Nuclear magnetic resonance investigations of calcium-antagonist drugs. Part 1. Conformational and dynamic features of nimodipine {3-[(2-methoxyethoxy)carbonyl]-5-(isopropoxycarbonyl)-4-(3-nitrophenyl)-2,6-dimethyl-1,4-dihydropyridine} in [2H6]dimethyl sulphoxide

Conformational and dynamic features of nimodipine in [2H6]DMSO solution were investigated by 1D and 2D n.m.r. techniques. 1H and 13C n.m.r. relaxation rates, 13C-{1H} n.O.e.s, and 2D n.O.e. proton spectra were used to build up a Dreiding model of the preferred conformation. Folding of the two side-chains in opposite directions was indicated. Complete anisotropic motion was assumed wherefrom internal reorientational times within the phenyl ring and the side-chains were evaluated. Folding of the isopropoxycarbonyl side-chain was also demonstrated by motional constraints undergone by carbon atoms within it.