Thioglycosides trifluoromethanesulfonate

To a solution of thioglycoside (1.0 equiv), Ph2SO (2.8 equiv) and TTBP (3.0 equiv) in dichloromethane (4.0 ml mmol-1) was added trifluoromethanesulfonic anhydride (1.4 equiv) at —60 °C under an argon atmosphere. The reaction mixture was... 

To a solution of thioglycoside (1.0 equiv), 1-benzenesulfinyl piperidine (1.0 equiv), TTBP (2.0 equiv), and freshly activated 3 A powdered molecular sieves in dichloromethane (25.0 ml mmol-1) was added trifluoromethanesulfonic anhydride (1.1 equiv) at —60 °C under an argon atmosphere. The reaction mixture was stirred for 5 min, after that a solution of the glycosyl acceptor (1.5 equiv) in dichloromethane (4.0 ml mmol-1) was added. The reaction mixture was stirred at — 60 °C for 2 min, after that it was slowly warmed to room temperature and quenched by the addition of saturated aqueous NaHC03. The organic layer was washed with brine, dried (MgS04), filtered and the filtrate was concentrated to dryness. Purification of the crude product by column chromatography over silica gel afforded the product. 

Lonn, H, Glycosylation using a thioglycoside and methyl trifluoromethanesulfonate — a new and efficient method for cis and trans glycoside formation, J. Carbohydr. Chem., 6, 301-306, 1987. 

Crich, D, Smith, M, 5 -(4-Methoxyphenyl) benzenethiosulfinate (MPBT)/trifluoromethanesulfonic anhydride a convenient system for the generation of glycosyl triflates from thioglycosides, Org. Lett., 2, 4067-4069, 2000. 

Crich, D, Smith, M, 1-Benzenesulfinyl piperidine/trifluoromethanesulfonic anhydride a potent combination of shelf-stable reagents for the low-temperature conversion of thioglycosides to glycosyl triflates and for the formation of diverse glycosidic hnkages, J. Am. Chem. Soc., 123, 9015-9020, 2001. 

Ldnn, H, Sulfurylchloride trifluoromethanesulfonic acid — a novel promoter system for glycoside synthesis using thioglycosides as glycosyl donors, Glycoconjugate J., 4, 117-118, 1987. 

Kallin, E, Lonn, H, Norberg, T, Glycosidations with thioglycosides activated by suUuryl chloride trifluoromethanesulfonic acid — synthesis of a human-blood group-B trisaccharide glycoside, Glycoconjugate J., 5, 3-8, 1988. 

Initially, the method was based on the differential reactivity conferred on each of the partners by the nature of the protecting groups and by the intrinsic nucleophilicity of the thioaryl leaving groups. However, as the method evolved, it became clear that the choice of the promoter was also an important factor to take into consideration. Indeed, it was demonstrated that a disarmed thioglycoside could be activated in the presence of powerful thiophilic promoters such as A-iodosuccinim-ide/trifluoromethanesulfonic acid (NIS/TfOH), whereas it remained inactivated in the presence of weak thiophilic reagent such as iodonium dicollidine perchlorate or methyl triflate [43,45]. 

Crich D, Banerjee A, Li W, Yao Q. Improved synthesis of 1-benzenesulfinyl piperidine and analogs for the activation of thioglycosides in conjunction with trifluoromethanesulfonic anhydride. J Carbohydr Chem 2005 24 415-424. 

In the view of the well-known reaction of thioglycosides with NBS (77-bromosuccinimide), which generates the unstable cationic species 31 in the course of formation of oxocarbenium ion 32 (Fig. 5.8), Konradsson et al. [5]. reported that 77-iodosuccinimide/trifluoromethanesulfonic acid induces the same reactivity with disarmed thioglycosides as substrates. (NIS/AgOTf or NIS/EtsSiOTf also proves to be an excellent source of iodonium ion.)... 

Methylsulfenyl trifluoromethanesulfonate (1) is an activator in the thioglycoside-mediated formation of glycosidic linkages. 

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