Use
Crystallise N-acetyl-L-methionine from Me2CO, H2O or EtOAc. Dry it in a vacuum over P2O5. Its solubility at 25o in H2O is 30.7%, and in Me2CO it is 29.5%. [Mitzi & Schueter Biochim Biophys Acta 27 168 1958, Birnbaum et al. J Biol Chem 194 455 1952, Beilstein 4 IV 3206.]