The introduction of chiral alkyl substituents into the lower rim of calix[4]arene immobilised in the 1,3-alternate conformation led to a system possessing a preorganised ureido cavity hemmed with chiral alkyl units in the near proximity. As shown by the ¹H NMR titration experiments, these compounds can be used as receptors for chiral anions in DMSO-d₆. The chiral recognition ability can be further strengthened by the introduction of another chiral moiety directly onto the urea N atoms. The systems with double chiral units being located around the binding ureido cavity showed better stereodiscrimination, with the highest selectivity factor being 3.33 (K_L/K_D) achieved for N-acetyl-ʟ-phenylalaninate. The structures of some receptors were confirmed by single crystal X-ray analysis.

中文翻译：

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使用基于杯[4]芳烃的脲基受体以1,3-交替构型进行手性阴离子识别

将手性烷基取代基引入固定在1,3-交替构象的杯[4]芳烃的下边缘中，导致系统具有一个预先组织的脲基腔，该腔在近处具有手性烷基单元。如¹ H NMR滴定实验所示，这些化合物可用作DMSO- d _6中手性阴离子的受体。通过将另一个手性部分直接引入到尿素N原子上，可以进一步增强手性识别能力。具有双手性单元的系统位于结合尿素腔周围，表现出更好的立体分辨，最高选择性因子为3.33（K _L / K _D）获得了N-乙酰基-ʟ-苯丙氨酸盐。通过单晶X射线分析确认了某些受体的结构。