Compounds of the formula II: wherein R2 is the side chain of leucine, isoleucine, cyclohexylglycine, O-methyl threonine, 4-fluoroleucine or 3-methoxyvaline; R3 is H, methyl or F; Rq is trifluoromethyl and Rq′ is H or Rq and Rq′ define keto; Q is a p-(C1-C6alkylsulphonyl)phenyl- or an optionally substituted 4-(C1-C6alkyl)piperazin-1-yl-thiazol-4-yl-moiety have utility in the treatment of disorders characterized by inappropriate expression or activation of cathepsin K, such as osteoporosis, osteoarthritis, rheumatoid arthritis or bone metastases.