Journal
NATURE CHEMISTRY
Volume 14, Issue 6, Pages 686-+Publisher
NATURE PORTFOLIO
DOI: 10.1038/s41557-022-00918-z
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Funding
- National Natural Science Foundation of China [21922106, 21772125]
- 1.3.5 Project for Disciplines of Excellence, West China Hospital
- National Science Foundation of the United States [CHE-1764328]
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The chemistry of carbohydrates has a long history, and a simple, stereoselective and efficient glycosylation method is still needed for studying sugars. This study presents a strategy for 1,2-cis-glycosylation without using metals or strong acids. The method activates glycosyl donors through a radical cascade, resulting in the formation of 1,2-cis-glycosides with high stereoselectivity. The reaction shows remarkable tolerance to functional groups and is applicable to a broad range of donors.
The chemistry of carbohydrates has a history of over 100 years, but simple, stereoselective and efficient glycosylation methods remain highly needed to facilitate the studies of sugars in various disciplines. Here we report a strategy for 1,2-cis-glycosylation without using metals, strong (Lewis) acids, elaborate catalysts or labile substrates. Our method operates by a unique mechanism: it activates glycosyl donors through a radical cascade rather than the conventional acid-promoted, ionic process. As elucidated by computational and experimental studies, the ally! glycosyl sulfones (as donors) form halogen bond complexes with perfluoroalkyl iodides, which-merely by visible light irradiation-fragment via radical intermediates to give the electrophilic glycosyl iodides. In situ trapping by various nucleophiles affords, in a stereoconvergent manner, the challenging 1,2-cis-glycosides. This metal- and acid-free reaction shows remarkable tolerance to functional groups. The high stereoselectivity holds for a broad array of donors. This study suggests that the simple C2-alkoxy group can serve as an effective directing group for building 1,2-cis-glycosidic bonds.
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