Modular Synthesis of Heparan Sulfate Oligosaccharides Having N-Acetyl and N-Sulfate Moieties

Abstract

Heparan sulfates are structurally diverse sulfated polysaccharides that reside at the surface of all animal cells where they can interact with a multitude of proteins, thereby modulating a wide range of physiological and disease processes. We describe here a modular synthetic methodology that can provide libraries of heparan sulfate oligosaccharides that have glucosamine residues modified by different patterns of N-acetyl and N-sulfate moieties. It is based on the use of glycosyl donors that are modified at C2 by an azido-or trifluoromethylphenyl-methanimine moiety, which allowed the selective installation of α-glycosides. The amino protecting groups can be selectively unmasked by a reduction or acid treatment, allowing the installation of N-acetyl and N-sulfate moieties, respectively. In combination with the orthogonal hydroxyl protecting groups levulinic (Lev) ester, thexyldimethylsilyl (TDS) ether, allyloxycarbonate (Alloc), and 9-fluorenylmethyl carbonate (Fmoc), different patterns of O-sulfation can be installed. The methodology was applied to prepare four hexasaccharides that differ in the pattern of N-and O-sulfation. These compounds, together with a number of previously prepared HS oligosaccharides, were printed as a glycan microarray to examine the binding selectivities of several HSbinding proteins.

Heparan Sulfate Biosynthesis and Sulfation Profiles as Modulators of Cancer Signalling and Progression

“…Many studies in this field, that have been performed to infer about structural-functional relationships, resorted to artificial in vitro models, via binding assays and using heavily sulfated heparin molecules and short HS-like oligosaccharides, with the purpose of unravelling bioactive sulfation arrangements and distinctive protein-binding sites within HS chains ( 70 , 148 , 149 ). However, structural differences between these molecules and full-length cellular HS chains might lead to deceitful results, since the use of heavily sulfated heparin might mask specific binding sites and HS oligosaccharides are not presented as embedded in a full-length HS chain.…”

Developments in the Chemical Synthesis of Heparin and Heparan Sulfate

“…In 2020 Boons and colleagues presented a modular approach to access HS oligosaccharides containing both d ‐GlcNAc and d ‐GlcNS units [44] . A previous modular synthetic route from the group provided a diverse range of HS oligosaccharides from two common disaccharide building blocks, 114 and 115 (Scheme 16A), [45] but did not deliver sequences containing both d ‐GlcNS and d ‐GlcNAc.…”

State‐of‐the‐art glycosaminoglycan characterization

“…In another approach GlcN residues were modified by different patterns of N ‐acetyl and N ‐sulfate moieties using azido‐ or trifluoromethylphenyl‐methanimine‐modified glycosyl donors. Together with the orthogonal hydroxyl protecting groups levulinic ester, thexyldimethylsilyl ether, allyloxycarbonate, and 9‐fluorenylmethyl carbonate, different O ‐sulfation modification patterns were constructed (Sun et al, 2020). Recently, a modular synthetic approach providing structurally diverse HS oligosaccharides with and without 3‐OS was carried out.…”