Optical resolution by preferential crystallization and replacing crystallization of DL-allothreonine

Article abstract of DOI:10.1246/bcsj.67.1899

The ternary solubility diagranm, X-ray diffraction pattern, and infrared spectra have suggested that DL-allothreonine [DL-aThr] exists as a conglomerate. The optical resolution by successive preferential crystallization gave both D- and L-aThr of 95% optical purities in 9-13% degrees of resolution. The successive replacing crystallization was more successfully achieved by the coexisting 4-hydroxy-L-proline, as an optically active cosolute, in a racemic supersaturated solution. D-aThr of 94% optical purity was allowed to crystallize preferentially without seeding D-aThr in 24% degree of resolution, whereas L-aThr of 81% optical purity from the mother liquor was allowed to crystallize by seeding L-aThr in 22% degree of resolution. Recystallization of the obtained D- and L-aThr from water gave an optically pure form.