A new approach to oligonucleotide N3′ → P5′ phosphoramidate building blocks

A new synthetic approach to 5′-phosphoramidites of 3′-aminonucleosides was developed. The methodology relies upon the use of 3′-amino-2′,3′-dideoxynucleosides as the key starting materials. The final products were obtained in high yields via 2–3-step processes using selective introduction of orthogonal protective groups to the 3′-aminonucleoside sugar and base moieties.