Nucleosides and Nucleotides. 204. Synthesis of Oligodeoxynucleotides Containing 6‘α-[N-(Aminoalkyl)carbamoyloxy]-carbocyclic-thymidines and the Thermal Stability of the Duplexes and Their Nuclease-Resistance Properties

To construct the nuclease-resistant oligodeoxynucleotides (ODNs) with natural phosphodiester linkages, we synthesized ODNs that contain 6‘α-[N-(aminoalkyl)carbamoyloxy]-carbocyclic-thymidines (4, 5, and 6). The stability of these ODNs to nuclease hydrolysis was examined by using snake venom phosphodiesterase (3‘-exonuclease) and nuclease S1 (endonuclease). It was found that the ODNs containing 4, 5, or 6 were more resistant to both the enzymes than the unmodified ODN. These nuclease-resistant properties are noteworthy, since they have natural phosphodiester linkages. Next, the thermal stabilities of duplexes consisting of these ODNs and either the complementary DNA or RNA were studied by thermal denaturation. The ODNs that contain 4 were found to enhance the thermal stability of the duplexes with the complementary DNA, while those containing 5 or 6 decreased the thermal stability of the ODN−DNA duplexes. On the other hand, all ODNs that contained 4, 5, or 6 decreased the thermal stability of the ODN−RNA duplexes.