A compound of formula (I) in which the dotted lines indicate the presence of at least one double bond; n=0 to 4; R3 and R4 are H, or when n=1, R3 and R4 can also form together a double bond between the carbon atoms, and m=0, 1 or 2, Z is CH or N or Z is C and —CHR3— is ═CH— linked by the double bond to cyclopentanone; or −(−)m- is absent, and Z is NH, >N-alkyl, >N-phenyl, >N-benzyl or >N heteroaryl; R8 is alkyl, aryl or heteroaryl which can be optionally substituted; EWG represents an electron withdrawing group selected from the group comprising COOR, COSR, CONRR′, CN, COR, CF3, SOR, SO2R, SONRR′, SO2NRR′, NO2, halogen, heteroaryl; and the pharmaceutical salts and stereisomers thereof. The compounds of formula (I) are potent in the treatment of neurodegenerative diseases such as Alzheimer's disease.