Patent ID: 8716439

Claim:
A method of producing a peptide by a liquid phase synthesis method, comprising steps of: Step A: reacting the active ester of the acid of a first amino acid or a first peptide with the amine of a second amino acid or a second peptide to obtain a first reaction mixture comprising an intermediate peptide, wherein the amine of the first amino acid or the first peptide has a protecting group such that the intermediate peptide has an N-terminal amine protecting group; Step B: purifying the intermediate peptide contained in the first reaction mixture obtained in Step A, wherein the purification is performed by using an amide-type solvent immiscible with water or a mixed solvent containing the amide-type solvent immiscible with water and a halogenated hydrocarbon-type solvent, and by separating the solvent layer containing the intermediate peptide from an aqueous layer; Step C: removing the N-terminal amine protecting group of the intermediate peptide obtained in Step B to form a second reaction mixture; and Step D: purifying the intermediate peptide contained in the second reaction mixture, if necessary.