Organocatalyzed Cascade Reaction in Carbohydrate Chemistry

Institutfiir Chemie der Humboldt-Universitdt zu Berlin, Brook-Taylor-Str. 2, 

The result of this development is a constantly increasing demand for methods for the stereoselective synthesis of this class of glycosides. Although many methods exist for the synthesis of these compounds from carbohydrate derivatives or analogues [1], their applications are hampered by low yields and selectivities. This is caused by necessary complex and extensive manipulations of protective groups in combination with the activation of the anomeric carbon atom. 

The diversity of the developed glycosylation protocols is mainly driven by the different requirements of aglycons deployed, the availability of substrates and their complexity, as well as the achieved selectivities. A general solution for this synthetic 

Domino and Intramolecular Rearrangement Reactions as Advanced Synthetic Methods in Glycoscience, First Edition. Edited by Zbigniew J. Witczak and Roman Bielski. 

A big simplification of accessing C-glycosides has been achieved by reactions of unprotected and unactivated carbohydrates with phosphorylides. Examples for Wittig reactions with unprotected carbohydrates are summarized in Reference 6, whereas examples for Horner olefination (even in aqueous reaction medium) can be found in Reference 7. The reactions were carried out mostly at higher temperature. Also, allylations of even unprotected glycals have been reported in the presence of equimolar amounts of ttimethylsilyl trifluoromethanesulfonate [8]. 

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ORGANOCATALYZED CASCADE REACTION IN CARBOHYDRATE CHEMISTRY COgH... 

Chapter 2, authored by Mahrwal, deals with organocatalyzed cascade reaction strategies employed to the synthesis of important carbohydrate templates. The most efficient methodologies compiled in this review were developed before the birth of official combined domino/cascade reaction chemistry. 

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