title: Synthesis, structure, and inclusion capabilities of trehalose-based cyclodextrin analogues (cyclotrehalans).
abstract: Concise and efficient strategies toward the synthesis of D2h- and D3h-symmetric cyclodextrin analogues alternating alpha,alpha'-trehalose disaccharide subunits and pseudoamide segments (cyclotrehalans, CTs) are reported. The conformational properties of these cyclooligosaccharides are governed by the rigidity of the alpha,alpha'-trehalose disaccharide repeating unit and the partial double-bond character of the N-(C=X) linkages. In contrast to the typical concave-shaped cavity of cyclodextrins (CDs), CTs feature a convex-shaped hydrophobic cavity in which the beta-face of the monosaccharide subunits is oriented toward the inner side, as supported by NMR and modeling (molecular mechanics and dynamics) studies. In the case of cyclodimeric CTs (CT2s), the existence of intramolecular hydrogen bonds results in collapsed cavities, too small to allow the formation of inclusion complexes with organic molecules. Cyclotrimeric CTs (CT3s) display cavity sizes that are intermediate between those of alphaCD and betaCD, ideally suited for the complexation of complementary guests with ternary symmetry such as adamantane 1-carboxylate (AC). The higher flexibility of the pseudoamide bridges as compared with classical glycosidic linkages endow these glyconanocavities with some conformational adaptability properties, making them better suited than CDs for complexation of angular guests, as seen from comparative inclusion capability experiments against the fluorescent probes 6-p-toluidinonaphthalene-2-sulfonate (TNS; linear) and 8-anilinonaphthalene-1-sulfonate (ANS; angular).
authors.affiliation: Departamento de Química OrgAnica, Facultad de Química, Universidad de Sevilla, Apartado 1203, E-41012 Sevilla, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Rodríguez-Lucena
authors.forename: Juan M
authors.initials: JM
authors.lastname: Benito
authors.forename: Eleuterio
authors.initials: E
authors.lastname: Alvarez
authors.forename: Carlos
authors.initials: C
authors.lastname: Jaime
authors.forename: Javier
authors.initials: J
authors.lastname: Perez-Miron
authors.forename: Carmen Ortiz
authors.initials: CO
authors.lastname: Mellet
authors.forename: José M García
authors.initials: JM
authors.lastname: Fernandez
mesh_terms: D002234:Carbodiimides / Q000737:chemistry; D003505:Cyclodextrins / Q000138:chemical synthesis* / Q000737:chemistry; D019791:Guanidine / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D014199:Trehalose / Q000737:chemistry*
chemical_list: D002234:Carbodiimides; D003505:Cyclodextrins; D014199:Trehalose; D019791:Guanidine