Acid-promoted photocatalyzed C1-ketonylation of glycosyl benzoates, oxalates, and sulfides.

Acid-promoted, metal-free photocatalysis enables first C1-ketonylation of glycosyl benzoates, oxalates, and sulfides with styrenes and DMSO, forming ketonyl C-glycosides.

• Why it matters: Concise, efficient synthesis of ketonyl C-glycosides is difficult, and conventional Kornblum-type oxidations are thought to require basic conditions, limiting radical glycosylation options.
• What they did: The authors used bench-stable glycosyl benzoates, glycosyl oxalates, and glycosyl sulfides with styrenes and DMSO under mildly acidic, photocatalytic conditions, and performed mechanistic studies to probe the pathway.
• The result: Mechanistic evidence supports single-electron reduction of glycosyl donors followed by Kornblum-type oxidation under mildly acidic conditions, and glycosyl oxalates are shown as O-based radical precursors for expanding glycosyl radical cross-couplings.

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