Umpolung carbonyls enable direct allylation and olefination of carbohydrates

Mother Nature has its own arts to build a vast number of carbohydrates; however, there is still a lack of tools for selective functionalization of native carbohydrates through C─C bond formation. Such a long-standing challenge for the synthetic community lies into the intrinsic problems related to the innate properties of carbohydrates, e.g., the ease to oligomerization or polymerization, the difficulty of chemoselectivity control in the presence of multiple hydroxyl groups, the great challenge to retain the multiple chiral centers during the transformation, etc. Here, by applying an umpolung strategy of carbohydrate carbonyls, we report a direct deoxygenative allylation and olefination of carbohydrates to tackle the abovementioned issues. The reaction is compatible with a wide range of natural carbohydrates, providing a direct synthetic method to use carbohydrates as multiple C-centered chiral synthons to achieve C─C bond cross-coupling reactions. Furthermore, the synthetic applicability is demonstrated by late-stage modifications of natural products and pharmaceutical derivatives.