Patent ID: 7728167

Claim:
A process for the preparation of an enantiomerically enriched N-protected amino acid from a mixture of both enantiomers, comprising crystallizing the salt of one enantiomer of the N-protected amino acids with an enantiomerically pure N-unprotected β-amino acid derivative to form a diastereomeric salt pair consisting of one enantiomer of said N-protected amino acid and said enantiomerically pure N-unprotected β-amino acid derivative, and wherein the desired N-protected amino acid is recovered from said diastereomeric salt pair, wherein N-protected amino acid is selected from benzyloxycarbonylphenylalanine, benzyloxycarbonylvaline, benzyloxycarbonylamino-butyric acid, benzyloxycarbonylamino-tert.leucine, and wherein N-unprotected β-amino acid is selected from (R)-3-amino-3-phenylpropionic acid ethyl ester and (S)-3-amino-3-phenylpropionic acid ethyl ester.