| abstract |
Method for the preparation of p-hydroxyphenylglycine enriched with the D- enantiomer (D-HPG), using an asymmetric transformation of a (racemic) mixture of the enantiomers of p-hydroxyphenylglycine (HPG) with the aid of D-bromocamphorsulphonic acid (D-BrCas) in the presence of a racemization agent, where a solid diastereomeric salt of D-HPG and D-BrCas is formed, and the asymmetric transformation is carried out in an aqueous medium and in the presence of inorganic salts. In a specially preferred embodiment, HPG is first prepared from glyoxylic acid, phenol and an amino group donor, and the resulting reaction mixture, which contains HPG and the inorganic salts, is then used in the asymmetric transformation as such. D-HPG is preferably added to the reaction mixture obtained in the asymmetric transformation. |