Fusion Warren, Danishefsky, and coworkers used chemical ligation to create a bifunctional glycopeptide by combining two glycopeptides, each containing a different carbohydrate. In a preceding step, each of the two glycopeptides was made by adding an oligosaccharide to a peptide immediately before ligation. Asterisks indicate asymmetric centers that cause oligosaccharides to each adopt two different stereochemical forms. Courtesy of J. David Warren |