Abstract: A compound of formula I, ##STR1## wherein--X represents (CH.sub.2).sub.n O, (CH.sub.2).sub.n S or C.sub.2 alkylene;n represents 1 or 2;Ar.sup.1 represents indanyl, tetrahydronaphthyl, naphthyl or phenyl, which latter two groups may be substituted by one or more substituents selected from chloro, fluoro, OR.sup.1, O(CH.sub.2).sub.m CONR.sup.20 R.sup.21, C(O)R.sup.2, C.sub.1-6 alkyl (optionally substituted by one or more fluorine atoms), pyridyl, thiazinyl, phenyl or C.sub.7-9 alkylphenyl which latter two groups are optionally substituted by one or more substituent selected from halo, nitro, OR.sup.3, C.sub.1-6 alkyl (optionally substituted by one or more fluorine atoms), C(O)R.sup.4, C(O)OR.sup.5, C(O)N(R.sup.6)R.sup.7, CN, CH.sub.2 OR.sup.14, CH.sub.2 NR.sup.15 R.sup.16, N(R.sup.8)R.sup.9, N(R.sup.10)SO.sub.2 R.sup.11, N(R.sup.12)C(O)R.sup.13, OC(O)R.sup.19 and SO.sub.2 NR.sup.17 R.sup.18 ;m represents an integer 1 to 3;R.sup.1, R.sup.2 and R.sup.3 independently represent H, C.sub.