A synthetic protocol is described which allows the incorporation of the γ-amide (Kan) and the γ-benzyl ester [Kai(Bzl)] and ether [Kol(Bzl)] of kainicacid (Kai) into peptide chains as exemplified with the synthesis of the substance P (SP) analogs [Kan5]-SP5−11, [Glp5. Kan6]-SP5−11. [Kan6]-SP6 11.[Glp5. Kai(Bzl)11]-SP5−11 and [Glp5. Kol(Bzl)11]-SP5−11.