Synthesis and anti-virus activity of some nucleosides analogues

New 3 '-, 5 '-, 5-bromo-2 '-deoxyuridine (3a-g) and 3 '-, 5 '- thymidine (4 a-i) analogues with amino acid and peptide residues were synthesized and ev aluated for antiviral activity. The influence of long peptide chains, essen tial amino acids and the effect of this structural modification on the anti viral activity has been also reported. Three 5-bromo-2 '-deoxyuridine derivatives containing glycyl-, glycyl-glycy l- and glycyl-glycyl-glycyl- residues (3a, 3b, 3c) showed a strong activity against the herpes virus PsRV and a moderate one vs. HSV-1. The corresponding thymidine analogues were considerably less effective, and only compounds 4d and 4h showed a borderline effect against PsRV.