A series of novel S-DABO analogues (4a1-5a12) have been synthesized by an efficient method and evaluated as inhibitors of human immunodeficiency virus type-1 (HIV-1). The biological testing results clearly indicated that the substitution of halogen at the C5 position of pyrimidine ring could increase the anti-HIV-1 RT activity. The most active compounds showed activity in the low micromole range with IC(50) values (IC(50) 0.18-3.03 microM) comparable to nevirapine (IC(50) 4.12 microM). The docking showed that a new halogen bond was formed between halogen and carbonyl of TYR188 in the HIV-I RT.