alkylacetoacetate with methyl‐, ethyl‐ or isopropyl3‐aminocrotonate and 1‐methyl‐5‐nitroimidazole‐2‐carboxaldehyde. Calciumchannelantagonistactivities were determined in vitro using a guinea pig ileum longitudinal smooth muscle (GPILSM)assay. Many compounds exhibited superior, or equipotent, calciumantagonistactivity (IC50 = 10—10 to 10—13 M range) relative to the reference drug nifedipine (IC50