Glycosylation methods

2 Synthesis of Glycosides from Anomeric Thio Derivatives 

6 Glycosyl Phosphites, Phosphates and Other Phosphorus Compounds 

11 Other Glycosyl Donors with Glycosyl-Oxygen Bonds 

4 Synthesis of Glycosides from Donors with Other Heteroatoms 

2 Glycosyl Donors with Nitrogen at the Anomeric Center 

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A conceptually new direct oxidative glycosylation with glycal donors, employing a reagent combination of triflic anhydride and diphenyl sulfoxide, has recently been reported by Gin [83], This new 3-glycosylation method works very well with hindered hydroxy nucleophiles, including sterically shielded carbohydrate hydroxy systems, and can be run on large scales. 

Moreover, the one-pot sequential glycosylation method has been applied successfully to the rapid assembly of a branched heptasaccharide 73 (Scheme 2.23) [106],... 

Wong and coworkers showed that 5-azido sialyl donors protected with O-acetyl ester are useful for a-selective glycosylations of primary hydroxyls (Scheme 4.6e) [169]. It was proposed that the linear and electron-withdrawing nature of the C-5 azido moiety stabilizes the reactive axial acetonitrile adduct to allow the incoming nucleophile to approach the a-face in an SN2-like fashion. In addition, a chemose-lective glycosylation method has been developed for the synthesis of NeuAca-(2 —> 9) NeuAc as thioglycoside donor for use in the subsequent glycosylations [169]. 

Orthoester to Glycoside Rearrangement - The Two-Stage Glycosylation Method Revisited... 

The two-stage glycosylation method (12 —> 14 —> 6, Scheme 5.15) had been introduced to avoid problems related to the competitive incorporation of the acceptor (R H) and the extruded alcohol (ROH) from 12. In this context, more efficient glycosylation strategies (4—>14—>6, Scheme 5.15), which circumvent the competitive aspect, have been studied [58]. 

The electron-withdrawing capability of the disarming substituent at the 6-position also controls the stereochemical outcome of the Crich glycosylation method. Thus, 6-mono- and difluoro substituted 5-phenyl 2,3,4-tri-0-benzyl-D-mannopyranosides 27 and 28 and the trifluoro analogue of 5-phenyl... 

F. Barresi and F. O. Hindsgaul, Glycosylation methods in oligosaccharide synthesis Modern Synthetic Methods, 1995, 7, 281. 

The first group of approaches to glycosyl phosphates, wherein the carbohydrate acts as electrophilic component, entails common glycosylation methods and... 

The requirements for new glycosylation methods outlined at the beginning of this chapter, namely convenient diastereocontrolled anomeric O-ac-tivation (first step) and subsequent efficient diasterecontrolled glycosylation promoted by genuinely catalytic amounts of a catalyst (second step), are essentially completely fulfilled by the trichloroacetimidate method. This is clearly shown by the many examples and references given in this article. In terms of stability, reactivity, and applicability toward different acceptors, the... 

The Sulfoxide Glycosylation Method and its Application to Solid-Phase Oligosaccharide Synthesis and the Generation of Combinatorial Libraries... 

Figure 3.1 Oligosaccharides synthesized using the sulfoxide glycosylation method.

It has long been recognized that polymeric supports for oligosaccharide synthesis do not need to be insoluble.33 Wang et al. applied the sulfoxide glycosylation method to the synthesis of disaccharide 79 (Scheme 3.14). The key feature of this work was the base-labile linker. Sulfoxide 74 was used to glycosylate polyethylene glycol... 

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