Patent ID: 8119813

Claim:
A method for preparing an enantiomerically enriched α-amino acid N-carboxyanhydride of formula (IIIa) or (IIIb): from the compound of formula (IIa) or (IIb) respectively: wherein in the formulae: R1 and R2 denote, independently of one another, an alkyl, alkenyl, cycloalkyl, alkylcycloalkyl, alkylaryl or aryl group; and R3 denotes an alkyl or alkylaryl group; comprising the following steps: (i) bringing the compound of formula (IIa) or (IIb) respectively into contact with SOCl 2 in a solvent; (ii) precipitating the N-carboxyanhydride formed in step (i) using a non-solvent; and (iii) recovering the N-carboxyanhydride, and not comprising any recrystallization step, nor a sublimation step of the N-carboxyanhydride.