Synthesis glycosidic linkages

In order to determine if this lack of significant enzymatic activity was related to the steric hindrance or to the nature of the carbamate ester glycosidic linkage, synthesis of the bis-carbamate prodrug 52 was undertaken [63]. 

The synthesis of (3-D-fructofuranosides is yet another useful application of this concept [293-295]. The latter 1,2-cis-glycosidic linkage is as difficult to establish as in the case of (3-mannosides. In an elegant synthesis of a-D-fucofuranose-containing disaccharides, Plusquellec and coworkers used the IAD concept via p-methoxybenzylidene acetals in combination with a glycosylation protocol via pentenyl glycosides. Here, the intermediate NIS-adduct could be isolated (Scheme 5.108) [295]. 

It is of interest that similar enzymes, capable of exchanging glycosidic linkages, appear to be involved in the synthesis of some polysaccharides. Thus the polysaccharide dextran is formed from sucrose by enzyme preparations from Leuconostoc46 while the polysaccharide levan is produced from sucrose or raffinose by enzymes of other bacteria.49 The reactions may be written as follows ... 

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