High affinity peptide ligands for the bradykinin (BK) B2 subtype receptor have been shown to adopt a β‐turn conformation of the C‐terminal tetrapeptide (H‐Arg1‐Pro2‐Pro3‐Gly4‐Phe5‐Ser6‐Pro7‐Phe8‐Arg9‐OH). We investigated the replacement of the Pro7‐Phe8dipeptide moiety in BK or the D‐Tic7‐Oic8 subunit in HOE140 (H‐D‐Arg0‐Arg1‐Pro2‐Hyp3‐Gly4‐Thi5‐Ser6‐D‐Tic7‐Oic8‐Arg9‐OH) by 4‐amino‐1,2,4,5‐tetrahydro‐2‐benzazepin‐3‐one templates (Aba). Binding studies to the human B2 receptor showed a correlation between the affinities of the BK analogs and the propensity of the templates to adopt a β‐turn conformation. The L‐spiro‐Aba‐Gly containing HOE140 analog BK10 has the best affinity, which correlates with the known turn‐inducing property of this template. All the compounds did not modify basal inositolphosphate (IP) output in B2‐expressing CHO cells up to 10 µM concentration. The antagonist properties were confirmed by the guinea pig ileum smooth muscle contractility assay. The new amino‐benzazepinone (Aba) substituted BK analogs were found to be surmountable antagonists.
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