The drug nifedipine (4-(2`-nitrophenyl)-l,4-dihydropyridine-3,5-dimethyl ester) (7) is a calcium channel antagonist clinically used for the treatment of hypertension and vasospastic angina. This paper presents novel dynamic NMR studies of more than twenty dihydropyridine (DHP) analogs of nifedipine that were synthesized via the Hantzsch pyridine synthesis. The NMR investigations define the barriers associated with the rotation about the dihydropyridine C4-aryl-C1 bond and the rotameric populations with respect to this position. Typically, these barriers are 50.8-53.2 kJ/mol for 4-phenyl DHP`s and 30.0-33.2 kJ/mol for 4-isoxazolyl DHP`s. The lower barriers for the isoxazolyl compounds were determined using Freon-21 as a solvent and from proton spectra collected at temperatures as low as 149 K. The replacement of the 3,5-diesters with nitriles resulted in an increase in the rotational barrier to 69.0-66.9 kJ/mol for the phenyl and ~40.4 kJ/mol for the isoxazolyl DHP`s. ¹³C NMR spectroscopy confirmed these conclusions and revealed rotational isomerism in the 3,5-diesters of the 4-phenyl DHP`s.