Oligonucleotides containing substituted 4-nitroindoles: Synthesis and study of their DNA duplexes

The synthesis of oligonucleotides containing 1-(2-deoxy-beta-D-ribofuranosyl)-2-methyl-4-nitroindole and 1-(2-deoxy-beta-D-ribofuranosyl)-2-phenyl-4-nitroindole is described. The synthesized modified oligonucleotides were used for studying the stability of intermolecular DNA duplexes with one unnatural strand and for evaluation of discriminating potential of 2-methyl- and 2-phenyl-4-nitroindoles toward nucleic bases. For comparison, an unmodified oligonucleotide and oligonucleotides bearing 5-nitroindole were used. It was shown that 2-methyl-4-nitroindole was only insignificantly inferior in stability to 5-nitroindole and characterized by a similar discriminating potential. 2-Phenyl-4-nitroindole provided a more pronounced duplex destabilization, the discrimination toward natural bases being decreased.