Diethyl 3,6-dihydro-2,4-dimethyl-2,6-methano-1,3-benzothiazocine-5,11- dicarboxylates as calcium entry antagonists: new conformationally restrained analogues of Hantzsch 1,4-dihydropyridines related to nitrendipine as probes for receptor-site conformation.

The pharmacological activity of rigid analogues of 1,4-dihydropyridine calcium entry antagonists 9-16 is demonstrated by dose-dependent inhibition of the calcium contraction in depolarized rat aortic strips and by a [3H]nitrendipine binding assay in using cardiac sarcolemmal membranes. From the results, a model is proposed as the receptor-bound conformation of the dihydropyridine calcium entry antagonists.