moiety optionally substituted with n-butyl in the ortho position. [0922] In yet another embodiment of the present invention, the active compound is of formula (II), its pharmaceutically acceptable salts or prodrugs thereof, wherein: [0923] i) X is O; [0924] ii) R1 is fluorine or hydrogen; [0925] iii) R3 and R3??? are independently hydrogen or fluorine; R4 is hydrogen; and [0926] iv) R2 is a phenyl