n-Pentenyl-Type Glycosides for Catalytic Glycosylation and Their Application in Single-Catalyst One-Pot Oligosaccharide Assemblies.

We have developed a new type of n-pentenyl-type glycosides that can be activated by catalytic amounts of promoter, Hg(NTf2)2 or PPh3AuCl/AgNTf2, at room temperature. The mild activation conditions and outstanding stability of common protection/deprotection manipulations enable the enynyl donors to have broad applications in constructing various glycosidic bonds. Furthermore, under the Hg(NTf2)2-catalyzed conditions, the sequential activation of different types of donors was achieved, based on which a gentiotetrasaccharide was synthesized via the newly developed single-catalyst one-pot strategy.

Stereoselective ß-Mannosylation with 2,6-Lactone-bridged Thiomannosyl Donor by Remote Acyl Group Participation.

Stereoselective ß-mannosylation has been recognized as one of the greatest challenges of carbohydrate chemistry. Herein, we described a practical method for stereoselective construction of ß-mannosides by using a 2,6-lactone-bridged thiomannosyl donor through the remote acyl-group participation as well as the steric effect of O-4 substituent. The two effects are enabled through the conversion of a regular mannopyranosyl 4 C1 conformation into a 2,6-lactone bridged conformation. The lactone donor could be readily prepared in three steps on a gram scale and the ß-mannosylation proceeded smoothly with high stereoselectivity for primary, secondary and tertiary alcohol acceptors. In addition, this strategy was successfully applied to the synthesis of a naturally occurring trisaccharide.