Multiple and regioselective introduction of protected sulfates into carbohydrates using sulfuryl imidazolium salts

Selective incorporation of trichloroethyl (TCE)-protected sulfates into monosaccharides was examined using reagent 2. In general, sulfation of 4,6-O-benzylidene acetals of galactosides and glucosides (2-OH versus 3-OH sulfations) proceeded in good to excellent yield and selectivity. Sulfation occurred predominantly at the 2-OH in 4,6-O-benzylidene acetals of alpha-glucosides and at the 3-OH in 4,6-O-benzylidene acetals of beta-galactosides and beta-glucosides. Good yields and selectivity was also achieved for the 3-OH in 3,4-diols of glucosides and galactosides. A glucoside bearing a 2-amino moiety and 6-OH group gave mainly the N-sulfated product in good yield. Selective sulfation of the primary 6-OH in galactose and glucose derivatives bearing one or two free secondary hydroxyl groups was also achieved usually in good yield and selectivity. Reagent 2 was also effective for the direct disulfation of diols of glucosides and galactosides, and trisulfated monosaccharides could be prepared from the disulfated compounds.