Structure of the calcium channel antagonist, nimodipine

Isopropyl 2-methoxyethyl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydro-3,5- pyridinedicarboxylate, C21H26N2O7, Mr = 418.45, orthorhombic, P2(1)2(1)2(1), a = 12.5897 (6), b = 14.6410 (9), c = 11.636 (1) A, V = 2144.8 (2) A3, Z = 4, Dm = 1.29, Dx = 1.30 g cm-3, lambda(Cu K alpha) = 1.54178 A, mu = 7.77 cm-1, F(000) = 888, T = 298 K, R = 0.047 for 1629 observed reflections. The structure of the title compound is similar to that of related analogs, the nitrophenyl ring being roughly normal to the dihydropyridine ring, which is in a boat conformation (N1 is 10.75 degrees out of the C2-C3-C5-C6 plane; C4 is 19.55 degrees out of plane). The 3,5 substituents are in an extended conformation, away from the 2,6 methyl groups. The nitro group is distal to N1. Structure/activity relationships of 1,4-dihydropyridines are discussed in light of this structure.