Efficient and stereocontrolled synthesis of chondroitin mono- and disaccharide linked to variously sulfated biotinylated trisaccharides of the linkage region of proteoglycans

Synthesis of oligosaccharides of the linkage region of proteoglycans using regioselective glycosylation

Proteoglycans (PGs) are complex macromolecules that are composed of glycosaminoglycan (GAG) chains covalently attached to a core protein through a tetrasaccharide linker. Biosynthesis of PGs is complex and involves a large number of glycosyltranferases. We report herein for the first time the synthesis of a collection of various sulfoforms of the disaccharide GlcA-1,3-β-d-Gal and trisaccharides GlcNAc-1,4-α-d-GlcA-1,3-β-d-Gal and GalNAc-1,4-β-d-GlcA-1,3-β-d-Gal using a regioselective glycosylation. Preliminary results on the impact of sulfation of these disaccharides upon recombinant chondroitin sulfate N-acetylgalactosaminyltransferase-1 (CSGalNAcT-1) involved in chondroitin sulfate chain initiation is also reported.

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

Here, we present an exploratory study on the fluorous-assisted synthesis of chondroitin sulfate (CS) oligosaccharides. Following this approach, a CS tetrasaccharide was prepared. However, in contrast to our previous results, a significant loss of β-selectivity was observed in [2 + 2] glycosylations involving N-trifluoroacetyl-protected D-galactosamine donors and D-glucuronic acid (GlcA) acceptors. These results, together with those obtained from experiments employing model monosaccharide building blocks, highlight the impact of the glycosyl acceptor structure on the stereoselectivity of glycosylation reactions. Our study provides useful data about the substitution pattern of GlcA units for the efficient synthesis of CS oligomers.

An Approach to Synthesize Chondroitin Sulfate-E (CS-E) Oligosaccharide Precursors

An approach was developed to synthesize chondroitin sulfate-E (CS-E) oligosaccharides by adopting a postglycosylation-transformation strategy: different from all of the traditional approaches, the characteristic groups of CS-E were introduced following the assembly of the oligosaccharides. The adjusted strategy rendered an easy chain elongation strategy. All of the elongation steps generated high yields with excellent glycosylation outcomes. An orthogonally protected disaccharide was used as the building block to provide flexibility for the group transformation and derivatization at the N-2 position of the GalNAc residue and the O-1,5 positions of the GlcA residue, thereby providing ready access for the further examination of the structure-activity relationship (SAR) of CS-E molecules.

Synthesis of Chondroitin Sulfate A Bearing Syndecan-1 Glycopeptide

Syndecan-1 chondroitin sulfate glycopeptide was synthesized for the first time using the cassette approach. The sequence of glycosylation to form the octasaccharide serine cassette was critical. The glycopeptide was successfully assembled via a 2+ (3 + 3) glycosylation strategy followed by peptide chain elongation.