Single-Step Per-O-Sulfonation of Sugar Oligomers with Concomitant 1,6-Anhydro Bridge Formation for Binding Fibroblast Growth Factors

Many circulating cancer-related proteins, such as fibroblast growth factors (FGFs), associate with glycosaminoglycans-particularly heparan sulfate-at the cell surface. Disaccharide analogues of heparan sulfate had previously been identified as the shortest components out of the sugars that bind to FGF-1 and FGF-2. Taking note of the typical pose of l-iduronic acid, we conceived of per-O-sulfonated analogues of such disaccharides, and devised a single-step procedure for per-O-sulfonation of unprotected sugars with concomitant 1,6-anhydro bridge formation to achieve such compounds through direct use of SO₃ ⋅Et₃ N as sulfonation reagent and dimethylformamide as solvent. The synthesized sugars based on the oligomaltose backbone bound FGF-1 and FGF-2 mostly at the sub-micromolar level, although the tetrasaccharide analogue achieved low-nanomolar binding with FGF-2.