Evaluation of short-tether Bis-THA AChE inhibitors. A further test of the dual binding site hypothesis Original Research Article

To provide a further test of the dual binding site hypothesis proposed for acetylcholinesterase (AChE) inhibitor heptylene-linked bis-(9-amino-1,2,3,4-tetrahydroacridine) A7A, short-tether (ethylene–hexylene) homologs A2A–A6A were prepared. En route to these compounds, convenient and scaleable syntheses of useful pharmaceutical intermediate 9-chloro-1,2,3,4-tetrahydroacridine 3 and A7A were developed. AChE and butyrylcholinesterase (BChE) inhibition assays of A2A–A10A confirm that a seven methylene tether (A7A) optimizes AChE inhibition potency and AChE/BChE selectivity. Finally, these studies indicate that simultaneous binding of alkylene-linked 9-amino-1,2,3,4-tetrahydroacridine dimers to the catalytic and peripheral sites of AChE is possible with a tether length as short as 5 methylenes. ©