It is intended to provide a labeling precursor compound used for selectively producing radioactive halogen-substituted syn-1-amino-3-cyclobutane-carboxylic acids, and to provide a process for producing a radioactive halogen-substituted syn-1-amino-3-cyclobutane-carboxylic acid using the labeling precursor compound. A labeling precursor is used in which a phthalimide group is used as a protective group for protecting the amino group. The syn-form of the radioactive halogen-substituted 1-amino-3-cyclobutanecarboxylic acid can be selectively produced by labeling the labeling precursor with a radioactive halogen followed by deprotecting.提供放射性鹵素取代之順式-1-氨基-3-鹵代環丁烷羧酸、選擇性製造之標示前驅物化合物以及使用該化合物之放射性鹵素取代順式-1-氨基-3-鹵代環丁烷羧酸之製造方法。氨基之保護基係使用酞醯亞胺作為標示前驅物,將此標示前驅物以放射性鹵素標示,藉由進行脫保護,能夠選擇性地製造順式體之以放射性鹵素取代之1-氨基-3-鹵代環丁烷羧酸。
