摘要 |
There are described compounds of the formula <CHEM> where X is hydrogen, halogen, loweralkyl, loweralkoxy or trifluoromethyl; R is - @-R4 or -@@-R4, R4 being loweralkyl; R1 is hydrogen, loweralkyl or arylloweralkyl; R2 is hydrogen, loweralkyl or arylloweralkyl; and R3 is loweralkyl, with the proviso that when R is acetyl, R3 is methyl and X is hydrogen, R1 and R2 are not both hydrogen, or pharmaceutically acceptable acid addition salts thereof, which are useful for enhancing memory and for treating Alzheimer's disease. |