Cu–Al mixed oxide-catalysed multi-component synthesis of gluco- and allofuranose-linked 1,2,3-triazole derivatives

A series of carbohydrate-linked 1,2,3-triazole derivatives were synthesized in good yields from glucofuranose and allofuranose diacetonides using as key step a three-component 1,3-dipolar azide–alkyne cycloaddition catalysed by a Cu–Al mixed oxide. In this multi-component reaction, Cu–Al mixed oxide/sodium ascorbate system serves as a highly reactive, recyclable and efficient heterogeneous catalyst for the regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles. The reported protocol has significant advantages over classical CuI/ N , N -diisopropylethylamine (DIPEA) or CuSO 4 /sodium ascorbate conditions in terms of efficiency and reduced synthetic complexity. In addition, the selective deprotection of synthesized di- O -isopropylidene derivatives was also carried out leading to the corresponding mono- O -isopropylidene products in moderate yields. Some of the synthesized triazole glycoconjugates were tested for their in vitro antimicrobial activity using the disc diffusion method against Gram-positive bacteria ( Staphylococcus aureus and Bacillus subtilis ), Gram-negative bacteria ( Escherichia coli and Pseudomonas aeruginosa ), as well as fungus ( Aspergillus niger ) and yeast ( Candida utilis ). The results revealed that these compounds exhibit moderate to good antimicrobial activity mainly against Gram-negative bacteria.