Chloride-Templated Macrocyclization and Anion-Binding Properties of C2-Symmetric Macrocyclic Ureas from Sucrose

A high-yielding, one-pot simultaneous synthesis and full characterization of two regioisomeric C-2-symmetrical macrocycles 3a and 3b from triphosgene and readily available hexa-O-benzyl-6,6'-diaminosucrose 1 is reported. The efficient macrocyclization (90% overall yield, similar to 1:1 ratio of 3a vs 3b) is attributed to favorable steric constraints and to a templation by a chloride anion. H-1 NMR titration studies and theoretical predictions revealed that both receptors show similar affinity for acetate and benzoate anions and enhanced preference for chloride over H2PO4-.