A compound represented by the following chemical formula; a tautomer or stereoisomer of the compound; or a salt of the compound, the tautomer, or the stereoisomer: where in the chemical formula, R 1 and R 2 are each a Group 1 element or a protecting group of an amino group and may be identical to or different from each other, or alternatively, R 1 and R 2 together may form a protecting group of an amino group, R 3 is a protecting group of a hydroxy group, R 4 is PR 5 R 6 R 7 R 8, wherein R 5, R 6, R 7, and R 8 are each a Group 1 element, a lone electron pair, a Group 16 element, a Group 17 element, a protecting group of a phosphorus atom or an amino group, and may be identical to or different from each other, J is a hydrogen atom or an arbitrary atomic group, A is a hydrogen atom, a hydroxy group, an alkyl group, an aralkyl group, an alkoxy group, an electron-withdrawing group, a silylene group, or a sulfide group, or alternatively, J and A together may form a linker, L is a single bond or a linker (a linking atom or a linking atomic group), the main chain length (the number of main chain atoms) of the linker is arbitrary, L may or may not contain each of C, N, O, S, P, and Si in the main chain, and may or may not contain each of a single bond, a double bond, a triple bond, an amide bond, an ester bond, a disulfide bond, an imino group, an ether bond, a thioether bond, and a thioester bond in the main chain, Z is an atomic group that can form a peptide bond with a labeling compound and does not contain a label, and the atomic group that can form a peptide bond with the labeling compound is an atomic group comprising an ester group or a carbonyl group or is a carboxylic halide group (halocarbonyl group). R 1 and R 2 are each a Group 1 element or a protecting group of an amino group and may be identical to or different from each other, or alternatively, R 1 and R 2 together may form a protecting group of an amino group, R 3 is a protecting group of a hydroxy group, R 4 is PR 5 R 6 R 7 R 8, wherein R 5, R 6, R 7, and R 8 are each a Group 1 element, a lone electron pair, a Group 16 element, a Group 17 element, a protecting group of a phosphorus atom or an amino group, and may be identical to or different from each other, J is a hydrogen atom or an arbitrary atomic group, A is a hydrogen atom, a hydroxy group, an alkyl group, an aralkyl group, an alkoxy group, an electron-withdrawing group, a silylene group, or a sulfide group, or alternatively, J and A together may form a linker, L is a single bond or a linker (a linking atom or a linking atomic group), the main chain length (the number of main chain atoms) of the linker is arbitrary, L may or may not contain each of C, N, O, S, P, and Si in the main chain, and may or may not contain each of a single bond, a double bond, a triple bond, an amide bond, an ester bond, a disulfide bond, an imino group, an ether bond, a thioether bond, and a thioester bond in the main chain, Z is an atomic group that can form a peptide bond with a labeling compound and does not contain a label, and the atomic group that can form a peptide bond with the labeling compound is an atomic group comprising an ester group or a carbonyl group or is a carboxylic halide group (halocarbonyl group).