Tunable Activation of Glycosyl Trichloro- and (N-phenyl)trifluoro­acetimidates with Ytterbium(III) Triflate: One-Pot Synthesis of ­Trisaccharides under Catalytic Conditions

A mild promoter such as Yb(OTf)3 allows selective activation of glycosyl trichloroacetimidate building blocks in the presence of glycosyl (N-phenyl) trifluoroacetimidates with a similar pattern of protecting groups. This selectivity has been exploited in the one-pot assembly of two different trisaccharides in good overall yields. In contrast to other reported procedures, a catalytic amount of promoter is sufficient to trigger both glycosidation steps of the sequential process.