The invention relates to compounds of formula (I) wherein A1, R1, R2, R3, R4and R5 are defined in the descriptionand in the claims, which are preferential inhibitors of the cysteine proteasecathepsin, in particular of the cysteine protease cathepsinS or L, making them useful as medicaments, particularly in the treatment ofdiabetes, atherosclerosis, abdominal aorticaneurysm, peripheral arterial disease or diabetic nephropathy.
