Fluorescent 2-Deoxyuridine (dU) Analogue: Tropolonyl triazolyl -dU ( tt -dU) Exhibits Solvatochromism/HeLa Cell Internalization and Its Triphosphate ( tt -dUTP) Is Incorporated into DNA Enzymatically

This era has witnessed the development and extensive application of modified nucleosides, including fluorescent nucleosides that clinically served humankind. Most fluorescent nucleoside analogues are derived from benzenoid aromatic scaffolds. However, the non-benzenoid aromatic moiety, tropolone, which exhibits unique hydrogen bonding and metal chelating properties, also occurs in nature. Recently, we introduced the tropolone unit at deoxyuridine through an ethyne linker and prepared its DNA analogues, which are fluorescent. This report describes the synthesis of a new troponyl triazolyl-dU (tt-dU) analogue, possessing a triazolyl linker, through click chemistry. tt-dU exhibits fluorescence with solvatochromism and enters into Hela cells without any cytotoxicity. Its triphosphate (tt-dUTP) was also synthesized and incorporated enzymatically into DNA, as shown in primer extension experiments. The unique photophysical properties and metalchelating ability of the tropolone group make tt-dU a promising modified nucleoside.