Resolution of Amino Acids. VIII. The Preparation of the Four Optical Isomers of β-Hydroxyaspartic Acid

The ammonolysis of cis-epoxy succinic acid yielded threo-hydroxy-Dl-aspartic acid exclusively, but that of trans-epoxy acid produced a mixture of 68% erythro- and 32% threo-hydroxyaspartic acid. This mixture was separated into the two pure diastereomers through either a Dowex 1 column chromatography or fractional crystallization after the mixture had been changed to ammonium salt. The threo- and erythro-Dl-amino acids so prepared were resolved by optically active lysine and ornithine respectively. The contribution (partial molar rotation) of the α-and β-asymmetric centers to the observed molar rotations of the optically active diastereomeric hydroxyaspartic acids in water and 5 n hydrochloric acid was calculated.