Benzazepinone calcium channel blockers. 3. Synthesis and structure-activity studies of 3-alkylbenzazepinones

As part of a program aimed at identifying novel analogues of diltiazem, we developed several synthetic routes for 3-alkylbenzazepinones, both in racemic and nonracemic form. Structure-activity relationship studies in this series have led to identification of several analogues as potent calcium channel blocking agents, both in vitro and in vivo. Analogues containing a 6-trifluoromethyl substituent (17a and 17b) are the most potent vasorelaxants in vitro. The oral antihypertensive activity of these compounds is comparable to its 3-acetoxy derivative 1 (X = 6-CF3) and 8-chlorodiltiazem (2b). The 3-allyl analogue 17c is a more potent antihypertensive agent than 17a, 17b, or 8-chlorodiltiazem (2b), and has a longer duration of action in vivo.