title: Highly efficient catalysis of the Kemp elimination in the cavity of a cubic coordination cage.
abstract: The hollow cavities of coordination cages can provide an environment for enzyme-like catalytic reactions of small-molecule guests. Here, we report a new example (catalysis of the Kemp elimination reaction of benzisoxazole with hydroxide to form 2-cyanophenolate) in the cavity of a water-soluble M8L12 coordination cage, with two features of particular interest. First, the rate enhancement is among the largest observed to date: at pD 8.5, the value of kcat/kuncat is 2 × 10(5), due to the accumulation of a high concentration of partially desolvated hydroxide ions around the bound guest arising from ion-pairing with the 16+ cage. Second, the catalysis is based on two orthogonal interactions: (1) hydrophobic binding of benzisoxazole in the cavity and (2) polar binding of hydroxide ions to sites on the cage surface, both of which were established by competition experiments.
authors.affiliation: Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK.
authors.forename: William
authors.initials: W
authors.lastname: Cullen
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Misuraca
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Hunter
authors.affiliation: Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK.
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Williams
authors.affiliation: Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Ward