Synthesis and polymerization, of anhydro sugar

C. Schuerch, Synthesis and polymerization of anhydro sugars, Adv. Carbohydr. Chem. Biochem., 39 (1981) 157-212. 

Y. S. Choi, T. Uryu, and T. Yoshida, Synthesis of block copolysaccharides by ring-opening polymerization of anhydro sugar derivatives, Macromol. Chem. Phys., 198 (1997) 2875-2888. 

Polymerization of anhydro sugars is aimed at the synthesis of models of naturally occurring polysaccharides and the preparation of polysaccharides resembling natural products. We briefly summarize the chemical structures of major natural polysaccharides1. 

The synthesis of other anhydro sugar derivatives is usually accomplished by an internal displacement of a leaving group with inversion, as has already been emphasized for those anhydrides in which the anhydride bridge engages the anomeric position. Three such compounds that have been used in polymerizations deserve specific mention 5,6-anhydro-l,2-0-isopropylidene-a-D-glucofuranose,12 13 its 3-methyl ether,11 and 3,5-anhydro-l,2-0-isopropylidene-a-D-xylo-furanose,14 all of which were synthesized by p-toluenesulfonylation of the primary hydroxyl group of the parent, isopropylidene derivative, followed by treatment with base. 

M. Okada, Y. Yamakawa, and H. Sumitomo, Chemical synthesis of (1 3)-/i-D-glucopyranan by ring-opening polymerization of a 1,3-anhydro sugar derivative, Macromolecules, 24 (1991) 6797-6799. 

M. Ogawa, K. Hatanaka, and T. Uryu, Synthesis of a novel cellulose-type hexopyranan 6-deoxy-(l - 4)-u-L-talopyranan by selective ring-opening polymerization of 1,4-anhydro sugar derivatives, Macromolecules, 24 (1991) 987-992. 

The validity of the approach was first demonstrated by the synthesis of a linear tetrasaccharide [22] and a hexasaccharide 13 [23] as outlined in Scheme 3. Polymer-bound galactal 5 was converted to the 1,2-anhydro sugar 6 by epoxidation with 3,3-dimethyldioxirane [24], Polymer-bound 6 acted as a glycosyl donor when reacted with a solution of 7 in the presence of zinc chloride, resulting in the formation of disaccharide 8a. Upon repetition, this glycosylation procedure accommodated the secondary alcohol glycosyl acceptor 10 as well as disaccharide acceptor 12. Huor-idolysis with tetrabutylammonium fluoride (TBAF) was used to cleave the desired products from the polymeric support and furnish hexasaccharide 13 in 29% overall yield from 5 [16]. 

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