Synthesis and biological activity of substance P analogs containing pyrohomoglutamic acid and homoglutamine.

Eight substance P analogs substituted by L- or D-pyrohomoglutamic acid (6-oxo-2-piperidinecarboxylic acid) and L or D-homoglutamine at the position 5 and 6 were prepared by the solid phase method. The contractile activities of the analogs were compared with that of SP on isolated guinea-pig organs.