A compound of Formula I or a pharmaceutically acceptable salt thereof, wherein: R 1 = R 2, R 3 and R 4 are independently hydrogen, and wherein X = hydrogen, hydroxy, nitro, halo, C 1-6 alkyl, C 1-6 alkyloxy, C 3-6 cycloalkyl, halo-substituted C 1-6 alkyl, halo-substituted C 1-6 alkyloxy, phenyl, C 2-6 alkenyl, C 3-6 cycloalkenyl or C 2-6 alkeneoxy; R d, R e, R f, R h, R k, R L, R m, R n, R o, R p independently = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, mono or dialkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, or propyl thio; R g, R i independently = hydrogen, hydroxy, halo, or C 1-5 alkyl; R j = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, alkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, propyl thio, for use in the therapeutic or prophylactic treatment of a viral infection in a mammal infected with or exposed to a virus selected from the group consisting of Lentivirus, Coronavirus, Hepatitis C virus and Equine Arteritis virus. or a pharmaceutically acceptable salt thereof, wherein: R 1 = R 2, R 3 and R 4 are independently hydrogen, and wherein X = hydrogen, hydroxy, nitro, halo, C 1-6 alkyl, C 1-6 alkyloxy, C 3-6 cycloalkyl, halo-substituted C 1-6 alkyl, halo-substituted C 1-6 alkyloxy, phenyl, C 2-6 alkenyl, C 3-6 cycloalkenyl or C 2-6 alkeneoxy; R d, R e, R f, R h, R k, R L, R m, R n, R o, R p independently = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, mono or dialkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, or propyl thio; R g, R i independently = hydrogen, hydroxy, halo, or C 1-5 alkyl; R j = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, alkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, propyl thio, for use in the therapeutic or prophylactic treatment of a viral infection in a mammal infected with or exposed to a virus selected from the group consisting of Lentivirus, Coronavirus, Hepatitis C virus and Equine Arteritis virus. R 1 = R 2, R 3 and R 4 are independently hydrogen, and wherein X = hydrogen, hydroxy, nitro, halo, C 1-6 alkyl, C 1-6 alkyloxy, C 3-6 cycloalkyl, halo-substituted C 1-6 alkyl, halo-substituted C 1-6 alkyloxy, phenyl, C 2-6 alkenyl, C 3-6 cycloalkenyl or C 2-6 alkeneoxy; R d, R e, R f, R h, R k, R L, R m, R n, R o, R p independently = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, mono or dialkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, or propyl thio; R g, R i independently = hydrogen, hydroxy, halo, or C 1-5 alkyl; R j = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, alkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, propyl thio, for use in the therapeutic or prophylactic treatment of a viral infection in a mammal infected with or exposed to a virus selected from the group consisting of Lentivirus, Coronavirus, Hepatitis C virus and Equine Arteritis virus. X = hydrogen, hydroxy, nitro, halo, C 1-6 alkyl, C 1-6 alkyloxy, C 3-6 cycloalkyl, halo-substituted C 1-6 alkyl, halo-substituted C 1-6 alkyloxy, phenyl, C 2-6 alkenyl, C 3-6 cycloalkenyl or C 2-6 alkeneoxy; R d, R e, R f, R h, R k, R L, R m, R n, R o, R p independently = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, mono or dialkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, or propyl thio; R g, R i independently = hydrogen, hydroxy, halo, or C 1-5 alkyl; R j = hydrogen, amino, halo, C 1-5 alkyl, C 1-5 alkyloxy, hydroxy, aryl, substituted aryl, substituted amino, alkyl-substituted amino, cycloalkyl-substituted amino, aryl-substituted amino, propyl thio, for use in the therapeutic or prophylactic treatment of a viral infection in a mammal infected with or exposed to a virus selected from the group consisting of Lentivirus, Coronavirus, Hepatitis C virus and Equine Arteritis virus.