properties that are very similar to those of TNA itself. We also synthesized 2′,3′‐diamino analogs of α‐L‐threofuranosyl mononucleosides, yet attempts to convert them to TNA analogs containing phosphodiamidate linker groups were not successful. Such 2′,3′‐diamino derivatives of threofuranosyl nucleosides may be of interest, however, as building blocks of TNA analogs that contain non‐phosphorous linker groups.