The caged amino acid in accordance with the present invention has the structure represented by the following formula 1:
where X and Y each represent a halogen atom, an alkyl group, an alkyloxy group, an alkylamino group, or a benzo group; R1 represents a hydrogen atom or an alkyl group; R2 and R3 each represent a hydrogen atom or an alkyl group; A represents an amino acid residue; and M represents a hydrogen atom, an alkali metal, or an alkaline-earth metal.