Patent ID: 7253299

Claim:
A process for purifying N 2 -(1(S)-ethoxycarbonyl-3-phenylpropyl)-N 6 -trifluoroacetyl-L-lysine of the formula (1): comprising subjecting N 2 -(1(S)-ethoxycarbonyl-3-phenylpropyl)-N 6 -trifluoroacetyl-L-lysine contaminated with impurities to crystallization from a water-soluble non-protic organic solvent or a solvent containing a water-soluble non-protic organic solvent, thereby removing the impurities into the mother liquor and giving crystals of N 2 -(1(S)-ethoxycarbonyl-3-phenylpropyl)-N 6 -trifluoroacetyl-L-lysine.