syn-Cryptophanes: macrocyclic compounds with optimized characteristics for the design of ¹²⁹Xe NMR-based biosensors

A new water-soluble xenon host system with great promise for the ¹²⁹Xe NMR-based biosensing approach is presented: the syn-cryptophane-222-hexacarboxylate. It compares favorably with its already known anti diastereomer, on the one hand, and with cucurbit[6]uril, on the other hand, in particular in terms of xenon binding constant and xenon in-out exchange, a key parameter for the efficiency of the most sensitive HyperCEST method.