Synthesis of hydantoins from enantiomerically pure α-amino amides without epimerization

A method for the preparation of enantiomerically pure hydantoins from optically pure alpha-amino amides utilizing triphosgene is described. We also propose that the racemization observed with 1,1'-carbonyldiimidazole (CDI) for this type of reaction is due to the imidazole carbarnate intermediates.