SuFEx: a metal-free click ligation for multivalent biomolecules

The Sulfur(vi) Fluoride Exchange (SuFEx), revived by Sharpless and co-workers from an unrecognized state, is an emerging new click reaction that is based on the high reactivity of sulfonyl fluorides and fluorosulfates with suitable nucleophiles such as silyl ethers and amines. Hence, we comment in this Perspective on the use of SuFEx for the synthesis of a new family of sugar containing sulfonamides from the reaction of a glycosylsulfonyl fluoride with aliphatic amines. We also highlight the applications of SuFEx to multivalent scaffolds such as tetraamino- and tetrafluorosulfonyl-calixarene leading to sulfonamide-linked sugar and iminosugar clusters. Finally, we report on the chemoselective functionalization of bovine serum albumin (BSA) which, owing to the amino group of lysine moieties, reacted with SO₂F₂ to give a multivalent BSA-SO₂F system. The PEGylation of the same protein by coupling with a PEG-fluorosulfate is described as well.