thiourea and calix(4)arene

Two-armed neutral anion receptors (4,5), were prepared and examined for their anion-binding ability using UV-vis, fluorescence and 1H NMR spectra in DMSO. The results of non-linear curve fitting indicate that 4 or 5 form 1 : 1 stoichiometric complexes with dicarboxylate anions by multiple hydrogen bonding interactions and the sensitivity for recognition of dicarboxylate depends on the chain length of these dicarboxylate anions. Receptors 4 and 5 have no binding ability with acetate, dihydrogen phosphate and the halogen (Cl-, Br-, I-) anions. This demonstrates that receptors 4 or 5 could be used as chemical sensors for some special dicarboxylate anions.

Topics: Amides; Anions; Calixarenes; Carboxylic Acids; Molecular Structure; Phenols; Thiourea

[structure: see text] We have synthesized a number of calix[4]arene derivatives presenting thiourea functional groups at their upper rims by the condensation of a 1,3-di(p-amino)calix[4]arene with alkyl isothiocyanates. Mono- and dithiourea-substituted calix[4]arenes were prepared selectively in good yields, and homocoupling of the former led to calix[4]arene dimers with a thiourea linker. X-ray crystallography revealed interesting intra- and intermolecular hydrogen bonding patterns. (1)H NMR data and computational studies also provided some insight into the hydrogen bonding patterns.

Topics: Calixarenes; Hydrogen Bonding; Models, Chemical; Molecular Conformation; Phenols; Solutions; Thiourea

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.

Topics: Calixarenes; Concanavalin A; Glycoconjugates; Hydrogen Bonding; Molecular Conformation; Nephelometry and Turbidimetry; Organophosphorus Compounds; Peanut Agglutinin; Phenols; Spectrometry, Mass, Electrospray Ionization; Substrate Specificity; Thiourea