A Modular System for the Synthesis of Complex N ‐Glycans

Double regioselective glycosylation is the key to the generally applicable strategy by which two triantennary octasaccharides and the tetraantennary nanasaccharide 1 are available. A modular system of oligosaccharides building blocks is the basis of an efficient synthesis of complex N-glycans with the desired number of branches in unexpectedly high yields.