Synthesis of 2′-Deoxyuridineand 2′-Deoxycytidine Nucleosides Bearing Bipyridineand Terpyridine Ligands at Position 5

A methodology for the syntheses of pyrimidine (C or U) 2-deoxyribonucleosidesbearing bipyridine or terpyridine ligands attached via acetyleneor phenylene linkers was developed based on single step cross-couplingreactions of unprotected 5-iodopyrimidine nucleosides with bipyridineor terpyridine acetylenes of phenyl boronates. The Sonogashira reactionswith acetylenes were performed in DMF, while the Suzuki reactionswith boronates in water--acetonitrile mixtures.Photophysical properties of the title modified nucleosides havebeen studied and (2,2′-bipyridin-5-yl)ethynyl or (2,2′-bipyridin-5-yl)phenylderivatives exerting absorption at >300 nm and bright emissionat 421-451 nm were selected as the best candidates forluminescent DNA labeling.