Synthesis and Characterization of the Diastereomers Λ‐ and Δ‐[Ru(bpy) 2 (m‐bpy‐Gly‐ L ‐His‐ L ‐Lys)]Cl 2 − 1 H NMR Studies on Their Interactions with the Deoxynucleotide Duplex d[(5′‐CGCGAATTCGCG‐3′) 2 ]

The synthesis and characterization of the diastereomeric complexes Λ‐ and Δ‐[Ru(bpy) 2 (m‐bpy‐GHK)]Cl 2 , (GHK = glycine‐ L ‐histidine‐ L ‐lysine, m‐bpy = 4′‐methyl‐2,2′‐bipyridine) as well as their binding properties to the deoxynucleotide duplex d(5′‐CGCGAATTCGCG‐3′) 2 studied by means of NMR, ESI‐MS and CD spectroscopy, are reported. The ROESY spectrum of Λ‐[Ru(bpy) 2 (m‐bpy‐GHK)]Cl 2 shows intramolecular cross peaks between the bpy H3 or H3′ protons and the aromatic H2 and H5 of the histidine imidazole ring, indicating that the peptide adopts an orientation with the imidazole ring close to the bpy ligand, possibly interacting by π‐stacking. The absence of intramolecular cross peaks between the peptide and the bipyridine ligands in the ROESY spectrum of Δ‐[Ru(bpy) 2 (m‐bpy‐GHK)]Cl 2 on the other hand, shows that in this case the peptide is far from the two bpy ligands, having a different orientation from the Λ isomer. The isomers interact with the oligonucleotide duplex differently. Δ‐[Ru(bpy) 2 (m‐bpy‐GHK)]Cl 2 binds in the oligonucleotide major groove close to the central part of the sequence. Λ‐[Ru(bpy) 2 (m‐bpy‐GHK)]Cl 2 binds, probably non selectively, approaching the helix from the minor groove. It can be concluded that the peptide (GHK) binding leads the rest of the isomer to interact with the oligonucleotide in the case of the Δ isomer. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)