Conformational features of calcium channel agonist and antagonist analogs of nifedipine.

The crystal and molecular structures of methyl 2,6-dimethyl-5-nitro-4-(2-trifluoromethylphenyl)-1,4- dihydropyridine-3-carboxylate and ethyl 4-(2-difluoromethoxyphenyl)-1,4,5,7,-tetrahydro-2-methyl-5-oxof uro[3,4-b]pyridine-3-carboxylate, which are analogs of the calcium channel antagonist nifedipine reported to have agonist activity, have been determined. The conformations of these two agonists are compared with the conformational features shown by nifedipine and related 1,4-dihydropyridine calcium channel antagonists. Common conformational features shown by these agonists and antagonists allow both to bind to the same plasma membrane receptor while subtle differences in hydrogen-bonding activity of the amine group, and ester group orientation and hydrophobic fit, may control the availability of channel open and closed states.