METHOD OF PREPARING DL-THREO-1-N-NITROPHENYL-2-ACETAMINO-1,3-PROPANEDIOL

In a process for the preparation of DL-threo-1-(p-nitrophenyl)-2-acetamino-1,3-propanediol from the isopropanol solution of DL-threo-1-(p-nitrophenyl)-2-acetamino-1,3-propanediol - aluminiumalcoholate compounds formed in the Meerwein-Ponndorf-Verley reduction of p-nitro- alpha -acetamino- beta -hydroxy-propiophenon via aqueous or aqueous-mineral acidic hydrolysis, evaporation and removal of the aluminium salt, the improvement that prior to or simultaneously with the separation of isopropanol the aluminium alcoholates formed in the reduction are hydrolyzed in the presence of the calculated amount or less, but not lower than 50 % of water, water vapour or of an equivalent amount of aqueous mineral acid solution, isopropanol is distilled out continuously, the powdery mixture of DL-threo-1-(p-nitrophenyl)-2-acetamino-1,3-propanediol and aluminium oxide is treated to remove aluminium in the form of its double salt and optionally the hydrolysis is completed in this leaching step, and DL-threo-1-(p-nitrophenyl)-2-acetamino-1,3-propanediol is separated.