Facile synthesis of a C4-symmetrical inherently chiral calix[4]arene

Inherently chiral calix[4]arenes with C-4-symmetry are extremely rare and difficult to synthesise, severely hampering any effort to expand on their potential as chiral supramolecular catalysts and building blocks. Herein we report a reaction of a tetracarbamate calix[4]arene with NBS which results in a high yield of an inherently chiral calix[4]arenes with C-4-symmetry. Furthermore, employing a chiral N-Boc proline moiety allows for separation of the diastereomers formed, thus obtaining the pure enantiomers after hydrolysis. The enantiomers could be assigned based on the CD spectra and DFT calculated values.

Automated summary

Inherently chiral calix[4]arenes with C-4-symmetry are rare and difficult to synthesise, but this study successfully obtained a high-yield product through a specific reaction. The use of a specific chiral group enabled the separation of the diastereomers formed, leading to the pure enantiomers.