Stereocontrolled preparation of biotinylated chondroitin sulfate E di-, tetra-, and hexasaccharide conjugates

• The oligomers were built by iterative coupling reactions using a single precursor.
• Biotinylated conjugates were prepared from oligomers equipped with a spacer.
• Radical reduction of the N-trichloroacetyl groups was achieved using ABCN.
• A side-reaction was observed on the carbonyl group of the levulinate ester.

The synthesis of biotinylated conjugates of oligomers of the basic repeating unit of chondroitin sulfate E (CS-E) with the sequence [GlcA-4,6-disulfated GalNAc]n is reported herein for the first time. An efficient and stereocontrolled preparation of di-, tetra-, and hexasaccharide derivatives was achieved using a common key disaccharide intermediate in an iterative way. An unexpected and never reported side reaction on the carbonyl group of the levulinate ester was observed during a coupling reaction. These complex molecules should be useful to study their interactions with various proteins.

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