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Several heterocyclic analogues of the potent 1-[4-(aminoalkoxy)phenylsulfonyl]indolizines were synthesized and evaluated for their antagonistic calcium activities in comparison with the 1-sulfonylindolizine SR 33557 and the usual calcium antagonist references verapamil, cis-(+)-diltiazem, and nifedipine. The bicyclic nine-membered rings were, in general, more potent than the bicyclic 10-membered or five-membered rings. Among the bicyclic nine-membered rings, the indole nucleus appeared to be extremely favorable to support the calcium antagonistic activity. In particular, compound 36, with an IC50 value for the inhibition of 3Hnitrendipine equal to 0.072 nM, is among the most potent calcium antagonist known. This compound has been selected for clinical development.
Gubin et al. (Sat,) studied this question.