Synthesis and biological activities of substance P antagonists

Several substance P analogues containing various D-amino acid modifications have been synthesized by the solid-phase procedure, detached from the solid support by ammonolysis, and purified by gel filtration combined with reversed-phase chromatography. Three compounds were fair to very potent competitive antagonists of substance P on three bioassays, i.e., guinea pig ileum, rabbit mesenteric vein, and guinea pig trachea. [Arg6,D-Trp10]SP(6-11) is a reasonable antagonist in all three bioassays and [D-Pro4,D-Trp7,9]SP(4-11) is a very potent competitive antagonist with pA2 values ranging around 6.0.