the invention provides compounds of formula : which have a tacrine moiety connected to an heterocyclic moiety through a linker . through careful selection of the substituents and the linker , the activity and selectivity towards acetylcholinesterase can be modulated . the compounds show potent ache inhibition activities together with modifications in the β - amyloid aggregation properties by binding simultaneously to the catalytic and peripheral ache sites . they are useful in the treatment of ache mediated diseases , such as the alzheimer &# 39 ; s disease .