Oligodeoxynucleotides containing 5-alkyl-,5(1-alkenyl)- and 5-(1-alkynyl)pyrimidines and pharmaceutical compositions containing such compounds

The invention relates to 12 to 30 nucleotide-unit long oligodeoxynucleotides containing at least one 5-substituted pyrimidine base, either uracil or cytosine, where the 5-substituent is a C3-14 n-alkyl group, a C2-8 (E)-n-1-alkenyl group, an ethynyl or a C4-12 n-1-alkynyl group. The oligodeoxynucleotides according to the invention can form double helices with complementary nucleic acids with unaltered or increased stability, possess highly increased stability against 3'-exonucleases as well as strongly increased hydrophobicity and are much better taken up by cells than the unmodified oligodeoxynucleotides. In this way, they can be efficiently used as drugs against various tumours and viruses, including HIV.