Abstract: A compound selected from those of formula (I): wherein: R1 represents hydrogen, aryl(C1-C6)alkyl, linear or branched (C1-C6)alkyl, linear or branched (C1-C6)acyl, linear or branched (C1-C6)alkoxycarbonyl, aryl(C1-C6)alkoxycarbonyl, or trifluoroacetyl, R2 represents hydrogen, linear or branched (C1-C6)alkyl, X represents oxygen or NOR3, R3 represents hydrogen, linear or branched (C1-C6)alkyl optionally substituted by one or more identical or different groups selected from hydroxy, amino and linear or branched (C1-C6)alkoxy, Ar represents aryl or heteroaryl, its isomers, and addition salts thereof with a pharmaceutically acceptable acid or base, and medicinal products containing the same which are useful in the treatment of cognitive disorders and which possess antalgic properties.