Abstract
We newly designed and synthesized a 2 ′-deoxy type trans-3′,4′-bridged nucleic acid (trans-3′,4′-BNA) analogues bearing a 4,7-dioxabicyclo[4.3.0]nonane structure. The synthesis of the trans-3′,4′-BNA was carried out successfully from thymidine over 21 steps. The structure of trans-3′,4′-BNA was confirmed by x-ray crystallographic analysis, indicating that the furanose ring has a typical S-type conformation with C3′-exo puckering.