Oligosaccharide assembly

Scheme 2.7 Oligosaccharides assembled on solid phase via glycal assembly. The asterisk denotes the achorage site of the first glycal to the solid support via SiPtfe linker.

To date, heptasaccharide 47 is the largest oligosaccharide assembled on a solid support using only monosaccharide building blocks. This turns out to be an excellent demonstration of the efficiency of the (9-glycosyl trichloroacetimidate approach. 

Encouraged by the success of the solution-phase approaches, we introduced a two-directional approach for oligosaccharide assembly on solid support. Two... 

The most commonly used glycosyl donors for oligosaccharide assembly are shown in Scheme 1 [2]. They can be divided into two groups (1) the chlorides, bromides, fluorides,... 

It was the use of NBS for NPG couplings that led to the discovery of the armed-disarmed protocol for oligosaccharide assembly [16]. Thus, it was observed that acyl-protected NPGs reacted more slowly than their alkyl-protected counterparts. These reactivity differences were analyzed, based on the inductive effect of the C-2 protecting group [18]. However, reactivity differences between substrates would not have been observed if NlS/Et3SiOTf had been the promoter because, under these conditions, both NPGs would have reacted by the time the TLC sample had been taken. 

Scheme 4 Rapid and efficient iterative oligosaccharide assembly using MOP- and TOPCAT-leaving groups.

Premathilake, H. D. Demchenko, A. V. In Reactivity Tuning in Oligosaccharide Assembly, Fraser-Reid, B., Lopez, J. C., Eds. Topics in Current Chemistry 301 Springer Berlin, 2011, pp. 189-221. 

FIGURE 7.1 Synthetic strategies for oligosaccharide assembly on solid support, (a) Donor-bound strategy, (b) Acceptor-bound strategy, (c) Bidirectional strategy. 

Grice, P, Ley, S V, Pietruszka, J, Osborn, H M I, Priepke, H W M, Warriner, S L, A new strategy for oligosaccharide assembly exploiting cyclohexane-1,2-diacetal methodology an efficient synthesis of a high mannose type nonasaccharide, Chem. Eur. J.,3, 431-440, 1997. 

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