The present invention concerns the compounds having the formula ##STR00001## N-oxides, salts, stereoisomeric forms, racemic mixtures, prodrugs, esters and metabolites thereof, wherein R.sub.1 and R.sub.8 each are H, optionally substituted C.sub.1-6alkyl, C.sub.2-6alkenyl, C.sub.3-7cycloalkyl, aryl, Het.sup.1, Het.sup.2; R.sup.1 may also be a radical of formula (R.sub.11aR.sub.11b)NC(R.sub.10aR.sub.10b)CR.sub.9--; t is 0, 1 or 2; R.sub.2 is H or C.sub.1-6alkyl; L is --C(.dbd.O)--, --O--C(.dbd.O)--, --NR.sub.8--C(.dbd.O)--, --O--C.sub.1-6alkanediyl-C(.dbd.O)--, --NR.sub.8--C.sub.1-6alkanediyl-C(.dbd.O)--, --S(.dbd.O).sub.2--, --O--S(.dbd.O).sub.2--, --NR.sub.8--S(.dbd.O).sub.2; R.sub.3 is C.sub.1-6alkyl, aryl, C.sub.3-7cycloalkyl, C.sub.3-7cycloalkylC.sub.1-4alkyl, or arylC.sub.1-4alkyl; R.sub.4 is H, C.sub.1-4alkylOC(.dbd.O), carboxyl, aminoC(.dbd.O), mono- or di(C.sub.1-4alkyl)aminoC(.dbd.O), C.sub.3-7cycloalkyl, C.sub.2-6alkenyl, C.sub.2-6alkynyl or optionally substituted C.sub.1-6alkyl; ##STR00002## R.sub.5a and R.sub.5b is C.sub.2-6alkenyl, C.sub.2-6alkynyl, C.sub.3-7cycloalkyl or C.sub.1-6alkyl, optionally substituted on one or more atoms; R.sub.5a and R.sub.5b may also be hydrogen, aryl, Het.sup.1, Het.sup.2; R.sub.6 is hydrogen or C.sub.1-6alkyl optionally substituted on one ore more carbon atoms. 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.