Synthesis of 3-(2-deoxy-β-d-ribofuranosyl)pyridin-2-one and 2-amino-6-(N,N-dimethylamino)-9-(2-deoxy-β-d-ribofuranosyl)purine derivatives for an unnatural base pair

An unnatural base pair, 2-amino-6-(N,N-dimethylamino)purine (denoted x) and pyridin-2-one (denoted y), was designed to prove the structural requirements for base pair formation involving shape complementarity. It was expected that y might satisfy the structural requirements for pairing with x, in which the bulky 6-dimethylamino group may eliminate base pairing with the natural bases. As chemical or biological substrates for DNA synthesis, the phosphoramidite of x and the 2′-deoxy-C3-ribonucleoside triphosphate of y (dyTP) were synthesized, and the incorporation experiment was demonstrated by using the Klenow fragment of Escherichia coli DNA polymerase I.