Abstract: Compounds of formula (I), and salts and prodrugs thereof ##STR1## wherein n is 1, 2 or 3;X represents O or S;Y represents a hydrocarbon chain of 1, 2, 3 or 4 carbon atoms optionally substituted by oxo;R.sup.1 is phenyl optionally substituted by 1, 2 or 3 of C.sub.1-6 alkyl, C.sub.2-6 alkenyl, C.sub.2-6 alkynyl, halo, cyano, nitro, trifluoromethyl, trimethylsilyl, --OR.sup.a, SR.sup.a, SOR.sup.a, SO.sub.2 R.sup.a, --NR.sup.a R.sup.b, --NR.sup.a COR.sup.b, --NR.sup.a CO.sub.2 R.sup.b, --CO.sub.2 R.sup.a or --CONR.sup.a R.sup.b ;R.sup.2 is phenyl, indazolyl, thienyl, furyl, pyridyl, thiazolyl, tetrazolyl, quinolyl, benzhydryl, or benzyl;R.sup.4 and R.sup.5 each independently represent H, halo, C.sub.1-6 alkyl, oxo, CH.sub.2 OR.sup.a, CO.sub.2 R.sup.a or CONR.sup.a R.sup.b ;R.sup.8 represents an optionally substituted aromatic heterocycle; andR.sup.a and R.sup.b are H, trifluoromethyl, C.sub.1-6 alkyl or phenyl optionally substituted by C.sub.