Synthesis of Cryptophane-223-Type Derivatives with Dual Functionalization.

In this article, we present the synthesis of new cryptophane-type hosts capable of binding xenon in aqueous media and that may be useful for the development of xenon-based magnetic resonance imaging derivatives. The synthetic route proposed was chosen to facilitate both the introduction of water-solubilizing substituents and the functionalization of the host with a single arm showing recognition properties that constitute two crucial steps. This was made possible by preparing new cryptophane-223 derivatives bearing two different chemical functions that can be easily modified at a later stage. Thus, subsequent reactions allowed the design of a new cryptophane host able to bind zinc or nickel cations. The ability of this molecule to bind cationic species was assessed by calorimetric titration experiments and hyperpolarized ¹²⁹ Xe NMR. The advantages and disadvantages of this approach are discussed.