A stereoselective glycosidation using thioglycosides, activation by combination of N-bromosuccinimide and strong acid salts

Article abstract of DOI:10.1016/0040-4020(95)98690-J

A stereoselective glycosidation with thioglycosides was effected under mild and neutral conditions by combined use of N-bromosuccinimide (NBS) and a catalytic amount of various strong acid salts. A combination of NBS with Ph₂IOTf, Bu₄NOTf, or Bu₄NClO₄ was advantageous for β-selective glucosidation with 2-O-acylated or 2-O-benzylated donors by virtue of either the neighboring group participation or the known solvent effect of nitrile, respectively. α-Selective glucosidation was effected by the use of a 2-O-benzylated donor in the presence of LiClO₄ or LiNO₃ as a catalyst in ether. Addition of silica gel to the reaction mixture increased both the α-selectivity and reaction rate.