Chondroitin sulfate (CS) is a liner sulfated polysaccharide belonging to glycosaminoglycan (GAG) super family, and is widely distributed in various tissues as components of cell membrane and extracellular matrix. CS structure is composed of repeating disaccharide unit consisting of glucuronic acid (GlcA) and N-acetylgalactosamine (GalNAc). CS is often sulfated heterogeneously due to the multiple and random enzymatic modifications in the biosynthesis. Recently, the specific microstructure in CS chain is responsible for the specific interaction with CS-binding protein. The elucidation of the structure-activity relations of CS with CS-binding protein at the molecular level is important issue. Structurally defined oligosaccharides are therefore required to analyze their biofunctions. Previously, we achieved the synthesis of all 16 kinds of disaccharide structure by systematic synthetic strategy. In this study, to further investigate binding property of CS, we carried out chemical synthesis of CS tetrasaccharide partial structures and their ligand conjugates containing dimeric CS units. Synthetic strategy is shown in Figure 1. We newly designed disaccharide building block 1, which has orthogonally removable protective groups for sulfation and elongation. Pentasaccharide precursors 4 were obtained by the glycosylation of appropriate glycosy donors 2 and acceptors 3 derived from the building block 1. Pentasaccharides 5 were prepared by selective deprotection and sulfation followed by removal of benzylic protective group. Thereafter, reductive amination of penatasaccharides 5 afforded CS ligand conjugates 6 such as CS-C+D, C+E, D+D, D+T, E+A, E+C, E+D, and E+E. Binding analysis of CS ligand conjugates with GAG-binding proteins by surface plasmon resonance (SPR) imaging, which permits their real-time study without further labeling. As a result, when basic fibroblast growth factor 2 (FGF-2) was tested, specific binding interactions were clearly observed with CS-D+T, E+A, E+C, E+D and E+E. References: 1) Wakao M.; Obata R.; Miyachi K.; Kaitsubata Y.; Kondo T.; Sakami C.; Suda, Y. Bioorg. Med. Chem. Lett. 2015, 25, 1407–1411. 2) Miyachi K.; Wakao, M.; Suda, Y. Bioorg. Med. Chem. Lett. 2015, 25, 1552–1555.

Synthesis of chondroitin sulfate partial structure and interaction analysis with GAG-binding proteins by SPR imaging

251st National Meeting (2016)

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