Simple and rapid procedure for synthesis of deoxynucleoside 3'-2-cyanoethyl-N,N-diisopropyl-amino phosphites

2-Cyanoethyl-bis/N,N-diisopropyl/phosphoamidite can be prepared from PCl3 by a very fast and efficient procedure. Without purification it was used for the phosphitilation of suitably protected deoxynucleosides which after simple purification are obtained with a high yield, in a stable and easy to manage form.