A Straightforward Solid‐Phase Synthesis of Cyclic Oligodeoxyribonucleotides

For possible use as antisense or antigene therapeutic agents, fairly pure crude cyclic oligonucleotides can easily be prepared by solid-phase synthesis (see below). After cyclization with formation of a phosphotriester (a) and cleavage (b), all noncyclized compounds, polymers, and other impurities are removed by filtration (c).