Highly fluorescent 2‐Aminopurine derivatives: synthesis, photo‐physical characterization, and preliminary cytotoxicity evaluation

Abstract

New fluorescent nucleobase analogues (FBAs) are emerg-ing as extraordinarily useful tools for DNA labelling tech-nologies. The highly fluorescent adenine analogue 2 aminopurine (2AP) is still the most used within the few hundreds of newly FBAs synthesized, but its excitation in the UV region demands for high energy sources endanger-ing living cells. New and highly fluorescent 2AP deriva-tives, 2-amino-6-cyanopurines, were obtained using novel, simpler, but very efficient synthesis method. All the new compounds exhibit advantageous photophysical properties over 2AP, showing absorption and emission bands ranging the visible region (blue-green region), high fluorescence quantum yields and Stokes’ shifts, especially in non-protic organic solvents. Density Functional Theory calculations (DFT) of electronic and vibrational structure were per-formed, allowing to predict absorption and emission spec-tra in accordance with experimental data. The extensive solvatochromism of compounds gives them important microenvironmental sensitivity to be used as superior fluorescent probes, comparing to 2AP. In addition, these newly synthesized 2-amino-6-cyanopurines exhibit little to no toxicity in assays using yeast cells, making them also valuable candidates for fluorescent studies in living cells.