Compound of formula (I): wherein: n represents 0 or 1, R1 represents hydrogen, arylalkyl, alkyl, acyl, alkoxycarbonyl, arylalkoxycarbonyl or trifluoroacetyl, R2 represents alkyl, X represents oxygen, chlorine, OR3, SR4 or NOR5, R3 represents hydrogen, alkyl, acyl, alkoxycarbonyl or arylalkoxycarbonyl, R4 represents hydrogen, alkyl or aryl, R5 represents hydrogen or optionally substituted alkyl, represents a single or double bond, Ar represents aryl or heteroaryl, its isomers and addition salts thereof with a pharmaceutically acceptable acid, and medicinal products containing the same which are useful as facilitators of memory and cognition and antalgic agents.