Dendrophanes: Water-soluble dendritic receptors - Preliminary communication

The dendritic cyclophanes (dendrophanes 1-3 containing a [6.1.6.1]paracyclophane as the initiator core embedded in dendritic poly(ether-amide) shells of first (1), second (2), and third (3) generation were prepared and characterized. The X-ray crystal-structure analyses of esters 7 and 4, derivatives of cyclophane core 9 and first-generation dendrophane 1, respectively, displayed open cavity binding sites suitable for the inclusion complexation of aromatic substrates. with their carboxylate surface groups, dendrophanes 1-3 were readily soluble in aqueous phosphate buffer (pH 8.0), and the complexation of naphthalene derivatives was investigated by H-1-NMR and fluorescence titrations. The binding studies demonstrated that the cyclophane cavity remains open and accessible to appropriate substrates even at higher dendritic generations. The 1:1 complexes formed in aqueous buffer were of similar stability to those formed by the unbranched core 9 (K-n between 1000 and 10000 1 mol(-1), 300 K). investigations with the fluorescent probe 6-(p-toluidino)naphthalene-2-sulfonate (12) showed that the micropolarity at the dendrophane core decreases with increasing generation number.