5'-(Bromoacetamido)-2', 5'-dideoxyuridine (3) and derivatives (8, 10, 12, and 14) substituted at the 5-position with bromo, iodo, fluoro, and ethyl groups have been synthesized as potential inhibitors of enzymes that metabolize pyrimidine nucleosides. Also prepared were 2', 5'-dideoxyuridine derivatives (4-6) substituted at the 5'-position with 2- bromopropionamido, iodoacetamido, and 4-(fluorosulfonyl) benzamido groups. ...