Résumé
We describe the different approaches towards the introduction of conformationally constraints into nucleic acids by means of cyclic phospho di- or triester in order to produce biological relevant structure mimics. Constraints along the sugar-phosphate backbone were first introduced by synthesis of macrocyclic structures. By use of the Ring-Closing Metathesis, medium size cyclic phosphotriester rings were reached. Finally, dioxaphosphorinane rings were introduced at key position along the sugar-phosphate backbone allowing the control of the six torsion angles.