114797-69-2Relevant academic research and scientific papers
Catenated Cyclodextrins
Armspach, Dominique,Ashton, Peter R.,Ballardini, Roberto,Balzani, Vincenzo,Godi, Anna,et al.
, p. 33 - 55 (2007/10/02)
A novel synthetic approach is described for the construction of catenanes in aqueous solution from a partially methylated cyclodextrin (CD)-namely, heptakis(2,6-di-O-methyl-β-cyclodextrin) (DM-β-CD)- and a range of substrate molecules that contain a hydrophobic central core in the form of a 4,4'-disubstituted biphenyl unit (usually bitolyl) carrying two hydrophilic polyether side chains terminated by primary amine functions.In water, the amphiphilic catenane precursors form 1:1 complexes with β-CD and DM-β-CD and 2:1 (guest:host) complexes with the larger γ-CD.Macrocyclizations of the biphenyl-containing substrates with aromatic diacid chlorides in aqueous solution and in the presence of DM-β-CD under Schotten-Baumann conditions afforded - in low yields - a range of - and catenanes.When a consitutionally asymmetrical diamine was employed as the substrate, orientational isomers of a catenane were obtained.A catenane incorporating a macrocyclic tetralactam was found to exist as a mixture of head-to-head and head-to-tail isomers, which could be separated by high pressure liquid chromatography and identified unambiguously by nuclear magnetic resonance spectroscopy.One of the catenanes afforded good single crystals from which the solid state structure was determined by X-ray crystallography.Other techniques which aided the characterization of these novel compounds included ultraviolet/visible and luminescence spectroscopy, dynamic nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry.Generally speaking, the catenated cyclodextrins are soluble in halogenated and aromatic hydrocarbons as well as in hydroxylic solvents.The existence of these new compounds gives us a unique insight into the nature of the noncovalent bonding interactions that cyclodextrins employ in binding substrate molecules. - Keywords: catenanes * cyclodextrins * macrocycles * orientational isomerism
Structural Mapping of an Unsymmetrical Chemically Modified Cyclodextrin by High-field Nuclear Magnetic Resonance Spectroscopy
Spencer, Catriona M.,Stoddart, J. Fraser,Zarzycki, Ryszard
, p. 1323 - 1336 (2007/10/02)
Samples of 2,6-per-O-methyl-β-cyclodextrin (DMβCD), prepared according to literature procedures, have shown to be less then 70percent pure.The major impurity has been identified as the unsymmetrical over-methylated cyclodextrin derivative (DM + 1)βCD.Samples of pure DMβCD and (DM + 1)βCD have been prepared by (i) benzoylating a chromatographically homogeneous mxture obtained after methylating βCD with dimethyl sulphate, (ii) separating chromatographically the resulting DMβCD heptabenzoate (DMβCD-B7) and (DM + 1)βCD hexabenzoate 6>, and then (iii) subjecting the pure perbenzoates to de-O-benzoylation.Both DMβCD-B7 and (DM + 1)βCD-B6 have been fully characterised.High-resolution 1H and 13C n.m.r. spectroscopy, COSY, J-resolved, JMOD, XHCORRD, and CHORTLE) for signal assignment and n.O.e. difference spectroscopy for residue sequencing, has been used to assign individually (i) 41 out of the 49 heterotropic protons and (ii) 29 out of the 42 heterotropic carbon atoms of the unsymmetrical (DM + 1)βCD-B6 (nuclei associated with O-methyl and O-benzoyl groups were excluded from consideration).The complete spectroscopic characterisation of unsymmetrical chemically modified cyclodextrins is important in the investigation of these compounds as potential enzyme models.The necessity of preparing pure chemically modified cyclodextrin derivatives cannot be over-emphasised.
