Crystal structures of calcium channel antagonists: 2, 6-dimethyl-3, 5-dicarbomethoxy-4-[2-nitro-, 3-cyano-, 4-(dimethylamino)-, and 2, 3, 4, 5, 6-pentafluorophenyl]-1, 4-dihydropyridine

The crystal structures of 2, 6-dimethyl-3, 5-dicarbomethoxy-4-(2-nitrophenyl).l, 4-dihydropyridine (Nifedipine) and the 3-cyano-, 4-(dimethylamino)- and 2, 3, 4, 5, 6-pentafluorophenyl derivatives were determined. The 1, 4-dihydropyridine ring in all four compounds has a boat-type conformation with varying degrees of puckering at the C4 position. Increasing distortion from planarity at this position shows a limited correlation with decreasing biological activity, determined as the ability to inhibit the Ca²⁺-dependent muscarinic-induced mechanical responses of guinea pig ileal longitudinal smooth muscle.