Synthesis and Calcium channel antagonist activity of Nifedipine analogues with Chloroindolyl substituent

Various diester analogues of nifedipine in which the ortho nitrophenyl group at position 4 were replaced by 3-chloro-1H-2-indolyl substituent, were synthesized and evaluated as calcium antagonists on guinea-pig ileal smooth muscle. Nifedipine was used as a standard. Compound 6f was found to be the most active.