Methods for producing and separating erythro- and threo-2-hydroxy-3-nitrobutanoic acid compounds

Preparation of threo-2-hydroxy-3-nitrobutanoic acid derivatives or a mixture of erythro- and threo-2-hydroxy-3-nitrobutanoic acid derivatives having an erythro:threo ratio of 1:1 comprising reacting a 2-hydroxy-3-nitrobutanoic acid derivative (I) with not less than one equivalent of a base to cause isomerization, is new. Preparation of threo-2-hydroxy-3-nitrobutanoic acid derivatives or a mixture of erythro- and threo-2-hydroxy-3-nitrobutanoic acid derivatives having an erythro:threo ratio of 1:1 comprises reacting a 2-hydroxy-3-nitrobutanoic acid derivative of formula (I) with not less than 1 equivalent of a base (B1) or not less than 1.5 equivalents of a base (B2) other than potassium carbonate in a solvent to isomerize the erythro isomer to the threo isomer or vice versa. [Image] R : optionally substituted alkyl or aryl. ACTIVITY : None given. MECHANISM OF ACTION : None given.