Synthesis of C-Glycosyl Compounds

In connection with the synthesis of C-glycosyl compounds, Moffatt and coworkers182 developed the selective debenzoylation of 2,3,5-tri-0-benzoyl-/3-D-ribofuranosyl cyanide, which had been reported earlier163 reaction in methanolic ammonia-chloroform at 0° gave the crystalline 5 -0-benzoyl derivative in 83% yield, without recourse to chromatography. 

The next two chapters give the reader an excellent perspective and laboratory-proven methods for the synthesis of C-glycosyl compounds in general, and glycosylarenes in particular, utilizing free-radical reactions and Lewis acid-catalyzed oxonium ion chemistry, respectively. 

The synthesis of C-glycosyl compounds, commonly known as C-glycosides, in ionic reactions relies on the electrophilicity of the anomeric center and, therefore, involves the attack of an appropriate C-nucleophile. An umpolung method has been developed, and is described in the previous chapter. But instead of going from a carbocation to a carbanion, one can also consider homolytic or radical reactions to reverse the philicity (Scheme 1). 

Kane and Mann119 have applied selenocyclization for the synthesis of C-glycosyl compounds. Treatment of an appropriately protected ribose deriva-... 

Orsini, F, Pelizzoni, F, Synthesis of C-glycosyl compounds the reaction of acetylated glycals with fert-hutoxycarhonylmethylzinc bromide, Carbohydr. Res., 243, 183-189, 1993. 

Kozikowski, A P, Konoike, T, Ritter, A, OrganometaUics in organic synthesis. Applications of a new diorganozinc reaction to the synthesis of C-glycosyl compounds with evidence for an oxonium-ion mechanism, Carbohydr. Res., 171, 109-124, 1987. 

Kunz, H, Muller, B, Weissmuller, J, Stereoselective synthesis of C-glycosyl compounds via Michael addition of trimethylsilyl enol ethers and enamines to hex-l-enopyran-3-uloses, Carbohydr. Res., 171, 25-34, 1987. 

Grindley, T B, Wickramage, C, A novel approach to the synthesis of C-glycosyl compounds the Wittig rearrangement, J. Carbohydr. Chem., 1, 661-685, 1988. 

Nicotra, F, Panza, L, Ronchetti, F, Russo, G, Toma, L, Synthesis of C-glycosyl compounds by the Wittig iodocyclization procedure. Differences from mercuriocyclization, Carbohydr. Res., 171, 49-57, 1987. 

Witczak, Z J, Synthesis of C-glycosyl compounds and other natural-products from levoglucosenone. Pure Appl. Chem., 66, 2189-2192, 1994. 

Smoliakova IP (2000) Synthesis of C-glycosylic compounds using three-membered cyclic... 

Additions of carbon nucleophiles to enones and the consequent synthesis of C-glycosyl compounds are noted in Chapter 3,... 

Araki, Y, Endo, T, Tanji, M., Nagasawa, J., and Ishido, Y., Synthesis of C-glycosyl compounds by the addition of glycosyl radicals to olefins. Tetrahedron Lett., 28, 5853,1987. 

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