Bicyclic dihydropyrimidines 3 imitating the in vitro potency of dihydropyridine calcium channel blockers (e.g., nifedipine 2) are described. Structure-activity studies show a pyrazole ring can effectively mimic the combined effect of N3substituent (R3) and CZhetero atom (X) of monocyclic dihydropyrimidines 1. These results support our previous hypothesis about the requirement of a vinylogous urethane for calcium channel blocking activity and a nonspecific role for the N3-substituent and C2-hetero atom (X) of 1.