Abstract: Compounds of formula (I), and salts and prodrugs thereof ##STR1## wherein Q.sup.1 is halo substituted phenyl; naphthyl; indolyl; benzthiophenyl; benzofuranyl; benzyl; or fluorenyl;. . is an optional covalent bond;one of X and Y is H and the other is hydroxy or C.sub.1-6 alkoxy, or X and Y are together .dbd.O or .dbd.NOR.sup.5 ;R.sup.1 and R.sup.2 are H; C.sub.1-6 alkyl optionally substituted by hydroxy, cyano, COR.sup.c, CO.sub.2 R.sup.c, CONR.sup.c R.sup.d, or NR.sup.c R.sup.d (where R.sup.c and R.sup.d are H, C.sub.1-6 alkyl or phenyl(C.sub.0-4 alkyl) optionally substituted by C.sub.1-6 alkyl, C.sub.1-6 alkoxy, halo and trifluoromethyl); phenyl(C.sub.1-4 alkyl) (optionally substituted by C.sub.1-6 alkyl, C.sub.1-6 alkoxy, halo or trifluoromethyl); COR.sup.c ; CO.sub.2 R.sup.c ; CONR.sup.c R.sup.d ; COC.sub.1-6 alkylNR.sup.c R.sup.d ; CONR.sup.c COOR.sup.d ; or SO.sub.2 R.sup.c ;R.sup.3 is H, C.sub.1-6 alkyl or C.sub.2-6 alkenyl; andR.sup.4 is phenyl optionally substituted by C.sub.1-6 alkyl, C.sub.