Nucleoside Phosphoramidites

Nucleoside phosphoramidites are derivatives of natural or synthetic nucleosides and are used to synthesize oligonucleotides, relatively short fragments of nucleic acid and their analogs. Nucleoside phosphoramidites were first introduced in 1981 by Beaucage and Caruthers. These nucleoside phosphoramidites permit the sequential addition of new bases to the DNA chain in an exquisitely simple and exceptionally efficient cyclic reaction. A standard phosphoramidite molecule contains a phosphite instead of the typical phosphate in nucleotides, as well as four specific protecting groups. These groups provide stable protection, but can be easily removed when necessary.