title: Complexes of peracetylated cyclodextrin in a non-aqueous aprotic medium: the role of residual water.
abstract: This paper describes the interaction between aromatic esters and peracetylated cyclodextrins (CDs) studied by NMR spectroscopy in deuterochloroform (CDCl3). The observed chemical shift changes highlight the existence of interactions between an aromatic alkyl ester, water and peracetylated CDs. In some cases, substituent chemical shift determination was influenced by the low water content of CDCl3 and/or the host molecule. Higher CD concentrations resulted in water signal drifts in all studied cases. It was not possible to obtain a completely dry sample of peracetyl γCD: ∼1 mol of water remained and the water signal showed reversed movement, with respect to the other two CD analogues, upon increasing host concentration. The estimated 1 : 1 stability constants for the water : peracetyl CD complexes are in the 50-150 M(-1) range in CDCl3, but show a relatively large calculation error. The calculated 1 : 1 stability constants for the peracetyl CD : ester complexes are also in this range, but 1 : 2 and 2 : 1 complex compositions are also possible. Overall, our results highlight dynamic aspects of water nanoconfined in a highly hydrophobic environment, thus mimicking biological recognition where a few water molecules often play a pivotal role.
authors.affiliation: Dipartimento di Scienza e Tecnologia del Farmaco, University of Turin, Via P. Giuria, 9, 10125, Turin, Italy. ljicsinszky@gmail.com giancarlo.cravotto@unito.it.
authors.forename: Laszlo
authors.initials: L
authors.lastname: Jicsinszky
authors.forename: Katia
authors.initials: K
authors.lastname: Martina
authors.forename: Marina
authors.initials: M
authors.lastname: Caporaso
authors.forename: Pedro
authors.initials: P
authors.lastname: Cintas
authors.forename: Andrea
authors.initials: A
authors.lastname: Zanichelli
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Cravotto
mesh_terms: D002725:Chloroform / Q000737:chemistry*; D003505:Cyclodextrins / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry*; D015394:Molecular Structure; D066244:Proton Magnetic Resonance Spectroscopy; D014867:Water / Q000737:chemistry*
chemical_list: D003505:Cyclodextrins; D014867:Water; D002725:Chloroform; D003903:Deuterium