Diene-modified nucleotides for the Diels-Alder-mediated functional tagging of DNA.

We explore the potential of the Diels-Alder cycloaddition for the functional tagging of DNA strands. A deoxyuridine triphosphate derivative carrying a diene at position 5 of the pyrimidine base was synthesized using a two-step procedure. The derivative was efficiently accepted as substrate in enzymatic polymerization assays. Diene carrying strands underwent successful cycloaddition with maleimide-terminated fluorescence dyes and a polymeric reagent. Furthermore, a nucleotide carrying a peptide via a Diels-Alder cyclohexene linkage was prepared and sequence-specifically incorporated into DNA. The Diels-Alder reaction presents a number of positive attributes such as good chemoselectivity, water compatibility, high-yield under mild conditions and no additional reagents apart from a diene and a dienophile. Furthermore, suitable dienophiles are commercially available in the form of maleimide-derivatives of fluorescent dyes and bioaffinity tags. Based on these advantages, diene- and cyclohexene-based nucleotide triphosphates are expected to find wider use in the area of nucleic acid chemistry.