The invention relates to compounds of the formula (I) in which: i and j=1; R.sub.1 is in position 3 or 4 on the phenyl ring and represents a cyano group, an alkoxy group substituted by halogen, a thioalkyl group, an alkylcarbonyl group or an alkylsulfonyl group; and R.sub.2 represents a carboxyl group, an aikoxycarbonyl group, an alkylcarbonyl group, an unsubstituted amide group or a linear or branched alkyl group substituted by a cyano, hydroxyl, cabboxyl, aikoxycarbonyl or unsubstituted amide group; and also the pharmaceutically acceptable derivatives, salts, solvates and stereoisomers thereof, including mixtures thereof in all proportions.