7-Deazapurine Oligodeoxyribonucleotides: The Effects of 7-Deaza-8-methylguanine on DNA Structure and Stability

Article abstract of DOI:10.1002/hlca.19980810310

Oligodeoxyribonucleotides containing 7-deaza-2′-deoxy-8-methylguanosine (m⁸c⁷G_d; 2b) were prepared. For this purpose, the phosphonate 3a and the phosphoramidite 3b were synthesized and employed in solidphase oligodeoxyribonucleotide synthesis. The structures and the thermodynamic data of duplex formation of oligodeoxyribonucleotides containing 2b were investigated by temperature-dependent CD and UV spectra and compared with those containing 7-deaza-2′-deoxy-7-methylguanosine (m⁷c⁷G_d) or 7-deaza-2′-deoxy-guanosine (c₇G_d; 2a). In general, compound 2b reduces the duplex stability. In case of the sequence d(m⁸c⁷G-C)₄ (18), the B → Z transition was facilitated by the incorporation of 2b. Moreover, a single 7-deaza-8-methylguanine residue present in an oligodeoxyribonucleotide tract of guanine residues destabilizes the dG quadruplex significantly. This destabilization is more pronounced than in the case of 7-deazaguanine or 7-deaza-7-methyl-guanine.