| abstract |
The method of enantiomeric enrichment of D- and L-threo-2-amino-3-hydroxy-3-phenylpropionic acids of the general formula I wherein R.sup.1 is. and R.sup.2.n. is always one of the species m, water, hydroxy, halogen, nitro, trifluoromethyl, alkyl of 1 and 6 carbon atoms, alkoxy of 1 and 6 carbon atoms, alkylsulfonyl of 1 and 6 carbon atoms, alkylsulfinyl with 1 and 6 carbon atoms, or alkylthio with 1 and 6 carbon atoms, R 3, 3, 3, 3, 3, 3, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6 or 6. is water k or methyl; is a carboxylic acid group and a salt thereof, if R is a hydrogen atom, the mixture is brought into contact with D-threonine aldole in aqueous solution; which is enzymatically active with respect to the D-threo-enantiomer but essentially inactive with respect to the L-threo-enantiomer, and to convert a substantial amount of the D-threo-enantiomer into the corresponding benzaldehyde derivatives and the amino acid derivatives of the formula R CH (NH.sub.2.n.) COOR.sup.4.n, where the L-threo-enantiomer of st. |