BrOnsted acids glycosylation

Classically, Bronsted acids are the promoters of the Fischer glycosylation. Though substrate complexity is still limited in scope, recent developments in these reagents more commonly allows for disaccharide synthesis (Scheme 3.3). For instance, Koto et al. have reported that the combination of methanesulfonic acid (30 mol%) and... 

In addition to Bronsted acid promoted Fischer-type glycosylations, Lewis acids have been investigated (Scheme 3.4). A variety of Lewis acids promote glycosylation under mild conditions, often in substoichiometric amounts. The earliest examples include ZnCl2 [18] and FeCl3 [19], although these readions were demonstrated only for preparation of trehalose-type disaccharides. Mukaiyama et al. have very recently developed metal triflate catalysts for the dehydrative glycosylation with... 

Representative Procedure for Bronsted Acid Promoted Glycosylation with Cl-Hemiacetal Donors Using Methoxyacetic Acid [11]... 

The combination of dicyclopentadienylzirconium dichloride and silver perchlorate activates armed glycosyl sulfoxides in dichloromethane between -20 °C and room temperature, but only very simple acceptors were studied [335]. Other Lewis and Bronsted acids studied include the environmentally benign europium, lanthanum and ytterbium triflates [336], certain polyoxometallates [337], sulfated zirconia [338] and Nafion H [338]. 

Cox DJ, Smith MD, Fairbanks AJ (2010) Glycosylation catalyzed by a chiral Bronsted acid. Org Lett 12 1452... 

Jamison and coworkers reported on the one-flow, two-step synthesis of nucleosides by Bronsted acid catalyzed glycosylation and base-promoted deprotection [6]. The first glycosylation was carried out by treating protected ribofuranose with silyl-protected thymine in the presence of 5 mol% of pyridinium triflate in acetonitrile. The formed glycosylated product was then treated with methanolic sodium meth-oxide (0.15 M) for deprotection, yielding the desired nucleoside in 94% yield (Scheme 5.6). 

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