wherein L 1 , L 2 , L 3 , Q 1 , Q 2 , R 1 , R 2 , X, Y and Z are as decribed in the description fo the invention, provide pharmacological agents which are inhibitors of PTPases, in particular, the compounds of formula I inhibit PTP-1B and TC PTP, and thus may be employed for the treatment of conditions associated with PTPase activity. Accordingly, the compounds of formula I may be employed for prevention or treatment of insulin resistance associated with obesity, glucose intolerance, diabetes mellitus, hypertension and ischemic diseases of the large and small blood vessels. In addition, the compounds of the present invention may be employed to treat or prevent cancer, osteoporosis, neurodegenerative and infectious diseases, and diseases involving inflammation and the immune system.