A convergent and efficient strategy for the synthesis of high-mannose oligosaccharides is described wherein regioselective glycosylations between trichloroacetimidate donors and partially protected acceptors are employed to reduce the number of protection–deprotection steps. Two representative branched mannose oligosaccharides, a mannose heptasaccharide (Man7) and a mannose nonasaccharide (Man9) were constructed via (4 + 3) and (5 + 4) glycosylations, respectively. These mannose-containing oligosaccharides were obtained in nine steps in ∼25% overall yield and >98% purity on 60–70 mg scales to demonstrate the effectiveness of the strategy.
Meng, B., Wang, J., Wang, Q., Serianni, A. S., & Pan, Q. (2017). Rapid assembly of branched mannose oligosaccharides through consecutive regioselective glycosylation: A convergent and efficient strategy. Tetrahedron, 73(27–28), 3932–3938. https://doi.org/10.1016/j.tet.2017.05.073