Conformationally constrained calcium channel blockers: novel mimics of 1-benzazepin-2-ones

In order to test a hypothesis that the seven-membered ring of the benzothiazepinone (diltiazem) and benzazepinone calcium channel blockers serves primarily to orient two critical pharmacophores in space, a series of novel, conformationally constrained bicyclo[2.2.2]octyl amines 3 which severely restrict the relative orientations available to the amine and methoxyphenyl groups was prepared. All compounds which positioned the pharmacophores on the same face of the molecule demonstrated vasorelaxant activity and affinity for the diltiazem receptor equal to or greater than racemic diltiazem 1 or the corresponding benzazepione 2. In addition, compound 3d was equipotent to (+)-diltiazem in its ability to reduce ischemic/reperfusion injury in an in vitro model of myocardial ischemia. However, 3d is significantly less cardiodepressive at an equivalent antiischemic dose. Therefore, the original receptor binding hypothesis led to the design and synthesis of novel calcium channel blockers with unique biological properties.