HETEROBAMBUSURILS: UNIQUE SYNTHETIC ANION BINDERS

Bambusurils represent a relatively new family of host molecules that have a unique structure and intriguing binding properties. Being different from cucurbiturils, in which the guest molecules interact with the hydrophobic concave face of the glycoluril building block, the guest in bambusurils interacts with the convex face of glycoluril unit, offering diametrically different binding interactions with anions and other electron-rich species.^[1]

Our studies with monomeric thio-glycolurils^[2] led us to explore the synthesis of semithio-bambusurils and study their anion binding properties in comparison with the all-oxygen analogs.^[3] In order to gain broader insight into the entire landscape of heteroatom substitution in these molecules we first calculated the binding properties of monomeric glycoluril analogs, as well as their corresponding bambusurils.^[4] The most significant conclusion from these studies was the prediction that semiaza-bambus[6]uril would possess an open tunnel with positive electrostatic potential along the main axis of the molecule, which could simultaneously accommodate multiple anions. Motivated by these predictions we embarked on a synthetic effort to achieve these molecules. Here we report that semiaza-bambusurils are easily accessible from the corresponding semithio-bambusurils in a one-pot, scalable reaction. We show that this transformation converts a single anion host into a multiple anion binder that may function as a unique anion channel.^[5]

References:

1. Yawer, M. A.; Havel, V.; Sindelar, V. Angew. Chem. Int. Ed. 2015, 54, 276 –279.
2. Singh, M.; Parvari, G.; Botoshansky, M.; Keinan, E.; Reany, O. Eur. J. Org. Chem. 2014, 933–940.
3. Singh, M.; Solel, E.; Keinan, E.; Reany, O. Chem. Eur. J. 2015, 21, 536 – 540.
4. Solel, E.; Singh, M.; Reany, O.; Keinan, E. submitted.
5. Singh, M.; Solel, E.; Keinan, E.; Reany, O. submitted.