STUDIES RELATED TO THE SYNTHESIS OF CHLORAMPHENICOL.Ⅵ RACEMIZATION AND REDUCTION OF L-α-DICHLORACETYLAMINO-β-HYDROXY-p-NITROPROPIOPHNON

L-α-Dichloracetylamino-β-hydroxy-p-nitropropiephenone could be prepared in much better yield than its corresponding acetylamino-compound. In contrast to the statement made by Kollonitsch et al., we found that this compound underwent racemization at room temperature steadily in ethanol or isopropanol containing pyridine when the less soluble racemic compound crystallized out in good yield (nearly theoretical when the mother liquor was recycled). It was observed that, in a solution of acetic acid, racemization occurred only in the presence of sodium acetate. This gave further support to the theory that racemization was the result of a process of prototropic rearrangement. Meerwein-Ponndorf reduction of DL-α-dichloracetylamino-β-hydroxy-p-nitropropiophenone, when modified by the addition of a small amount of sodium isopropylate, gave yields of DL-chloramphenicol up to 53 to 55% of theory.