A compound of Formula I is disclosed as follows: or a pharmaceutically acceptable salt, prodrug, solvate, or metabolite thereof, wherein R is hydrogen, P(═O)(OH)2, P(═O)(O(C1-C18)alkylene(C6-C20)aryl)2, P(═O)(OH)(OM), P(═O)(OM)2, P═O(O2M), S(═O)(OH)2, S(═O)(O(C1-C18)alkylene(C6-C20)aryl)2, S(═O)(OH)(OM), S(═O)(OM)2; M is a monovalent or divalent metal ion, or alkylammonium ion; W is (C6-C20)aryl, (C6-C20)heteroaryl, (C1-C18)alkyl(C6-C20)aryl, (C1-C18)alkyl(C6-C20)heteroaryl, hydroxy(C6-C20)aryl, hydroxy(C6-C20)heteroaryl, (C1-C18)alkoxy(C6-C20)aryl, (C1-C18)alkoxy(C6-C20)heteroaryl, (C1-C18)alkylenedioxy(C6-C20)aryl, (C1-C18)alkylenedioxy(C6-C20)heteroaryl, halo(C6-C20)aryl, halo(C6-C20)heteroaryl, (C1-C18)alkylamino(C6-C20)aryl, (C1-C18)alkylamino(C6-C20)heteroaryl, (C1-C18)cycloalkylamino(C6-C20)aryl, or (C1-C18)cycloalkylamino(C6-C20)heteroaryl, and their OR8 substutes; R5 is (C1-C18alkoxy, hydrogen, hydroxyl, O—(C1-C18)alkyl(C6-C20)aryl, halo or OR8, or R5 and R6 are (C1-C18)dioxy provided that R7 is hydrogen; R6 is hydroxyl, O—(C1-C18)alkyl(C6-C20)aryl, halo or ORR, (C1-C18)alkoxy, (C1-C18)alkylamino, or (C1-C18)cycloalkylamino, or R6 and R7 are (C1-C18)dioxy provided that R5 is hydrogen; R7 is hydrogen, halo or OR8, hydroxyl, or O—(C1-C18)alkyl(C6-C20)aryl; and R8 is P(═O)(OH)2, P(═O)(O(C1-C18)alkyl(C6-C20)aryl)2, P(═O)(OH)(OM), or P(═O)(OM)2, P═O(O2M).
