New Zwitter-Ionic Oligonucleotides: Preparation and Complementary Binding

New zwitter-ionic oligonucleotide derivatives containing 1,2,3,4-tetrahydroisoquinoline-7-sulfonyl phosphoramidate group are described. Automated synthesis of these compounds was carried out according to the β-cyanoethyl phosphoramidite scheme via the Staudinger reaction between 2-trifluoroacetyl-1,2,3,4-tetrahydroisoquinoline-7-sulfonyl azide and phosphite triester within oligonucleotide grafted to polymer support. 1,2,3,4-Tetrahydroisoquinoline-7-sulfonyl phosphoramidate group (THIQ) was stable under the conditions of standard oligonucleotide synthesis, including the removal of protective groups and cleavage of the oligonucleotide from the polymer support by treatment with a mixture of concentrated aqueous solutions of ammonia and methylamine (1 : 1) at 55°C. Oligonucleotides modified by one to five THIQ groups in various positions were obtained. The zwitter-ionic character of the obtained derivatives was reflected in their varying mobility under conditions of denaturing PAGE. The thermal stability of the duplexes of oligodeoxynucleotides containing THIQ groups with complementary DNA and RNA only slightly differed from that of natural DNA:DNA and DNA:RNA duplexes. The results reported suggest that oligonucleotides modified with zwitter-ionic THIQ groups as antisense therapeutic agents.