| abstract |
The present invention provides modified oligonucleotides, wherein, amongst the first four bases on the 5'-end, they have the base sequence AT or TA and, bound to one of the two O- groups of the 5'-phosphate group of the first nucleotide at the 5'-end of said oligonucleotide, they contain a radical of the general formula: <IMAGE> (I) in which R4 is a spacer group and R1, R2 and R3 are hydrogen atoms or alkyl or alkoxy radicals containing up to 3 carbon atoms. These modified oligonucleotides can be used for blocking the replication and/or expression of genes which have a sequence complementary with the modified oligonucleotides. |