The invention relates to compounds of the formula I: 1 wherein one of R.sup.5, R.sup.6 and R.sup.7 is 2 and X.sup.1, X.sup.2, R.sup.1 to R.sup.15 and n are as defined in the description, and pharmaceutically acceptable salts and/or esters thereof. The invention further relates to pharmaceutical compositions containing such compounds, to a process for their preparation and to their use for the treatment and/or prevention of diseases which are modulated by PPAR .delta. and/or PPAR.alpha. agonists.