The compounds of the present invention are represented by the following compounds having Formula I, where the substituents R1, R4, L, M, X, Y, and s are as defined herein. The compounds of the present invention are also represented by the following compounds having Formula (Ia), Formula (Ib), or Formula (Ic), where the substituents R1-R4, RX, RY, X, Y, and s are as defined herein. These compounds are used in the treatment of cancer, immunologic disorders, autoimmune disorders, neurodegenerative disorders, or inflammatory disorders or for providing immunosuppression for transplanted organs or tissues.
