Biologically active oligodeoxyribonucleotides--I: Syntheses and anti-HIV-1 activities of 5'-modified pentadecadeoxyribonucleotides.

5'-Modified pentadecadeoxyribonucleotides with a sequence (5'-TGGGAGGTGGGTCTG-3') (15mer) complimentary (antisense) to the tat 2nd splicing acceptor region of human immunodeficiency virus type 1 (HIV-1) were prepared and evaluated for anti-HIV-1 activity. The modified antisense oligodeoxyribonucleotides (AS-ODNs) were synthesized using 5'-modified thymidine 3'-phosphoramidites as the 5'-terminal residues. The structures of the 5'-modified 15mers were confirmed by negative ion LSI mass spectroscopy, and the anti-HIV-1 activities were evaluated in vitro by the MTT assay using MT-4 cells. While the unmodified 15mer had no activity in our assay system, the 15mers bearing modifications with trityl-type substituents at the 5'-end showed high anti-HIV-1 activities.