Model O-glycosylation reactions at either rim of calix[il]arenes are described with the aim of providing access to a new family of carbohydrate-containing calixarene derivatives named calixsugars. One or two sugar moieties (D-mannofuranose and D-glucopyranose) were introduced at the lower rim of the parent calixarene by glycosylation of the phenolic hydroxyl groups by means of a Mitsunobu reaction, Tetrapropoxy calixarenes bearing two or four hydroxymethyl groups at the upper rim were coupled with perbenzoylated thioethyl D-galactoside and D-lactoside in the presence of the thiophilic promoter copper(Ir) triflate. In this way beta-linked bis-and tetrakis-O-galactosyl calixarenes were obtained in good yield, the latter showing some solubility in water. For the O-lactosyl derivatives only the bis-substituted compound could be obtained because of the competing formation of an intramolecular ether linkage between 1,3-hydroxymethyl groups. Preliminary binding studies showed some affinity of the galactose-containing calixsugars toward charged carbohydrates and dihydrogen phosphate anion.
Synthesis and Properties of O-Glycosyl Calixarenes (Calixsugars) / A. DONDONI; A. MARRA; M.-C. SCHERRMANN; A. CASNATI; F. SANSONE; R. UNGARO. - In: CHEMISTRY-A EUROPEAN JOURNAL. - ISSN 0947-6539. - 3(1997), pp. 1774-1782. [10.1002/chem.19970031108]