Synthesis and Structure−Activity Relationships of 2-Substituted <scp>d</scp>-Tryptophan-Containing Peptidic Endothelin Receptor Antagonists: Importance of the C-2 Substituent of the <scp>d</scp>-Tryptophan Residue for Endothelin A and B Receptor Subtype Selectivity
Continuing studies on modifications of potent cyclicpentapeptideendothelin (ET) receptor antagonists, represented by BQ-123, and potent linear tripeptide derivative ET receptor antagonists, represented by BQ-788, are described herein. The introduction of D-tryptophan analogues with C-2 substituents in these peptidic ET antagonists resulted in potent ET receptor antagonists with various ETA/ETB subtype selectivity