PURPOSE: To obtain a deacylating agent useful for e.g. eliminating a protecting group from an ester by the deacylation in an organic solvent under a substantially neutral condition, exerted in drug synthetic process, by immobilizing a specific hydroxamic acid derivative to polymer beads.

CONSTITUTION: A deacylating agent comprising an N-methyl-α- dialkylacetohydroxamic acid derivative immobilized to polymer beads shown by formula I (R is insoluble polymer part; R' and R" are alkyl). A compound shown by formula II is reacted with N-methylhydroxylamine hydrochloride and then with sarcocine methyl ester to give a compound shown by formula III, which is reacted with a compound shown by formula IV to give the compound shown by formula I wherein R' and R" are CH3. The agent is useful for, e.g. deacylating an ester in releasing a photographic reagent from a precursor (ester) of the reagent by introducing almylamino group to a proper position in the molecule so that H2 can be eliminated in the molecule.