A new synthetic approach to cyclic bis(3'-->5')diguanylic acid.

We developed a novel synthesis of biologically important cyclic bis(3'-->5')diguanylic acid (cGpGp). The present synthesis includes two strategies different from those employed in an existing synthesis. They are the phosphoramidite method for the preparation of a guanylyl(3'-->5')guanylic acid intermediate and allyl protection for guanine bases and internucleotide linkages. These distinctive strategies have allowed the new synthesis to provide the target compound in a higher yield than that of the existing synthesis.