title: Thiourea-linked upper rim calix[4]arene neoglycoconjugates: synthesis, conformations and binding properties.
abstract: The thiourea group has been exploited to link two or four carbohydrate units at the upper rim of tetrapropoxycalix[4]arene derivatives in the cone conformation. Two synthetic methodologies were used, the first one consisting of the condensation of di- and tetraminocalix[4]arenes with the isothiocyanate of monosaccharides in dry CH2Cl2 at room temperature and the second one exploiting the condensation of an aminolactoside with a calixarene isothiocyanate. The first method allows the glycoconjugates to be obtained in 75-80% overall yields. The disfunctionalized derivatives exist in a closed flattened cone conformation in CDCl3 and CD3OD due to the formation of intramolecular hydrogen bonds involving the thiourea groups which are broken in DMSO-d6 to give an open flattened cone conformation. The thiourea groups act not only as linkers but also as binding units for anionic substrates as evidenced by solution 1H NMR and ESI-MS experiments. Turbidimetric analysis indicates that the tetraglucoside and tetragalactoside clusters give specific interactions with Concanavalin A (Con A) and peanut lectin (PNA), respectively. Both features show that the neoglycoconjugates could also be used as site specific molecular delivery systems.
authors.affiliation: Dipartimento di Chimica Organica e Industriale, Università degli Studi, Parco Area delle Scienze 17/A, I-43100 Parma, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sansone
authors.forename: Elisa
authors.initials: E
authors.lastname: Chierici
authors.forename: Alessandro
authors.initials: A
authors.lastname: Casnati
authors.forename: Rocco
authors.initials: R
authors.lastname: Ungaro
mesh_terms: D047250:Calixarenes; D003208:Concanavalin A / Q000378:metabolism; D006001:Glycoconjugates / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D009391:Nephelometry and Turbidimetry; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000378:metabolism; D019887:Peanut Agglutinin / Q000378:metabolism; D010636:Phenols / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D013890:Thiourea / Q000737:chemistry*
chemical_list: D006001:Glycoconjugates; D009943:Organophosphorus Compounds; D019887:Peanut Agglutinin; D010636:Phenols; C121325:calix(4)arene; D003208:Concanavalin A; D047250:Calixarenes; D013890:Thiourea