2-Deoxy -glycosides, synthesis

The glycals are easily converted into the 1,2-dihalo-derivatives, which in principle can act as glycosyl donors. However, these derivatives have not found wide application in glycoside synthesis, mainly because of the low facial selectivity in the initial addition of the electrophilic species [143-145]. In an example of a successful application, 2-deoxy-2-bromo-a-D-glucopyranosyl bromide [146] has been shown to give predominantly the 2-deoxy-P-D-glucopyranosides in silver-triflate-promoted reactions with alcohols. 

A reaction which is analogous to the orthoester synthesis but which utilises glycosyl oxazolines affords means of synthesising, 2-trans-2 amino-2-deoxy-glycoside derivatives. Treatment of the gluco compomd (17) with phenol in the presence of toluene- -sulphonic acid thus gave the glycoside (18), and it was also utilised in a nucleoside synthesis 48). 

It is also appropriate to recognize the role of enolates stabilized by an exocyclic carbonyl function in C-glycoside synthesis. The use of LN to achieve reductive cleavage of anomeric sulfones to provide access to an ester-stabilized enolate and, ultimately, 2-deoxy- -C-glycosides has already been illustrated in Scheme 11 (Sect. 2.1.1). 

Nicolaou KC, Mitchell HJ, Flyaktakidou KC, Suzuki H, Rodriguez RM, 1,2-Seleno migrations in carbohydrate chemistry Solution and solid-phase synthesis of 2-deoxy glycosides, orthoesters, and allyl orthoesters, Angew. Chem. Int. Ed., 39 1089-1093, 2000. 

Although not all of the listed promoters have been applied to the synthesis of 2-deoxy glycosides it is reasonable to assume that they can also be used for this purpose... 

Nicolaou, K C, Fylaktakidou, K C, Mitchell, H J, van Delft, F L, Rodriguez, R M, Conley, S R, Jin, Z, Total synthesis of eveminomicin 13,384-1 — part 4 explorations of methodology stereocontrolled synthesis of l,T-disaccharides, 1,2-seleno migrations in carbohydrates, and solution- and solid-phase synthesis of 2-deoxy glycosides and orthoesters, Chem. Eur. J., 6, 3166-3185, 2000. 

Bai, Y, Boons, G-J, Burton, A, Johnson, M, Haller, M, Vinyl glycosides in oligosaccharide synthesis (part 6) 3-buten-2-yl 2-azido-2-deoxy glycosides and 3-buten-2-yl 2-phthalimido-2-deoxy glycosides as novel glycosyl donors, J. Carbohydr. Chem., 19, 939-958, 2000. 

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