Direct glycosylation

T. Chandra and K. L. Brown, Direct glycosylation Synthesis of a-indoline ribonucleosides, Tetrahedron Lett., 46 (2005) 2071-2074. 

The biological significance of glycoporphyrins, their limited natural occurrence, and their widespread applications have made the availability of such compounds a scientific challenge for several research groups. Synthetic approaches have consisted in the direct glycosylation of prefunctionalized porphyrins or chemical synthesis from suitable glycoconjugates precursors. 

Scheme 4.24 Two-directional glycosylations with tritylated thioglycosides.

Scheme4.25 The preparation ofthe Galili pentasaccharide using thioglycosyl donors and acceptors in a two-directional glycosyl-ation strategy.

Soluble polyethylene glycol (PEG) as polymer support was also successfully investigated. Precipitation after each reaction step in order to remove excesses of reagents and soluble byproducts seemed to work well. Another topic of great interest is direct glycosylation of solid support connected peptides in order to arrive finally at glycopeptides. (9-Glycosyl trichloroacetimidates also proved successful in this endeavor. 

Scheme 10.9 Synthesis of a trisaccharide library on solid support using a two-directional glycosylation approach.

Scheme 13.19 Direct glycosylation of preformed peptides on solid phase.

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