Progress in the optimization of chiral cyclophane synthetic receptors for shape selective molecular recognition in aqueous media through hydrophobic association

Three new synthetic receptors based on Tr?ger’s base are prepared and evaluated. These three receptors are structural isomers of a successful receptor reported earlier from this laboratory, and they are all far inferior to that original receptor. Two of these receptors fail almost entirely and do so for an interesting reason. In water (not in other solvents) they collapse, forming a deflated structure. Collapsed or “sicklied” receptors do not bind to alicyclic or hydrophobic substrates in water because an important component of the driving force, the high energy waters solvating the interior of the macrocyclic structure, is lost when the receptor collapses. The results clearly illustrate how important it is to use computational methods that include good aqueous solvation models when designing new cyclophane receptors.