Preparation of 1‐Ethynylpyrene‐Modified DNA via Sonogashira‐Type Solid‐Phase Couplings and Characterization of the Fluorescence Properties for Electron‐Transfer Studies

A range of 1‐ethynylpyrene‐modified oligonucleotides (Py−≡−dU) has been prepared by a special semi‐automated strategy using Sonogashira‐type cross‐coupling conditions in the solid phase. The absorption and fluorescence properties of the Py−≡−dU‐modified single strands and their corresponding double‐stranded duplexes have been characterized. The presented spectra show that the Py−≡−dU emission is quenched in DNA duplexes bearing a thymine or cytosine adjacent to the Py−≡−dU group. This shows that the Py−≡−dU moiety is able to inject an electron into the base stack while simultaneously acting as a spectroscopic label to enable the observation of these processes. Hence, Py−≡−dU‐modified oligonucleotides are promising donor systems in order to study electron injection and electron transport in DNA spectroscopically. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)