Compounds of formula (I) and pharmaceutically acceptable salts, solvates and hydrolysable esters thereof wherein X is O or S X1 is O or S; X is S or O; R1 and R2 are independently H, methyl, or halogen; R4 and R5 are independently H or C1-3 alkyl or R4 and R5 may, together with the carbon atom to which they are bonded, form a 3 5 membered cycloalkyl ring; R6 and R7 are independently H, C1-3 alkyl, or allyl; each R3 is independently halogen, C1-6 straight or branched alkyl, or CF3; and y is 0, 1, 2, 3, 4 or 5 act as hPPAR alpha agonists.