Stereoselective Glycosylation of Thioglycosides Promoted by Respective Combinations of N-Iodo-or N-Bromosuccinimide and Trityl Tetrakis(pentafluorophenyl)borate. Application to One-Pot Sequential Synthesis of Trisaccharide

摘要

New highly effective promoter system for the glycosylation of thioglycoside, the combined use of stoichiometric amount of either N-iodosuccinimide or N-bromosuccinimide and a catalytic amount of TrB(C_6F_5)_4, was developed and was successfully applied to the one-pot sequential synthesis of trisaccharides. In the first glycosylation step, 3,4,6-tri-O-benzyl-2-O-p-toluoyl-#beta#-D-glycopyransoyl phenylcarbonate was treated with thioglycosides in the presence of a catalytic amount of TrB(C_6F_5)_4 alone, and the following glycosylation with methyl #alpha#-D-glycosides was carried out by further addition of either N-iodosuccinimide or N-bromosuccinimide to the initially resulted reaction mixture to afford the corresponding trisaccharides in one-pot manner.