Novel compounds of the general formula (I), ##STR00001## wherein Ar, R.sub.1, R.sub.2, X.sub.1, X.sub.2, Y.sub.1, Y, and Z are as defined in the specification, the use of these compounds as pharmaceutical compositions, pharmaceutical compositions comprising the compounds and methods of treatment employing these compounds and compositions. The present compounds may be useful in the treatment and/or prevention of conditions mediated by Peroxisome Proliferator-Activated Receptors (PPAR), in particular the PPAR.delta. subtype.