Trehalose type

In addition to Bronsted acid promoted Fischer-type glycosylations, Lewis acids have been investigated (Scheme 3.4). A variety of Lewis acids promote glycosylation under mild conditions, often in substoichiometric amounts. The earliest examples include ZnCl2 [18] and FeCl3 [19], although these readions were demonstrated only for preparation of trehalose-type disaccharides. Mukaiyama et al. have very recently developed metal triflate catalysts for the dehydrative glycosylation with... 

Rgure 10. Synthesis of trehalose-type amino and diamino sugars having the D-manno,D-manno configuration. 

Brigl s anhydride, 3,4,6-tri-0-acetyl-l,2-anhydro-D-glucopyranose.) Two disaccbarides- [(34) and (35) ] of the trehalose type were isolated in 5.3% yield each, and a trisaccharide (36) was isolated in 8.5% yield. Higher... 

Two substituted sugars, namely 2,3-0-isopropylidene-D-lyxofuranose,8to and 2,3,5-tri-O-methyl-D-lyxofuranose,l0ab undergo polymerization during slow distillation under diminished pressure the latter formed a nonreducing dimer of the trehalose type. 

Later a number of other oligosaccharides of trehalose type were prepared.49 A trehalose, assigned the a, -configuration on the basis of Hudson s rules of isorotation,47 was prepared in 15% yield by treating a toluene solution of D-glucose tetraacetate first with zinc chloride and then with phosphorus pentoxide. 

Sharp and Stacey69 were not successful in applying the alkali salt elimination technique to the synthesis of maltose and of lactose but were successful in the case of disaccharides of trehalose type. 

The reversion products obtained when a solution of D-glucose was exposed to hydrogen chloride at 25 °C for several days included disaccharides of the trehalose type (6%), trisaccharides (4%), and oligo- and poly-saccharides (73%) the oligosaccharides are branched. Oligosaccharides and low-molecular-weight... 

In addition, the corresponding isomers with the a-glycosidic linkage are possible. The free hydroxyl group of the hemiacetal of a disaccharide cannot be assigned to a configuration the a- and /3-form are in equilibrium. The first two disaccharides listed are of the trehalose type the rest, of the maltose type. 

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