Unprotected glycoside

The reactions of tributylstannyl ethers and dibutylstannylene acetals of diols or polyols containing one hydroxyl group that is at the end of a chain (terminal diols) are listed in Table IX. Some reactions on compounds of this type, primarily unprotected glycosides, have been discussed earlier, but for those examples, the terminal hydroxyl group was not critical in... 

Fig. 61.—Formation of a (1 — 6)-linked disaccharide by reaction of a dibutylstannylene acetals of unprotected glycosides with a glycosyl bromide.349...

A very selective method of oxidizing secondary alcohols is bromino-lysis of tributyltin ethers prepared by the treatment of hydroxy compounds with bis(tributyl)tin oxide. The reaction is regio- and stereospecific and is an important means of oxidizing unprotected glycosides [734]. 

Optimum conditions for the electro-oxidation of l,2 5,6-di-Q-isopropylidene-a-D-glucofuranose to the corresponding 3-uIose have been developed In a study of the hydration of methyl 4,6-0-benzylidene-2-bromo- and 2-chloro-2-deo) -a- and -D-xvlo-hexopvranosid-3-ulose in acetone solution, only the fl-D-xylo-derivatives were observed to hydrate and in another investigation the isomeric composition of freshly prepared D-ribo-hexos-3-ulose in DjO has been examined by H-n.m.r. spectroscopy. Full details have been published on the regioselective monooxidation of unprotected glycosides by reaction of Q-stannyl derivatives with bromine. ... 

Extensive work has been done by using buta-l,3-dienyl-glycosides of unprotected sugar to study aqueous Diels-Alder reactions and to prepare optically active oligosaccharides [20]. 

K. Toshima, Y. Ushiki, G. Matsuo, and S. Matsumura, Environmentally benign aryl C-glycosidations of unprotected sugars using montmorillonite K-10 as a solid acid, Tetrahedron Lett., 38 (1997) 7375-7378. 

In carbohydrate chemistry, the preparation of ethers that are stable in the presence of acids, bases, and aqueous alkali is an important analytical and synthetic tool. The methods used for the etherification of hydroxyl groups51 generally employ reactions of unprotected sugars and glycosides with methyl, allyl, benzyl, triphenylmethyl, and alkylsilyl halides in the presence of a variety of aqueous and nonaqueous bases. 

For the mono-C-glycosylphenol, the commercially available 2,4,6-trihydroxyacetophe-none was chosen and selectively methylated at C-2 and C-4. The partially protected phenol was glycosylated with the C-benzyl-protected glucosyl trichloroacetimidate in the presence of trimethylsilyl triflate as promoter to give directly a C-(benzyl protected)glycosylphenol. The unprotected hydroxyl group of this compound was converted with benzoyl chloride into a fully protected C-glycoside phenol. Treatment of the benzoate derivative with sodium hydroxide in... 

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