Active oligosaccharides

Extensive work has been done by using buta-l,3-dienyl-glycosides of unprotected sugar to study aqueous Diels-Alder reactions and to prepare optically active oligosaccharides [20]. 

Carba-trehalosamine was found to show 25% of the activity of 2-treha-losamine, which showed that, in biologically active oligosaccharides, re-... 

A different strategy for the development of carbohydrate mimics has focused on the replacement of the non-pharmacophoric parts of active oligosaccharides by conformationally stable cyclic diols. Thus, looking for an analogue of the a-o-Man/)-(l — 2)-a-D-Man/>-(l — 6)-a-D-Man/)-mannotrioside, one of the terminal arms of the MangGlcNAc2... 

The 3-C-sulfated D-glucosaminyl-N-sulfate residue has been found only in active oligosaccharides. 

This review presents a brief account on the conformation of biologically active oligosaccharides. Emphasis will be put on the conformational analysis of heterooligomers. The conformational preferences of some disaccharides will be included for reference purposes. Conformational aspects of homo-oligomers and homopolymers will not be discussed. 

The dogma that glycoproteins occur exclusively in eucaryotic cells had to be revised in the last twenty years. Bacterial glycoproteins form the outer surface (S)-layer of archae- and eubacteria [61,62]. In analogy to eucaryotic cells, partly sulfated oligosaccharides attached to Asn or Thr are found in halobacteria. Nucleoside-diphosphate-activated oligosaccharides were identified as intermediates in the biosynthesis of the S-layer of the eubacterium Bacillus alvei [63] and the archaebacterium Methanothermus fervidus [64],... 

Squaric acid esters (Fig. 5a) sometimes are used to link glycans to proteins (52, 54—56). A-Acetyl-chito-oligosaccharides were linked to silk fibroin by reacting solubilized siUc fibroin with cyanuric chloride-activated oligosaccharides (Fig. 5b). 

Another significant development regarding the exploration of biological functions and specific chemical reactivity of 1,2-dithiolanes is directed toward the synthesis of biologically active oligosaccharides and peptide derivatives that contain this five-membered cyclic disulfide. 

SCHEME 27. Steric hindrance-facilitated synthesis157 of phytoalexin-elicitor active oligosaccharide 149. 

R. Geurtsen, F. Cote, M. G. Hahn, and G.-J. Boons, Chemoselective glycosylation strategy for the convergent assembly of phytoalexin-elicitor active oligosaccharides and their photoreactive derivatives, /. Org. Chem., 64 (1999) 7828-7835. 

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