[Synthesis of steroid-containing oligonucleotides and their alkylating derivatives].

New alkylating derivatives of oligonucleotides carrying a steroid (cholesterol, testosterone or ergosterol) residue have been synthesized, the residue being introduced via its hydroxyl group into the triester oligonucleotide block in the presence of triisopropylbenzenesulphonyl chloride and N-methylimidazole. Covalent attachment of steroids to oligonucleotides increases their hydrophobicity and does not influence the melting temperature of their complementary complexes. The data obtained showed that the oligonucleotide derivatives, bearing both an alkylating group of nitrogen mustard and a steroid residue, can be used as reagents for specific modification of nucleic acids.