Ferrocenyl GNA Nucleosides: A Bridge between Organic and Organometallic Xeno-nucleic Acids

The enantioselective synthesis and electrochemistry of the first ferrocenyl GNA nucleosides is reported. These compounds were obtained by a Sharpless asymmetric dihydroxylation reaction of [3‐(N1‐thyminyl)‐1‐(ferrocenyl)]propene as S,R and R,S enantiomers in about 70 % yield with enantiomeric excesses of >99 % and 71 %, respectively. The absolute configurations of the chiral carbon atoms in the nucleosides were assigned by single‐crystal X‐ray diffraction analysis of the methyl derivatives in the solid state. The compounds were also studied with circular dichroism (CD) spectroscopy in solution. The enantiomeric relationship between the S,R and R,S isomers was confirmed by the near‐mirror‐image CD spectra. The redox properties of the nucleosides and their methylated derivatives were investigated using cyclic voltammetry. The cyclic voltammograms revealed reversible redox processes for the entire series of compounds at potentials of −25 mV (for nonmethylated derivatives) and 75 mV (for methylated derivatives) versus the ferrocene/ferrocenium reference redox couple.