Dynamic enzymatic synthesis of γ-cyclodextrin using a photoremovable hydrazone template

The high water solubility of γ-cyclodextrin (γ-CD) lowers its synthetic yield and complicates its post-synthetic recovery, thus increasing production costs. Here, we report the use of a photoremovable hydrazone template as a proof-of-concept strategy for increasing the efficiency of the enzymatic synthesis of γ-CD and lowering the associated production costs. Our results show that while both the Z and E isomers of the hydrazone switch form low affinity (K = 250–725 M⁻¹) complexes with β-CD (1:1), only the Z isomer of the switch can be included in γ-CD (2:1; K₂ = 8,970 M⁻¹). We used this property to preferably synthesize γ-CD and increase its yield by 6-fold and then took advantage of the photoremovable nature of the template to isolate the product. Considering the very limited number of photoswitches that can bind to γ-CDs, we anticipate that this newly discovered host-guest couple will open the way for designing γ-CD-based adaptive materials.