The coordination mode to lithium, magnesium, calcium and zinc cations of racemic vs. enantiopure amino acids and racetam APIs is analysed and its effect on chiral selection critically reviewed. It is shown that chiral resolution in the solid state can be obtained via cocrystallization of racemic compounds with an achiral inorganic salt coformer, such as LiX (X=Cl, Br, I) or ZnCl₂, which favour tetrahedral coordination in the solid state. The chiral selection may take the form of conglomerate crystal formation or of selective homochiral aggregation in racemic crystals. When cocrystallization involves alkaline earth metal cations, such as Ca²⁺ and Mg²⁺, which favour octahedral coordination, heterochiral complexation is observed in most cases, with formation of racemic crystals.

中文翻译：

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通过与无机盐共结晶的手性拆分

分析了外消旋与对映纯氨基酸和外消旋 API 的锂、镁、钙和锌阳离子的配位模式，并严格审查了其对手性选择的影响。结果表明，固态手性拆分可以通过外消旋化合物与非手性无机盐共形成物（例如 LiX (X=Cl, Br, I) 或 ZnCl ₂）的共结晶获得，它们有利于固态中的四面体配位。手性选择可以采取聚集晶体形成或外消旋晶体中选择性同手性聚集的形式。当共结晶涉及碱土金属阳离子时，例如 Ca ²⁺和 Mg ²⁺，有利于八面体配位，在大多数情况下观察到异手性络合，形成外消旋晶体。