Polymer glycosylations

S. G. Withers, Mechanisms of glycosyl transferases and hydrolases, Carbohydr. Polym., 44 (2001) 325-337. 

Several methods are available to access glycosyl iodides (Scheme 2.50). Anomeric hemiacetals bearing diverse protecting groups (Bn, Bz, Ac, N3, CMe2) upon treatment with a polymer-bound triphenylphosphine-iodine complex and imidazole can be converted into a-glycosyl iodides [179]. The precipitated by-products,... 

Sulfoxide donors have been employed in the glycosylation of soluble and insoluble polymer-supported glycosyl acceptors, and the area has been reviewed [86,283]. 

High selectivity and substrate specificity of glycosyl transferases make them valuable catalysts for special linkages in polymer-supported synthesis. There is, however, still a rather limited set of enzymes available to date, and the need to synthesize a variety of natural and non-natural oligosaccharides prevails. Particularly with regard to combinatorial approaches, chemical solid-phase oligosaccharide synthesis promises to meet the demands most effectively. 

The first problem to be addressed in the solid-phase assembly of Leb involved the synthesis of the core tetrasaccharide (Scheme 2.17).25 Polymer-bound galactal 10 was epoxidized with DMDO. The resultant epoxide reacted with a solution of glucal 55 to give polymer-bound disaccharide diol 56. This reaction proceeded in a highly regioselective fashion, wherein glycosylation occurred only at the allylic C3 position... 

PEG) derivatized with a fluorenylmethanol group 75. Deprotection and glycosylation was similar to that described in Scheme 3.11. Treatment with mild base then effected p-elimination to release 79 from the polymer. 

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