The present invention concerns the compounds having the formula N-oxides, salts, stereoisomeric forms, racemic mixtures, prodrugs, esters and metabolites thereof, wherein R1 and R8 each are H, optionally substituted C1-6alkyl, C2-6alkenyl, C3-7cycloalkyl, aryl, Het1, Het2; R1 may also be a radical of formula (R11aR11b)NC(R10aR10b)CR9—; t is 0, 1 or 2; R2 is H or C1-6alkyl; L is —C(═O)—, —O—C(═O)—, —NR8—C(═O)—, —O—C1-6alkanediyl-C(═O)—, —NR8—C1-6alkanediyl-C(═O)—, —S(═O)2—, —O—S(═O)2—, —NR8—S(═O)2; R3 is C1-6alkyl, aryl, C3-7cycloalkyl, C3-7cycloalkylC1-4alkyl, or arylC1-4alkyl; R4 is H, C1-4alkylOC(═O), carboxyl, aminoC(═O), mono- or di(C1-4alkyl)aminoC(═O), C3-7cycloalkyl, C2-6alkenyl, C2-6alkynyl or optionally substituted C1-6alkyl; R5 and R6 are H or C1-6alkyl. It further relates to their use as broadspectrum HIV protease inhibitors, processes for their preparation as well as pharmaceutical compositions and diagnostic kits comprising them. It also concerns combinations thereof with another anti-retroviral agent, and to their use in assays as reference compounds or as reagents.