Synthesis and Characterization of Pseudopeptide Bradykinin B2 Receptor Antagonists Containing the 1,3,8-Triazaspiro[4.5]decan-4-one Ring System

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Abstract
A series of pseudopeptides containing alkyl-, cycloalkyl-, aryl-, and aralkyl-substituted 1,3,8-triazaspiro[4.5]decan-4-one-3-acetic acids as amino acid surrogates to replace the Pro2-Pro3-Gly4-Phe5 section of the peptide bradykinin B2 receptor antagonist [Pro3, Phe5]HOE 140 (D-Arg0-Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-D-Tic7+ ++-Oic8-Arg9) were prepared. These psuedopeptides were examined in vitro for their B2 receptor affinities as well as for their ability to block bradykinin mediated actions in vivo. Two compounds in particular, NPC 18521 (I) and NPC 18688 (V) were quite potent in these latter assays, indicating that a significant portion of this prototypical second generation decapeptide antagonist can be replaced with a more compact nonpeptide molecule.