Compounds represented by the following structural formula (I), and pharmaceutically acceptable salts, solvates and hydrates thereof, wherein R1 is an unsubstituted or substituted aryl, heteroaryl, cycloalkyl, aryl-alkyl, heteroaryl-alkyl or cycloalkyl-alkyl, R2 is H, alkyl or haloalkyl, the polymethylene chain (II), is saturated or may contain a carbon-carbon double bond, while n is 2, 3, 4, W is O or S, Y is an unsubsituted or substituted phenylene, naphthylene or 1, 2, 3, 4 tetrahydronaphthylene, R3 is H, alkyl or haloalkyl. R4 is H, alkyl, haloalkyl or a substituted or unsubstituted benzyl, are useful for modulating a peroxisome proliferator activated receptor, particularly in the treatment of diabetes mellitus.