Uridine-Conjugated Ferrocene DNA Oligonucleotides:  Unexpected Cyclization Reaction of the Uridine Base

The study of energy and electron-transfer processes through DNA duplexes and the development of DNA hybridization probes and electrochemical sensors have resulted in the incorporation of numerous transition-metal complexes into DNA oliognucleotides. These include ruthenium, osmium, iron, rhodium, and copper complexes. Ferrocene (Fc) and its derivatives are attractive electrochemical probes because of their stability and convenient synthetic chemistry. Fc-containing DNA oligonucleotides have been prepared by attaching ferrocenyl moieties to the 5‘ termini through either solid-phase synthesis using phosphoramidites or by reacting suitable ferrocenyl derivatives with end-functionalized oligonucleotides.