The delivery of DNA/RNA therapeutic drugs is still a major hurdle for the clinical application of DNA/RNA-based drugs. Also, developments in silencing the expression of specific genes, through RNA interference pathways, have led to an increased demand for synthetic RNA sequences and have created a pressing need for rapid and efficient methods for RNA synthesis. Recently, FDA scientists have developed a novel phosphoramidite, 2?-O-aminooxymethyl ribonucleoside (2?-O-protected compounds). The 2?-O-aminooxymethyl ribonucleoside can be modified with any type of functional group using an oximation reaction as long as the functional group contains an aldehyde, ketone, or acetal group. Modification of the 2?-O-aminooxymethyl with an aldehyde results in a conjugated 2?-phosphoramidite that could be readily converted back to the native ribonucleoside and its corresponding by-product. On the other hand, the oximation of 2?-O-aminooxymethy with a ketone results in an irreversible conjugated form of the phosphoramidite. 0 

The 2?-O-protected compounds of the present technology have several advantages, for example, the 2?-O-protected compound is stable during the various reaction steps involved in oligonucleotide synthesis; and the protecting group can be easily removed after the synthesis of the oligonucleotide, for example, by reaction with tetrabutylammonium fluoride; and the O-protected groups do not generate DNA/RNA alkylating side products, which have been reported during removal of 2?-O-(2-cyanoethyl)oxymethyl or 2?-O-[2-(4-tolylsulfonyl)ethoxymethyl groups under similar conditions. 0