There is provided a labeling precursor compound represented by the following general formula (2):wherein R1 represents an alkynyl group, an alkynyloxy group, an azide group, an azidoalkyl group, an arylazide group, a monocyclic or condensed polycyclic aryl group or a nitrogen-containing heterocycle R2 and R3 each independently represent an alkyl group or a hydroxyalkyl group which hydroxy group may be protected with a protecting group, and n is an integer of 1 or 2 R6 represents an alkyl group or —CONR11R12 wherein R11 and R12 each independently represent an alkyl group or a monocyclic or condensed polycyclic aryl group and R4, R5, R7 and R8 each independently represent a hydrogen atom, an alkyl group or an alkoxy group.
