Tuning artificial oxidase catalysis by cavity modification

Previously, the ketone-bridged α-cyclodextrin derivative 6^A,6^D-di-<i>O</i>-propan-2-on-1,3-diyl α-cyclodextrin-6^A,6^D-dicarboxylate (2) was shown to be a potent artificial oxidase. In this work, a new isomer of this compound 6^A,6^D-di-<i>O</i>-propan-2-on-1,3-diyl 3^A,3^D-diepi-α-cyclodextrin-6^A,6^D-dicarboxylate 12 was synthesized and its catalytic properties were investigated and compared to those of 2. The catalyst 12 was also an excellent artificial enzyme exhibiting <i>k</i>_cat values 0.2 to 1.1 times and <i>K</i>_m values 0.1 to 4 times higher than those of 2. The reduced cavity size and the formation of a hydrogen bond are the primary factors affecting the catalytic performance.