Ishihara_1994_J.Med.Chem_37_2292

In an attempt to find central selective acetylcholinesterase (AChE) inhibitors, 3-[1-(phenylmethyl)-4-piperidinyl]-1-(2,3,4,5-tetrahydro-1H-1- benzazepin-8-yl)-1-propanones 9 and their analogs were designed on the basis of our working hypothesis of the enzyme's active site. These compounds were prepared by regioselective Friedel-Crafts acylation of 2,3,4,5-tetrahydro-1H-1-benzazepines and related nitrogen heterocycles as a key step. Most compounds showed potent inhibitory activities with IC50s in the 10-300 nM range. In order to estimate their central selectivities, we examined their effects on the apomorphine-induced circling behavior in rats with unilateral striatal lesions. Among compounds with potent AChE inhibition, 3-[1-(phenylmethyl)-4-piperidinyl]-1-(2,3,4,5-tetrahydro-1H-1- benzazepin-8-yl)-1-propanone fumarate (9a, TAK-147) (IC50 of AChE inhibition = 97.7 nM) inhibited the circling behavior at 3 mg/kg po, in which it had no significant effect on peripheral cholinergic effects. This demonstrates that 9a has favorable central selectivity. Furthermore, 9a significantly ameliorated diazepam-induced passive avoidance deficit at 1 mg/kg po. The benzazepine derivative 9a was selected as a candidate for clinical evaluation.