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The release of nucleobases from oligonucleotides (12-mer, d(5′-CGCTTTAAAGCG)2, 8-mer, d(5′-AAACGTTT)2, 7-mer, d(TCGCGCG)2, and 6-mer, d(CGCGCG)2) by copper(II) complex and hydrogen peroxide systems was investigated in terms of HPLC. The [Cu(bdpg)Cl]Cl complex gave a large quantity of free nucleobases in the reaction mixture, but the activities of other compounds, such as [Cu(tpa)Cl]ClO4, were much lower than that of the (bdpg)-complex; where (bdpg) and (tpa) represent a N,N-bis(2-pyridylmethyl) derivative of β-alanineamide and 2-aminomethylpyridine, respectively. The above results and the electrospray mass spectral data on the solutions strongly suggest that the remarkable activity of the (bdpg)-compound is due to the high electrophilic nature of the copper(II)–hydroperoxide adduct, whose formation is greatly promoted through hydrogen bonding with the amide-oxygen atom coordinated to the copper(II) atom, and this electrophilic copper(II)–peroxide adduct attacks the sugar ring of nucleoside, to give the corresponding hydroxylated species, and from which free nucleobases are released. |
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