The invention concerns compounds of formula (I), wherein R1 represents a hydrogen, halogen atom, an alkyl, polyhalogenoalkyl, cyano, nitro, hydroxycarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, or dialkylaminocarbonyl group; R2 represents a hydrogen atom, an alkyl, aryl group optionally substituted, heteroaryl optionally substituted or a R20-C(X) group, R20 representing an alkyl, alkoxy, amino, alkylamino, dialkylamino, aryl optionally substituted or heteroaryl group; X represents an oxygen atom, a sulphur atom, or a NR21 group, wherein R21 represents a hydrogen atom or an alkyl group; R3 represents a hydrogen atom or an alkyl group; n represents an integer between 1 and 6 inclusively, R1 has the following meanings (A); their enantiomers, diastereoisomers, as well as their addition salt to a pharmaceutically acceptable acid or base. The invention is useful for preparing medicines.