Synthesis of a biotinylated keratan sulfate tetrasaccharide composed of dimeric Galβ1-4GlcNAc6Sβ

Abstract

We successfully synthesized the biotinylated keratan sulfate tetrasaccharide, Galβ1-4GlcNAc6Sβ1-3Galβ1-4GlcNAc6Sβ in a stereocontrolled manner. The suitably protected Galβ1-4GlcNPhth unit was converted to the corresponding donor and acceptor. Optimization in 2 + 2 coupling using AgOTf, CuBr₂, and n-Bu₄NBr in CH₃NO₂ at a low temperature afforded the desired tetrasaccharide that suppressed glycal formation. The subsequent chemoselective removal of the protecting group at O-6 of two GlcNAcs, sulfation, and deprotection procedures as well as biotinylation gave the target compound.

Keywords: Glycosylation; Keratan sulfate; Oligosaccharide.