The synthesis of optically active 5‐phenylhydantoins

Abstract

Abstract A number of reagents have been examined for effecting the conversion of an optically pure 2‐phenylhydantoic acid to an optically active 5‐phenylhydantoin. Trifluoroacetic anhydride (TFAA method) and dilute hydrochloric acid (acid‐catalysis method) proved to be the reagents of choice. The dependence of the kinetics of racemization of the 5‐phenylhydantoin system on temperature has been studied in dilute hydrochloric acid solution to support the conclusion that 5‐phenylhydantoins prepared by the acid‐catalysis method are nearly, if not entirely, optically uniform.