PROBLEM TO BE SOLVED: To provide a production method of a radioactively labeled exendin derivative.SOLUTION: In a production method of polypeptide, a molecular probe precursor of the formula (1) is labeled using a labeled compound capable of labeling lysine or a lysine derivative. Y-Leu-Ser-Xaa-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Xaa-Asn-Gly-Y(1), where Yrepresents an amino acid sequence with 1 to 8 amino acids deleted from the N-terminal side of (2), Xaarepresents lysine or a lysine derivative, Xaarepresents a basic amino acid with the side chain having no functional group to which the labeled compound reacts, and Yrepresents an amino acid sequence with the 1 to 9 amino acids deleted from the C terminal side. His-Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp (2) Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser (3)【課題】放射性標識されたｅｘｅｎｄｉｎ誘導体の製造方法の提供。【解決手段】式(１)の分子プローブ前駆体を、リジン又はリジン誘導体を標識可能な標識化合物を用いて標識するポリペプチドの製造方法。Y1-Leu-Ser-Xaa12-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Xaa27-Asn-Gly-Y2(１)、Y1は(２)のＮ末端側から１～８個のアミノ酸が欠失したアミノ酸配列を示し、Xaa12はリジン又はリジン誘導体を示し、Xaa27は側鎖に前記標識化合物が反応する官能基を有さない塩基性アミノ酸を示し、Y2はＣ末端側から１～９個のアミノ酸が欠失したアミノ酸配列を示す。His-Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp(２)Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser(３)【選択図】図５
