Chirality Gearing in an Achiral Cage through Adaptive Binding

• Published in: Journal of the American Chemical Society Vol. 144; no. 14; pp. 6180 - 6184
• Main Authors: Hu, Qi-Ping, Zhou, Hao, Huang, Teng-Yu, Ao, Yu-Fei, Wang, De-Xian, Wang, Qi-Qiang
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 13.04.2022; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Molecular Conformation; Physical Sciences; Science & Technology; Stereoisomerism; CIRCULAR-DICHROISM; RESOLUTION
• DOI: 10.1021/jacs.2c02040
• ISSN: 0002-7863

Herein we report an adaptive, achiral trithiourea molecular cage and its conformational and stereodynamics toward tricarboxylate anion binding. The cage was readily synthesized in four steps with a 44% yield for the irreversible cage-forming reaction. It possesses a flexible conformation and strongly binds 1,3,5-benzene tricarboxylate by forming a sandwich-like inclusion complex, with an affinity up to 106 M–1 in acetonitrile. Upon binding, the cage is locked in a twisted helical conformation. By incorporation of three chiral arms on the guest, a gear-like complex dominant in one given helical sense was produced. Due to the steric crowding in the helical grooves, a small change of methyl to ethyl on guest caused a striking difference on binding and chiral induction. The system thus represents a rare example of chiral induction on a flexible, achiral host and provides a decoupled model that the generation of a racemate and following chiral discrimination can be individually probed.