Chiral selection of Tröger's base-based macrocycles with different ethylene glycol chains length in crystallization

In the present work, two Trӧger's base-based macrocycles (TBBMs) with different bridging ethylene glycol chains (T1, n = 1; T3, n = 3) were successfully synthesized and studied via the crystal analysis. These two TBBMs possess rare rectangular-like cavities and show chiral selection during the crystallization. T1 with short glycol chain (n = 1) crystallized as racemates, while T3 with long glycol chain (n = 3) was found as meso isomer. In contrast to T1 and T3, for T2 (n = 2) both rac-T2 and meso isomer R2NS2N-T2 has been observed in our previous report. Thus, the synthesis of new TBBMs T1 and T3 with different bridging ethylene glycol chains not only makes the study of TBBMs more systematically, but also helps to understand the relationship between the size of the rectangular cavity and the chiral selection of Tröger's base-based macrocycles during their crystallization.