title: Glycoside-clustering round calixarenes toward the development of multivalent ligands. Synthesis and conformational analysis of Calix[4]arene O- and C-glycoconjugates.
abstract: Bis- and tetra-O- and C-glycosyl calixarenes (calixsugars) have been prepared by tethering carbohydrate moieties to a tetrapropoxycalix[4]arene scaffold through alkyl chains. Two methodologies have been employed. One consisted of the stereoselective multiple glycosylation of upper rim calix[4]arene polyols leading to calix-O-glycosides; the other involved a multiple Wittig olefination of upper rim calix[4]arene-derived polyaldehydes by the use of sugar phosphoranes and reduction of the alkene double bonds affording calix-C-glycosides. The NMR spectra and NOE experiments of bis-glycosylated products indicate that compounds bearing sugar-protected residues exist preferentially in solution in a flattened cone arrangement (far conformation) whereas deprotected derivatives adopt a close conformation. Calculations by molecular mechanics of the latter compounds point to a close conformation as well in gas phase.
authors.affiliation: Dipartimento di Chimica, Laboratorio di Chimica Organica, Università di Ferrara, 44100 Ferrara, Italy. adn@dns.unife.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Dondoni
authors.forename: Martin
authors.initials: M
authors.lastname: Kleban
authors.forename: Xubo
authors.initials: X
authors.lastname: Hu
authors.forename: Alberto
authors.initials: A
authors.lastname: Marra
authors.forename: Harold D
authors.initials: HD
authors.lastname: Banks
mesh_terms: D047250:Calixarenes; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods; D006027:Glycosides / Q000138:chemical synthesis* / Q000737:chemistry; D006031:Glycosylation; D007476:Ionophores / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010636:Phenols / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D006027:Glycosides; D007476:Ionophores; D008024:Ligands; D010636:Phenols; C121325:calix(4)arene; D047250:Calixarenes