45228-AC4
The Inverted Cucurbit[n]uril Family
The Isaacs laboratory has been actively engaged in studying the properties of a new class of compounds known as cucurbit[n]urils (CB[n]). These CB[n] compounds function as molecular containers for their target compounds in water. Real-world containers which are used to protect, ship, and otherwise modify the properties of the materials held within. Molecular containers behave similarly and are used in a wide variety of real world applications like the formulation of hydrophobic drugs, chemical sensors, and even as the active ingredient in the household product Febreeze(tm). Cyclodextrins are currently the most commonly used molecular container despite several drawbacks including weak binding, fast release and challenges to chemical functionalization. With support from ACS-PRF the Isaacs group is studying the properties of CB[n] compounds and more specifically inverted CB[n] compounds which have properties (e.g. tight binding, controlled release, potential for functionalization) that surpass those of the cyclodextrins. One of the main issue that has been confronting the CB[n] field is that the mechanism of CB[n] formation has been obscure which makes it difficult to rationally modify the synthesis procedure to selective target a new type of molecular container. With PRF support we have studied the mechanism of the conversion of i-CB[6] to CB[6]. Remarkably, i-CB[6] undergoes an intramolecular isomerization that leads to CB[6] in high yield. This process proceeds via a very interesting moboid-CB[6] as an intermediate. These studies also provided clues toward the mechanism of CB[n] formation that lead us to formulate the process as a step growth polymerization under kinetic control that proceeds toward thermodynamically controlled formation of CB[5]-CB[7] as stable products. The insights gained from these studies allowed us to prepare new CB[n] type receptors (e.g. double cavity host and chiral CB[n]) in a tailor-made fashion.
