Glycosylation disaccharide synthesis

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... 

Scheme 4.70 Disaccharide synthesis by ring-closing glycosylation.

Scheme 3.14 Disaccharide synthesis using the sulfoxide glycosylation method.

H. Berber, T. Brigaud, O. Lefebvre, R. Plantier-Royon, C. Portella, Reactions of difluoroenoxysilanes with glycosyl donors Synthesis of difluoro-C-glycosides and difluoro-C-disaccharides, Chem. Eur. J. 7 (2001) 903-909. 

Scheme 3 Disaccharide synthesis with O-benzyl MOP glycosyl donors using MeOTf as catalyst.

Scheme 4 Disaccharide synthesis with 0-benzyl MOP glycosyl donors using Cu(OTf)2 as promoter.

Scheme 5 Synthesis of l,2-c -glycosyl disaccharides using MOP glycosyl donors.

R. U. Lemieux, Some implications in carbohydrate chemistry of theories relating to the mechanisms of replacement reactions, Adv. Carbohydr. Chem. Biochem. 9 1 (1954). H. Tsu-tsumi and Y, Ishido, Syntheses of 1-O-acylaldose derivatives via the corresponding O-glycosyl-pseudourcas, Carbohydr. Res. 111 75 (1982). S. Horvat, L. Varga, and J. Horvat, A new utility of O-glycosylpseudoureas for synthesis of glucopeptides and (l->6)-disaccharides, Synthesis 2J09 (1986). 

To avoid some limitations of PEGs, as for instance low loading, hyperbranched polyester such as Boltorn H40 and H50 have been successfully investigated in glycosylation reactions with 0-glycosyl trichloroacetimidates [121]. For simple mono- and disaccharide synthesis optimization of the reaction conditions led to practically quantitative transformations. 

This procedure provides a fast synthesis of C-glycosyl disaccharides with the anomeric sul-fones derived from the D-gluco, D-galacto and L-fuco series and this is presented using aldehyde 175, obtained by the five-step sequence of reactions shown in O Scheme 36. 

Anhydro sugars were first obtained by multistep synthesis, the first report of such a derivatives being by Brigl.177 Their potential as glycosyl donors was subsequently explored in disaccharide synthesis, but at that stage they did not enjoy widespread use.178-181... 

P. J. Garegg, B. Samuelsson, P. Konradsson, I. Kvamstrom, and S. C. T. Svensson, Novel glycosylation reagents synthesis of disaccharides containing 2-deoxy-2-iodo-a-D-talopyranosyl groups, Carbohydr. Res., 92 (1981) 157-159. 

A systematic investigation of the use of glycosyl acetates with trimethylsilyl triflate as activator in disaccharide synthesis has been conducted. ... 

A review of block synthesis of oligosaccharides describes glycosylation approaches and protecting group strategies and contains material of relevance in disaccharide synthesis. 

In the crucial step of the synthesis (Scheme 16), the disaccharide glycosyl donor 17 was used once again, in condensation with the acceptor 19 having two free OH groups, to produce the octasaccharide 20. This product was then converted in 7 steps via the 1-trichloroacetamido compound, analogous to the synthesis described in Scheme 15, into the final compound 21. 

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