Convergent Solution Phase Synthesis of Chimeric Oligonucleotides by a 2+2 and 3+3 Phosphoramidite Strategy

A chimeric oligonucleotide tetramer and hexamer were synthesized by the phosphoramidite approach using a 2+2 and 3+3 strategy, respectively. The concept of convergent synthesis provides an efficient route toward the synthesis of longer chimeric oligonucleotides, such as small interfering RNA oligonucleotides without the pollution of n - 1 or shorter failures. This methodology offers an efficient and economical way to scale-up the synthesis of high purity oligonucleotides for clinical trials and commercial uses.