Abstract: The subject invention involves processes for making 1-aminohydantoin compounds using a solid support resin, comprising the following steps; (a) preparing a resin-bound protected &agr;-hydrazinyl ester; (1) by reacting the resin with an &agr;-bromo carboxylic acid, then with a protected hydrazine; or (2) by reacting the resin with a protected &agr;-hydrazinyl carboxylic acid; (b) preparing a resin-bound imine by removing the blocking group from the hydrazinyl moiety, then reacting the unprotected hydrazinyl moiety with an aldehyde or ketone; (c) preparing a resin-bound secondary urea: (1) by reacting the imine with p-nitrophenylchloroformate or trisphosgene, then with a primary amine; or (2) by reacting the imine with an isocyanate, and (d) preparing the 1-aminohydantoin compound by removing the secondary urea from the resin and cyclizing it.