Recent applications of thiol–ene coupling as a click process for glycoconjugation

There has been over the past decades a resurgence of the free-radical thiol–ene coupling (TEC) as a method for assembling crosslinked networks and polymer functionalization. On the other hand the use of TEC in carbohydrate chemistry, a field of special importance due to the key role of carbohydrates in living organisms, is represented only by a handful of papers. Nevertheless it appears that TEC possesses many if not all the attributes of a click process proceeding with the assistance of the greenest catalyst such as visible light. This tutorial review focuses on the application of TEC on different topics, all related to glycochemistry, including: (a) carbohydrate modification, (b) oligosaccharide and glycosyl amino acid synthesis, (c) assembly of glycoclusters on rigid molecular platforms (calixarene, cyclodextrin, silsesquioxane, dendrimer), (d) peptide and protein glycosylation. Also the very recent development in peptide glycosylation by the closely related thiol–yne chemistry is described.