Selective mTOR inhibitors of formulas (I)-(III), processes for their preparation, pharmaceutical compositions containing them, and their use in the treatment of diseases and disorders, arising from abnormal cell growth, functions, or behaviors mediated by an mTOR kinase and/or one or more PI3K enzyme, are provided. Such diseases and disorder include cancer, immune disorders, cardiovascular disease, viral infection, inflammation, metabolism/endocrine function disorders and neurological disorders.