Abstract: Compounds of general formula I, ##STR1## wherein: A represents (CH.sub.2).sub.m optionally substituted by R.sub.3,B represents (CH.sub.2).sub.n optionally substituted by R.sub.4,R.sub.1 represents hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.1-6 alkenyl or C.sub.1-6 alkynyl,R.sub.2 represents hydrogen, C.sub.1 -C.sub.6 alkyl or COOR.sub.5, in which R.sub.5 represents C.sub.1 -C.sub.6 alkyl,R.sub.3 and R.sub.4 independently represent hydrogen or C.sub.1 -C.sub.6 alkyl,in addition, any two of R.sub.2, R.sub.3 and R.sub.4 may together form a C.sub.1-3 alkylene chain,n and m independently represent an integer from 1-3 inclusive,Y represents O or S,and pharmaceutically acceptable acid addition salts thereof are useful as pharmaceuticals, in particular as central muscarinic acetylcholine receptor agonists. The compounds are therefore useful in the treatment of diseases such as presenile and senile dementia, Huntington's chorea, tardive dyskinesia, hyperkinesia, mania and Tourette Syndrome.