Compounds of formula I: including any possible stereoisomers thereof, wherein: R1 is hydrogen, —C(═O)R6 or —C(═O)CHR7—NH2; R2 is hydrogen; or C1-C6alkyl or phenyl, either of which is optionally substituted with 1, 2 or 3 substituents each independently selected from halo, C1-C6alkyl, C2-C6-alkenyl and C1-C6alkoxy, hydroxy or amino, or R2 is naphtyl; or R2 is indolyl, R3 is hydrogen, C1-C6alkyl, benzyl; R4 is hydrogen, C1-C6alkyl, benzyl; or R3 and R4 together with the carbon atom to which they are attached form C3-C7cycloalkyl; R5 is C1-C10alkyl, C3-C7-cycloalkyl, benzyl, or phenyl, any of which being optionally substituted with 1, 2 or 3 substituents each independently selected from hydroxy, C1-C6alkoxy, amino, mono- and diC1-C6alkylamino; R6 is C1-C6 alkyl; R7 is C1-C6 alkyl; R8 is hydrogen or halogen; or a pharmaceutically acceptable salt or solvate thereof are useful in the prophylaxis or treatment of HCV infections.