Glycosidation of Glycals

K. Toshima, N. Miyamoto, G. Matsuo, M. Nakata, and S. Matsumura, Environmentally compatible C-glycosidation of glycals using montmorillonite K-10, Chem. Commun., 11 (1996) 1379-1380. 

K. Toshima, T. Ishizuka, G. Matsuo, and M. Nakata, Allyl C-glycosidation of glycals mediated by DDQ, Chem. Lett., (1993) 2013-2016. 

Toshima, K, Nagai, H, Ushiki, Y, Matsumura, S, Novel glycosidations of glycals using BCI3 or BBrs as a promoter for catalytic and stereoselective syntheses of 2-deoxy-a-glycosides, Synlett, 1007-1009, 1998. 

Toshima, K, Ishizuka, T, Matsuo, G, Nakata, M, Kinoshita, M, Glycosidation of glycals by 2,3-dichloro-5,6-dicyano-/7-benzoquinone (DDQ) as a catal)4ic promoter, J. Chem. Soc. Chem. Commun., 704-706, 1993. 

J. S. Yadav, B. V. Subba Reddy, and P. K. Chand, Sc(OTf)3-catalyzed C-glycosidation of glycals A facile synthesis of allyl glycosides, glycosyl cyanides and glycosyl azides. Tetrahedron Lett, 42 (2001) 4057 059. 

The proton-catalyzed addition of alcohols to glycals is shown not to be trans diaxial addition. Bollitt et al. [83] reported that triphenylphosphine hydrobromide (TPP-HBr) was the catalyst of choice for mild and high-yield protonation and subsequent glycosidation of glycals (Fig. 5.44). 

Methyl glycosides of 2 deoxy sugars have been prepared by the acid catalyzed addition of methanol to unsaturated sugars known as glycals... 

P. Tiwari, G. Agnihotriand, and A. K. Misra, Synthesis of 2, 3-unsaturated C-glycosides by HC104-Si02 catalyzed Ferrier rearrangement of glycals, Carbohydr. Res., 340 (2005) 749-752. 

Scheme 5.63 Use of glycals in solid-phase synthesis of glycosides.

Scheme 5.64 Use of glycal methodology in the synthesis of complex C-glycosides.

C-Allyl glycosides can be prepared by the reaction of glycal epoxides with allyltributyltin in the presence of tributyltin triflate as a Lewis acid,281 and aldonitrones can be allylated with trimethylsilyl triflate as a catalyst (Equations (101) and (102)).282... 

Thus, it is of interest to generate oligosaccharides of the type C-B-A in 56, all of which are linked inter-glycosidically by a-(1->4)-bonds. We have previously synthesized various derivatives of the terminal C-B disaccharides employing the Perrier glycosylation approach (59. 60). At that same time we could combine the azide functionalization of glycals (61) with the N-iodosuccin-imide method (1 ) and develop a general approach to 3-... 

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