The synthesis of 2-deoxy-sugar containing oligosaccharides remains a formidable challenge.  One of the major difficulties associated with their construction lies in the synthesis and handling of highly unstable activated deoxy-sugar donors.    To address this problem we developed a mild dehydrative glycosylation reaction promoted by 3,3-dichloro-1,2-diphenylcyclopropene and tetrabutylammonium iodide (TBAI).  In our initial communication the yields of this reaction were generally high, however selectivity was moderate.  Based on NMR studies we have developed a second-generation dehydrative glycosylation using 3,3-dibromo-cyclopropene promoter systems.  These promoters greatly enhance both the yield and the selectivity of the reaction.  The reaction is now compatible with both armed and disarmed 2-deoxy sugar donors, and a range of acceptors.  The scope of the reaction and its application to oligosaccharide synthesis will be described.

Second-generation cyclopropenium cation promoters for highly α-selective dehydrative glycosylations with 2-deoxy-sugar donors

244th National Meeting (2012)

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