Abstract
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 CuSO4/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.
Highlights
1,2,3-Triazole and its derivatives are an important class of nitrogen-containing aromatic heterocyclic compounds and have become one of the most relevant topics in modern heterocyclic chemistry [1]
In continuation with our interest in the synthesis of functional triazole derivatives [27,28,29,30], and in order to introduce the use of mixed oxides in carbohydrate CuAAC click chemistry, we report a rapid and facile synthesis of a series of carbohydrate-linked 1,2,3-triazole derivatives using as key step a three-component 1,3-dipolar azide–alkyne cycloaddition catalysed by Cu–Al mixed oxide, and an insight into their antimicrobial properties
The synthetic strategy adopted for the synthesis of 1,2,3-triazole–carbohydrate conjugates began with the preparation of 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose 1, which can be obtained through the acetonide protection of the cheap and readily available D-glucose [31]
Summary
1,2,3-Triazole and its derivatives are an important class of nitrogen-containing aromatic heterocyclic compounds and have become one of the most relevant topics in modern heterocyclic chemistry [1]. Click chemistry has great potential for use in binding between nucleic acids, lipids, proteins and carbohydrates In this context, metabolic glycoengineering allows direct modification of living cells with substrates for click chemistry either in vitro or in vivo, becoming a powerful tool for cell transplantation and drug delivery [20]. Metabolic glycoengineering allows direct modification of living cells with substrates for click chemistry either in vitro or in vivo, becoming a powerful tool for cell transplantation and drug delivery [20] In this sense, carbohydrates represent versatile starting substrates for the CuAAC reaction because it is possible to synthesize from them both from the azide- or the terminal alkyne-containing moieties needed for this cycloaddition reaction. In continuation with our interest in the synthesis of functional triazole derivatives [27,28,29,30], and in order to introduce the use of mixed oxides in carbohydrate CuAAC click chemistry, we report a rapid and facile synthesis of a series of carbohydrate-linked 1,2,3-triazole derivatives using as key step a three-component 1,3-dipolar azide–alkyne cycloaddition catalysed by Cu–Al mixed oxide, and an insight into their antimicrobial properties
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