Abstract
The crystal and molecular structure of nilvadipine, 5-isopropyl-3-methyl-2-cyano-6-methyl-4-(3-nitrophenyl)-1, 4-dihydro-3, 5-pyridinedicarboxylate, was elucidated by X-ray structural analysis. The dihydropyridine ring adopted a boat-type conformation with the phenyl ring attached to the pseudo-axial position. Each carbonyl double bond in the ester side chains was conjugated with a neighboring double bond of the dihydropyridine ring to form a plane involving the ester group. Nonbonding interaction between the two rings was reduced by puckering of the dihydropyridine ring, lengthening of the exocyclic bond at the pseudo-axial position and twisting of the phenyl ring, keeping the meta-nitro group away from the bulky isopropyl ester group. The nuclear Overhauser effects observed in chloroform solution suggest free rotation of the phenyl ring at the pseudo-axial position about the exocyclic bond.
