title: Chemical clockwise tridifferentiation of alpha- and beta-cyclodextrins: bascule-bridge or deoxy-sugars strategies.
abstract: The selective and efficient functionalisation of large concave molecules is a chemical challenge opening the door to various applications, such as artificial enzymes. We propose here a method, based on deprotection of benzylated cyclodextrins, to selectively access a variety of complex structures with two or three new different functionalities on the primary platform. Our strategy is based on a mechanistic hypothesis involving the approach of an aluminium reagent between the primary oxygen atom and the endocyclic one of the same sugar unit. Due to its cyclic directionality, a change in steric hindrance on a given position of the cyclodextrin has a different effect on the clockwise or the counterclockwise directions. This concept is illustrated and exploited in two complementary ways: deoxygenation of the primary position of two diametrically opposed sugars induces a debenzylation reaction on the neighbouring clockwise sugars of alpha- and beta-cyclodextrins. Reversible capping, or bascule-bridging, of the same pair of sugars has the same effect on the debenzylation of alpha-cyclodextrin, but induces an important change of the geometry of beta-cyclodextrin, hence allowing the selective access to yet another functionalisation pattern. A combined use of deoxygenation and bascule-bridging allows the access to an alpha-cyclodextrin with its three pairs of primary functions differentiated and ready for further modifications. Bascule-bridge or deoxy-sugars are two complementary means to operate steric decompression and induce selective reactions to efficiently access a number of new patterns of functionalities on concave molecules.
authors.affiliation: Universite Pierre et Marie Curie (Paris 6), Institut de Chimie Moleculaire (FR 2769), Laboratoire de Chimie Organique (UMR CNRS 7611), 4 place Jussieu, Paris, France.
authors.forename: Olivia
authors.initials: O
authors.lastname: Bistri
authors.forename: Pierre
authors.initials: P
authors.lastname: Sinaÿ
authors.forename: Jesùs
authors.initials: J
authors.lastname: Jiménez Barbero
authors.forename: Matthieu
authors.initials: M
authors.lastname: Sollogoub
mesh_terms: D001554:Benzene / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry*; D003837:Deoxy Sugars / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry; D013237:Stereoisomerism; D047391:alpha-Cyclodextrins / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D003837:Deoxy Sugars; D047391:alpha-Cyclodextrins; D047392:beta-Cyclodextrins; D006859:Hydrogen; D001554:Benzene; D010100:Oxygen