Method for manufacturing peptide compound, reagent for forming protecting group, and hydrazine derivative

A method for producing a peptide compound comprising a step in which a hydrazine derivative represented by formula (1) is used, a reagent for forming a protecting group including said compound, and a hydrazine derivative. In formula (1), a ring A represents an aromatic hydrocarbon ring or an aromatic hetero ring, R represents a hydrogen atom, an amino protecting group, an amino acid residue, or a peptide residue, k represents an integer of 1 to 5, n represents 1 or 2, and each RA independently represents an aliphatic hydrocarbon group or an organic group having an aliphatic hydrocarbon group.