The synthesis of D-erythro- and D-threo-α-amino-β,γ-dihydroxy-n-butyric acids

We repeated the synthesis of Fischer and Feldmann [2] and obtained, as they did, the amino acid with [α]D24 = -13.7° in good yield. However, in addition another α-amino-β,γ-dihydroxy-n-butyric acid, with [α]D24 = 16.0°, was isolated from the reaction mixture. It is the purpose of this communication to show that the amino acid with [α]D24 = -13.7° is not a mixture of disastereoisomers, but is D-threo-α-amino-β,γ-dihydroxy-n-butyric acid, and that the amino acid with [α]D24 = 16.0° is D-erythro-α-amino-β,γ-dihydroxy-n-butyric acid