Synthetic Incorporation of Metal Complexes into Nucleic Acids and Peptides Directed toward Functionalized Molecules

Novel synthetic approaches for incorporation of metal complexes into nucleic acids and peptides are described. First, novel artificial β-C-nucleosides bearing a chelator nucleobase (2-aminophenol, catechol, or o-phenylenediamine) have been synthesized. These artificial nucleobases were introduced for alternative base pairing through metal coordination instead of the hydrogen bonding in natural DNA. 1H NMR and mass spectral studies clearly showed that o-phenylenediamine-type nucleoside forms a stable 2 : 1 square-planar complex with a PdII ion, providing an alternative DNA base pairing through metal complexation. Secondly, an efficient strategy for the liquid-phase synthesis of cyclic metallopeptides having a repeating Gly-L-Cys(terpyPtII) sequence, cyclo[-Gly-L-Cys(terpyPtII)-]nCln (n = 3, 4), has been developed. These cyclic metallopeptides were obtained by cyclization of the corresponding linear peptides, H2[-Gly-L-Cys(terpyPtII)-]nOH·(CF3CO2)n+1 (n = 3, 4), in moderate yields. The former cyclic hexapeptide was found to act as a positively charged anion receptor. This synthetic approach would provide a powerful tool for arraying metal centers on cyclopeptide frameworks.