Compounds of general formula (I), stereoisomers and pharmaceutically acceptable salts thereof, wherein each of Z and Z' are independently H or F; Q is (a), CH(OH), (b); X is H, Br, Cl, F or CF3; Y is H, Br, Cl, F, OH, OR5, OC(O)R4, N3, CN, NO2, SO3H, CO2R4, NH2, NHR9, NR9R'9, C(R6)(R7)(V'R8) or C(O)R7, provided that when both Z and Z' are F, then Y is H or F; V and V' are each independently CH2 or O; R1 is H or CH3; R2, R9 and R'9 are each independently (C1-6)alkyl, or R2 and V-R3 taken together with the carbon atom to which they are attached form a 3-6 membered ring; R3, R6, R7 and R8 are each independently H, (C1-6)alkyl, or (C3-6)cycloalkyl; R4 is H, (C1-10)alkyl, (C0-4)alkylene aryl or (C3-8)cycloalkyl; and R5 is (C1-10)alkyl, benzyl, phenethyl or (C3-6)cycloalkyl, possess anticholinesterase activity and may be used in the treatment of Degenerativa Dementias.