IR, UV and NMR studies of β-cyclodextrin inclusion complexes of kazcaine and prosidol bases

The interaction of the analgesic prosidol [1-(2-ethoxyethyl)-4-phenyl-4-propionyl-oxypiperidine] and the anaesthetic kazcaine [1-(2-ethoxyethyl)-4-ethynyl-4-benzoyloxypiperidine] with β-cyclodextrin (β-CD) in aqueous solutions has been studied by nuclear magnetic resonance (NMR), ultraviolet (UV) and infrared (IR) spectroscopy. The composition and structure of the formed guest:β-CD inclusion complexes have been determined and were found to have a molar ratio of 1:2, with the guest molecule located in the cavity formed by two β-CD molecules in head-to-head orientation, with the O(2), O(3) rims interacting. The phenyl and ethoxyethyl substituents of the guests are in contact with the β-CD molecules. In contrast to prosidol–base and kazcaine–base the complexes with β-CD show a higher analgesic and local anaesthetic activity.