Abstract: The present invention is directed to compounds represented by the following structural formula, and pharmaceutically acceptable salts, solvates and hydrates thereof, R1 is a substituted or unsubstituted group selected from C1-C8 alkyl, aryl-C0-2-alkyl, heteroaryl-C0-2-alkyl, C3-C6 cycloalkylaryl-C0-2-alkyl or phenyl. W is O or S. R2 is H or a substituted or unsubstituted group selected from C1-C6 alkyl, C3-C6 cycloalkyl and heteroaryl. X is a C2-C5 alkylene linker wherein one carbon atom of the linker may be replaced with O, NH or S. Y is C, O, S, NH or a single bond. Furthermore, E is (CH2)nCOOH, wherein n is 0, 1, 2 or 3, or C(R3)(R4)A, wherein A is an acidic functional group such as carboxyl, carboxamide substituted or unsubstituted sulfonamide, or substituted or unsubstituted tetrazole. R3 is H, saturated or unsaturated C1-C5 alkyl, C1-C5 alkoxy.