Lledó, Agustí

FUNCTIONAL CAVITANDS

Cavitands are synthetic molecules with a permanent concave shape that can accommodate smaller molecules or ions inside. The encapsulation of a molecule in the confined space of cavitands has dramatic consequences for the reactivity of the bound species, and these effects can be harnessed to develop enzyme-like reactivity and catalysis. A prerequisite for this is the functionalization of the inner space with reactive groups that are in close contact with the bound substrate, very much like catalytic residues in the active site of an enzyme.
Our lab has developed a variety of functional receptors based on the amide-stabilized cavitand scaffold. We have developed urea and thiourea functionalized receptors towards the development of bioinspired carbocationic cylization reactions. Additionally, we have proven the versatility of this system by attaching it to highly reactive iron and manganese complexes used in C–H oxidation reactions. This system provides a robust and promising platform for bioinspired site-selective oxidation reactions.

NEW SYNTHETIC RECEPTORS

A limitation of conventional cavitands is their narrow binding space. In addition, these receptors have a strong preference for rigid pseudo-cylindrical conformation, which poses a limitation to accessing adaptable confined spaces. A distinct feature of proteinogenic receptors is their conformational flexibility, which allows them to adapt to guests of different sizes and shapes through induced fit or conformational selection phenomena. This is an essential trait for some biological functions (e.g. enzymatic catalysis) that is very difficult to introduce by design in artificial systems.
Within this conceptual framework, a second research direction in our lab aims at developing new synthetic platforms that would be more amenable to generalizing enzyme-like catalysis. Our efforts focus on hydrogen bond stabilized calix[5]arene derived cavitands. We have developed a receptor that is structured, yet flexible enough to adapt to an incoming guest of complementary size, such as coronene, a large polycyclic aromatic hydrocarbon. Current efforts are directed towards using these expanded and flexible confined spaces to promote new bioinspired reactivity.