| abstract |
The present invention relates to compounds of the formula I <CHEM> where R1 is hydrogen or loweralkyl; R2 is hydrogen, loweralkyl, cycloalkyl, arylloweralkyl,loweralkylcarbonyl or loweralkoxycarbonyl; or alternatively the group <CHEM> as a whole is <CHEM> <CHEM> wherein R4 is loweralkyl and R5 is loweralkyl, cycloalkyl or arylloweralkyl; and R3 is hydrogen, <CHEM> <CHEM> wherein R6 is hydrogen, loweralkyl or phenyl, and R7 is hydrogen or loweralkyl, with the proviso that R1, R2 and R3 may not all be hydrogen, which compounds are useful for alleviating memory dysfunctions characterized by a cholinergic deficit. The invention relates further to a process for the preparation of the compounds of the invention. |