Improved Acylation Rates within Cyclodextrin Complexes from Flexible Capping of the Cyclodextrin and from Adjustment of the Substrate Geometry

Article abstract of DOI:10.1021/ja00522a054

The acylation of β-cyclodextrin by bound substrates has been studied as a model for serine acylase enzymes such as chymotrypsin.Molecular model building suggested that previously examined substrates, which had given acylation rates only a few hundred times accelerated over the hydrolysis rates, were not optimal geometrically.In our work the geometry for such processes has been improved by fashioning an "intrusive floor" on the cyclodextrin cavity, leading to improved rates.Greater improvements have come from substrate modification, using substrates based on the cinnamic acid, adamantane, and ferrocene frameworks.The rates correlate well with the geometric predictions from molecular models.The best case leads to an acceleration of acylation, relative to hydrolysis, of 10⁶-10⁷-fold, exceeding that for chymotrypsin with p-nitrophenyl acetate.