Model O-glycosylation reactions at either rim of calix[4]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 calix[4]arene by glycosylation of the phenolic hydroxyl groups by means of a Mitsunobu reaction. Tetrapropoxy calix[4]-arenes bearing two or four hydroxy-methyl groups at the upper rim were coupled with perbenzoylated thioethyl D-galactoside and D-lactoside in the presence of the thiophilic promoter copper(II) triflate. In this way β-linked bis and tetrakis-O-galactosyl calix[4]arenes 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 calix[4]arenes (calixsugars)
DONDONI, Alessandro;MARRA, Alberto;
1997
Abstract
Model O-glycosylation reactions at either rim of calix[4]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 calix[4]arene by glycosylation of the phenolic hydroxyl groups by means of a Mitsunobu reaction. Tetrapropoxy calix[4]-arenes bearing two or four hydroxy-methyl groups at the upper rim were coupled with perbenzoylated thioethyl D-galactoside and D-lactoside in the presence of the thiophilic promoter copper(II) triflate. In this way β-linked bis and tetrakis-O-galactosyl calix[4]arenes 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.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.