Disaccharide glycoside, synthesis

C-Glycoside synthesis via the intermolecular addition of anomeric radicals to activated alkenes has been pioneered by Giese and co-workers [120]. A wide variety of acceptors have been used in this area and both simple [131,132] and more complex (a C-disaccharide 290) [133] examples are shown (Scheme 77). 

For a previous study of glycoside synthesis using O-benzylated 2-pyridyloxy glycosyl donors in the presence of Lewis acids, see A. V. Nicolaev and N. K. Kochetkov, Use of (2-pyridyl)-2,3,4,6-O-tetra-O-benzyl-p-D-glucopyranoside in the synthesis of 1,2-cw-bound disaccharides, Isv. Akad. Nauk SSSR Ser. Khim p. 2556 (1986). 

J. Thiem, J. Schwentner, E. Schuttpelz, and J. Kopf, Synthesis, structure elucidation and conformational studies of 1 - 4-linked disaccharide glycosides, Chem. Ber., 112 (1979) 1023-1034. 

This strategy has been further extended to polymer-supported glycoside synthesis [lib], A diglycosyl fluoride attached to a PEG polymer is connected to a disaccharide by use of Cp2HfCl2 and AgOTf (Fig. 5). 

Banoub, J., Bundle, D. R. 1,2-Orthoacetate intermediates in silver trifluoromethanesulfonate promoted Koenigs-Knorr synthesis of disaccharide glycosides. Can. J. Chem. 1979, 57, 2091-2097. 

The chemistry has been extended to the preparation of a number 1,6-linked C-disaccharides. The conversion of 274 to 277 exemplihes the strength and versatility of this approach to C-glycoside synthesis. Compound 277 was converted to the 2-deoxy /8-C-disaccharide and also to the j8-C-disaccharide hy standard methods (not shown). A small library of glycal C-disaccharides was prepared by use of this novel methodology [74]. 

Synthesis of (14)-linked disaccharide glycosides of the 2,3-anhydro-4-0-(hex-2-enopyranosyl)-Q -D-allopyranoside type has been reported (Scheme 3). ... 

Preparation of Acceptor Glycosides. The acceptor glycosides can be prepared enzymatically either in separate reactions or in situ as illustrated in Table II by the p-galactosidase catalyzed synthesis of mono-and disaccharide glycosides from lactose and alcohols (25). Although not... 

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