The present invention is directed to compounds represented by the following structural formula, Formula I: and stereoisomers, pharmaceutically acceptable salts, solvates and hydrates thereof, wherein: (a) X is selected from the group consisting of O, S, S(O)2, N, and a bond; (b) U is an aliphatic linker wherein one carbon atom of the aliphatic linker may be replaced with O, NH or S, and wherein such aliphatic linker is optionally substituted with R30; (c) Y is selected from the group consisting of C, O, S, NH and a single bond; and (d) E is C(R3)(R4)A or A.