Merging Bambus[6]uril and Biotin[6]uril into an Enantiomerically Pure Monofunctionalized Hybrid Macrocycle.

Bambus[6]urils and biotin[6]urils are macrocycles with an exceptional affinity for inorganic anions. Here, we investigated statistical condensation of 2,4-dibenzylglycoluril and d-biotin, monomers of the corresponding macrocycles, to prepare the enantiomerically pure macrocycle 1 containing a single d-biotin and five glycoluril units. Host-guest properties of 1 in chloroform solution and solid state were investigated. The macrocycle 1 bearing a single functional group was employed in the formation of [1]rotaxane utilizing reversible covalent bonds.

Monofunctionalized Fluorinated Bambusurils and Their Conjugates for Anion Transport and Extraction.

Bambusurils are macrocyclic molecules that are known for their high binding affinity and selectivity toward anions. Here, we present the preparation of two bambusurils bearing fluorinated substituents and one carboxylic function. These monofunctionalized bambusurils were conjugated with crown ether and cholesterol units. The resulting conjugates were successfully tested in liquid-liquid extraction of inorganic salts and chloride/bicarbonate transport across lipid bilayers.

Bambusurils as a mechanistic tool for probing anion effects.

Bambusuril macrocycles have high affinity towards anions (X-) such as PF6- and SbF6- or BF4- and ClO4-. Therefore, addition of bambusurils to reaction mixtures containing these anions effectively removes the free anions from the reaction process. Hence, comparing reactions with and without addition of bambusurils can demonstrate whether the anions actively participate in the reaction mechanism or not. We show this approach for gold(i) mediated addition of methanol to an alkyne. The reaction mechanism can proceed via monoaurated intermediates (e.g., in catalysis with [(IPr)AuX]) or via diaurated intermediates (e.g., in catalysis with [(PPh3)AuX]). We show that anions X- slightly affect the reaction rates, however the effect stays almost the same even after their encapsulation in the cavity of bambusurils. We also demonstrate that X- affects the overall reaction rate in the very same way as the reaction rate of the protodeauration step. All results are consistent with the indirect effect of X- by the acidity of the conjugated acid HX on the rate-determining step. There is no evidence that a direct involvement of X- would affect the reaction rate.