Reductive Ring-Opening in Domino Reactions of Carbohydrates

REDUCTIVE RING-OPENING IN DOMINO REACTIONS OF CARBOHYDRATES 

Raquel G. Soengas, Sara M. Tome, and Artur M. S. Silva 

Department of Chemistry QOPNA, University ofAveiro, 3810-193 Aveiro, Portugal 

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

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Our aim in this chapter is to present the most important advances in the domino reactions of carbohydrates based on the metal-promoted ring opening of cyclic sugars. These procedures, promoted by different low-valent organometaUic reagents, start with the addition of the metal to an electrophihc site (i.e., an alkyl hahde, a carbonyl, an alkene, or an alkyne), followed by reductive ehmination to the open-chain sugar. From this open-chain sugar intermediate, the next reaction takes place under the same reaction conditions. 

The Bernet-Vasella reductive ring opening has found many applications in carbohydrate chemistry and is a key step in several natural product synthesis [25,26]. However, the instability of the liberated aldehyde can be a problem, leading to side reactions and decomposition [27,28]. To overcome this limitation, the aldehyde has been trapped in situ by nitrogen or carbon nucleophiles. As a result, a series of domino reactions based on the Bernet-Vasella reaction has been described and applied to the total synthesis of chemically and biologically relevant products. 

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