Abstract: There is provided a compound of formula (I) wherein A is selected from —O— and —S—; X is selected from C2-C8 alkyl, C2-C8 alkenyl, C3-C8 cycloalkyl and C4-C8 cycloalkylalkyl, each of which may be optionally substituted with up to 3 substituents each independently selected from halo, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 alkyl-S(O)n— where n is 0, 1 or 2, —CF3, —CN and —CONH2; Y is selected from phenyl, naphthyl, dihydrobenzothienyl, benzothiazolyl, benzoisothiazolyl, quinolyl, isoquinolyl, naphthyridyl, thienopyridyl, indanyl, 1,3-benzodioxolyl, benzothienyl, indolyl and benzofuranyl, each of which may be optionally substituted with up to 4 or, where possible, 5 substituents each independently selected from halo, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 alkyl-S(O)n— where n is 0, 1 or 2, nitro, acetyl, —CF3, —SCF3 and cyano; and when Y is indolyl it may be substituted or further substituted by an N-substituent selected from C1-C4 alkyl; Z is selected from H, OR3 or F, wherein R3 is selected from H, C1-C6 alkyl and phenyl