An X-ray crystal structural analysis revealed that (2S,3S)-N-acetyl-2-amino-3-methylpentanoic acid (N-acetyl-l-isoleucine; Ac-l-Ile) and (2R,3S)-N-acetyl-2-amino-3-methylpentanoic acid (N-acetyl-d-alloisoleucine; Ac-d-aIle) formed a molecular compound containing one Ac-l-Ile molecule and one Ac-d-aIle molecule as an unsymmetrical unit. This molecular compound is packed with strong hydrogen bonds forming homogeneous chains consisting of Ac-l-Ile molecules or Ac-d-aIle molecules and weak hydrogen bonds connecting these homogeneous chains in a fashion similar to that observed for Ac-l-Ile and Ac-d-aIle. Recrystallization of an approximately 1:1 mixture of Ac-l-Ile and Ac-d-aIle from water gave an equimolar molecular compound due to its lower solubility than that of Ac-d-aIle or especially Ac-l-Ile. The results suggest that the equimolar mixture of Ac-l-Ile and Ac-d-aIle could be obtained from an Ac-l-Ile-excess mixture by recystallization from water.
X 射线晶体结构分析表明,(2S,3S)-N-乙酰基-2-
氨基-
3-甲基戊酸(N-乙酰基-l-
异亮氨酸;Ac-l-Ile)和(2R,3S)-N-乙酰基-2-
氨基-
3-甲基戊酸(N-乙酰基-d-
异亮氨酸;Ac-d-aIle)形成了一种分子化合物,其中含有一个 Ac-l-Ile 分子和一个 Ac-d-aIle 分子作为不对称单元。这种分子化合物中含有强氢键,形成由 Ac-l-Ile 分子或 Ac-d-aIle 分子组成的均质链,以及连接这些均质链的弱氢键,其连接方式类似于 Ac-l-Ile 和 Ac-d-aIle。将 Ac-l-Ile 和 Ac-d-aIle 以大约 1:1 的比例混合,从
水中重结晶得到等摩尔分子化合物,这是因为它的溶解度低于 Ac-d-aIle,尤其是 Ac-l-Ile。结果表明,可以通过从
水中重结晶的方法,从 Ac-l-Ile 过量混合物中获得 Ac-l-Ile 和 Ac-d-aIle 的等摩尔混合物。