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Synthesis and Biochemical Characterization of Tricyclothymidine Triphosphate (tc‐TTP)

Tricyclo‐DNA (tc‐DNA) is a conformationally restricted oligonucleotide analogue that exhibits promising properties as a robust antisense agent. Here we report on the synthesis and biochemical characterization of tc‐TTP, the triphosphate of a tc‐DNA nucleoside containing the base thymine. Tc‐TTP turned out to be a substrate for the Vent (exo−) DNA polymerase, a polymerase that allows for multiple incorporations of tc‐T nucleotides under primer extension reaction conditions. However, the substrate acceptance is rather low, as also observed for other sugar‐modified analogues. Tc‐TTP and tc‐nucleotide‐containing templates do not sustain enzymatic polymerization under physiological conditions; this indicates that tc‐DNA‐based antisense agents will not enter natural metabolic pathways that lead to long‐term toxicity.