Synthesis of the first ferrocene-labeled dideoxynucleotide and its use for 3'-redox end-labeling of 5'-modified single-stranded oligonucleotides

The target ferrocene-labeled dideoxynucleotide compound 5-N-(beta-ferrocenyl-propanoyl)3-amino-propyn-1-yl]-2',3'-dideoxyuridine 5'-triphosphate, Fc-ddUTP, was synthesized and tested with terminal deoxynucleotidyl transferase for enzymatic 3'-redox-active end-labeling of 5'-phosphorylated single-stranded oligodeoxynucleotides. Starting from readily available 5-iodouridine and 3-ferrocenylpropanoic acid, the synthetic strategy elaborated here follows a mild multistep route. Each step involves reliable methods, and all ferrocene intermediates can be easily purified. Enzymatic 3'-ferrocene end-labeling of 5'-phosphorylated oligonucleotides is remarkably efficient, and 3'-ferrocene-labeled oligonucleotides can thus be prepared in sufficient amounts for further use in surface modifications.