This invention provides compounds which are useful as inhibitors of protein tyrosine phosphatases (PTPases). As inhibitors of PTPases the compounds of the invention are useful for the management, treatment, control and adjunct treatment of diseases in mammals mediated by PTPase activity. Such diseases include type I diabetes, type II diabetes, immune dysfunction, AIDS, autoimmunity, glucose intolerance, obesity, cancer, psoriasis, allergic diseases, infectious diseases, inflammatory diseases, diseases involving the modulated synthesis of growth hormone or the modulated synthesis of growth factors or cytokines which affect the production of growth hormone, or Alzheimer's disease.