Synthesis, calcium-channel blocking activity, and conformational analysis of some novel 1,4-dihydropyridines: application of PM3 and DFT computational methods

Novel 1,4-dihydropyridines were synthesized and subjected to calcium-channel blocking evaluation and conformational analysis using semi-empirical (PM3) and density functional theory (DFT) as computational methods. All molecules had a boat-like 1,4-dihydropyridine ring in both the methods. In PM3 method almost 54% of the molecules were deviated from planarity, but in DFT method all the molecules had perfect flattened-boat conformation. Using both the methods, the C-4 substituent was pseudoaxial with its phenylamino substitution in sp orientation in 82.14% of the molecules. Trans–trans and cis–cis conformation had the greatest and lowest proportion in the molecules, respectively. Trans–trans conformers which possessed sp conformation for the substituted group on the imidazole ring were active calcium-channel blocking agents.