Glycals rearrangement

Clearly compound 26 (R = Ac) had undergone a reaction analogous to the glycal rearrangement. It has been demonstrated that the rearrangement of this compound also occurs at room temperature in acetic anyhydride in the presence of zinc chloride (34). Under these conditions, however, a further slower isomerization takes place and a third product, assigned the acetylated enone-hydrate structure 29, was isolated. As noted later this structure has been shown to be incorrect. 

E. Wieczorek and J. Thiem, Preparation of modified glycosyl glycerol derivatives by glycal rearrangement, Carbohydr. Res., 307 (1998) 263-270. 

Reactions Involving 2,3-Unsaturated Saccharide-to-Glycal and Glycal-to-Glycal Rearrangements... 

Epierythromycin A has been synthesized from a desosaminyl erythronolide precursor using the glycal rearrangement glycosylation procedure with a glycal obtained from cladinose. ... 

Perrier RJ (2001) Substitution-with-Allylic-Rearrangement Reactions of Glycal Derivatives. 215 153-175... 

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. 

Tochtermann reported the addition of dichlorocarbene to the racemic glycal 52, whose cyclopropyl-allyl rearrangement leads to the 2//-pyran. The synthesis of the optically pure (+)-(2S,3R,7S) and (-)-(2f ,3S,7f )-glycal precursors has also been achieved. As pointed out, optically pure glycals are versatile precursors for carbohydrate synthesis <00EJO1741>. 

Glycals can be glycosylated not only directly via electrophilic addition, cyclo addition, nucleophilic addition and rearrangement reactions but also indirectly by conversion into a range of other glycosyl donors. One of the most important classes of these glycal-derived donors, the 1,2-anhydro sugars, is discussed in detail in Section 1.3. 

By spontaneous sigmatropic rearrangement of the glycal 3-trichloroacetimidate made with NaH, CI3CCN,... 

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