氯霉素之合成研究(六)L-α-二氯乙酰氨基-β-羟基-对硝基苯丙酮的混旋化和还原
STUDIES RELATED TO THE SYNTHESIS OF CHLORAMPHENICOL.Ⅵ RACEMIZATION AND REDUCTION OF L-α-DICHLORACETYLAMINO-β-HYDROXY-p-NITROPROPIOPHNON
-
摘要: 制备L-α-二氯乙酰氨基-β-羟基-对-硝基苯丙酮的收率較制备相应的乙酰氨基化合物为佳,和Kollonitsch氏等所报告的不同,我們發現这个化合物易于在含有吡啶的乙醇或異丙醇溶液中混旋化,而溶解度較小的混旋化合物即自溶液析出,收率很好(母液循环使用时,接近理論量)。观察到,在醋酸溶液中,只有在有醋酸鈉存在时才有混旋化作用发生,这点进一步支持了,混旋化通过質子轉位而进行的理論,DL-α-二氯乙酰氨基-β-羟基-对-硝基苯丙酮的Meerwein-Ponndorf氏还原,当加有少量異丙醇钠时,所得合霉素收率可达53—55%理论。Abstract: 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.
下载: