New types of double-headed 2'-deoxycytidine 5'-0-triphosphates (dOcTPs) bearing another cytosine or 5-fluorocytosine linked through a flexible propargyl, homopropargyl or pent-1-ynyl linker to position 5 were prepared by the aqueous Sonogashira cross -coupling reactions of 5-iodo-dCTP with the corresponding (fluoro)cytosine-alkynes. The modified dCxcTPs were good substrates for DNA polymerases and were used for enzymatic synthesis of cytosine-functionalized DNA by primer extension or PCR.
The cytosine or fluorocytosine-linked DNA probes did not significantly inhibit DNA methyltransferases and did not cross-link to these proteins.