Diethyl 4-(2,5-dimethoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate, conformational change with solvent of crystallization

The title compound, C21H27NO6, has been crystallized from ethanol containin g nitrobenzene and shows the phenyl ring, B, in an ap conformation. This st ructure may be compared with that of the molecule crystallized from ethanol alone, in which the B ring is seen in an sp conformation. The isolation of this rotamer has implications for the understanding of the docking of calc ium beta-blocking dihydropyridine molecules with their receptor site.