National Research Council of Canada. NRC Institute for Biodiagnostics
National Research Council of Canada. NRC Institute for Marine Biosciences
A no. of dibenzothiazepinones and dibenzoxazepinones have been designed, synthesized and evaluated as calcium antagonists. Mol. geometries of these dibenzotricyclic calcium antagonists have been studied using x-ray crystallog., mol. modeling and two-dimensional NMR spectroscopy. X-ray diffraction reveals dibenzothiazepinoine I (X = S) and dibenzoxazepinone I (X = O) to have, resp., flexure angles of 108° and 116.9° between the two benzene rings. The mol. mechanics-optimized geometry of dibenzothiazepinone I (X = S) shows a 7° smaller flexure angle than the x-ray crystallog. result, while that of dibenzoxazepinone I (X = O) has an angle only 2° smaller than the x-ray result. AM1 and ab initio calcns. show that the side chains can affect the geometry of the tricyclic nucleus and both I (X = S, O) have neg. electrostatic potentials around the bridged portion of the tricyclics. Two-dimensional NOESY NMR spectroscopy supports the extended geometry of the 6 carbon spacer as obtained from x-ray crystallog. and mol. mechanics calcns. Vasorelaxation properties among these compds. appear to be relatively insensitive to the flexure angle and to chain length. Vasorelaxation is profoundly influenced by the nature of the basic terminal moiety.