An efficient synthesis of enantiomerically pure Delta- and Lambda-ruthenium(II)-labelled oligonucleotides

The synthesis of a novel tris(bidentate ligand)ruthenium(II) complex 7 and its efficient tethering to the 5'-end of oligonucleotides is described. The resulting Delta- and Lambda-isomeric ruthenium(II)-Iabelled oligonucleotides 10a-c and 11a-d were separated either by reversed-phase HPLC or by polyacrylamide gel electrophoresis. The diastereoisomerically pure isomers were fully characterized by UV/VIS and CD spectroscopy, mass spectrometry, and enzymatic digestion with base analysis. We also investigated the thermal denaturation of the hybridized double strands.