PEG-Supported Synthesis of Cyclic Oligodeoxyribonucleotides

Cyclic oligodeoxyribonucleotides have been synthesized in satisfactory yields by an easy procedure using polyethylene glycol (PEG) as soluble supporting polymer. The present method is particularly suitable for a medium to large scale synthesis. Early studies involving biological properties of synthetic1 and natural2 cyclic oligonucleotides stimulated a great deal of interest in such kind of molecules. The recent findings3 that circular single-stranded oligodeoxyribonucleotides having two runs of pyrimidines can bind tightly and sequence selectively to single-stranded polypurine DNA and RNA by forming triple helical complexes open up new perspectives to the design of more efficient DNA-and RNA-binding molecules. Our attention is being focused on the synthesis of medium-sized rings, since none of the synthetic procedures described so far proved to be really suitable for the preparation of such molecules on a relatively large scale. Following „classical“ solution methods, which in principle should easily allow syntheses