Glycosidations on a Solid Phase

The subject of oligosaccharide synthesis on a solid phase has recently been reviewed.183 

Despite these considerations, there has been substantial progress in recent years in the synthesis of oligosaccharides on a solid phase. Since the central issue here is glycosidation, this topic is the current focus. An obvious decision at the outset is the mode of linkage of the saccharide oligomer to the solid phase, either attachment at the anomeric center, or attachment to the polymer through one of the other positions. This question is illustrated in the following two examples. 

The second example is a solid-phase synthesis of a heptasaccharide phytoalexin elicitor. Here, attachment of the polymer was to the reducing end of the oligosaccharide. The structure was chosen as an example for the development of 

A seven-step synthesis, from the starting materials A-C and the polystyrene-bound starting monomer unit proceeded in 20% yield. Each step involved condensation and chemospecific deprotection at a single position.191 

The fully protected heptasaccharide was finally removed, photochemically in tetrahydrofuran, from the solid support, deacylated with sodium methoxide in tetrahydrofuran-methanol, and finally debenzylated by hydrogenolysis with Pd/C in methanol to yield the deprotected target heptasaccharide.191 

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