Room-temperature synthesis of 3-keto-C-disaccharides from unprotected glycal donor via palladium-catalysed Heck-type reaction

We report a practical and efficient method for synthesizing 3-keto-C-disaccharides via a palladium(0)-catalyzed Heck-type reaction followed by keto-enol tautomerization. This transformation utilizes unprotected glycals and 2-iodoglycals as substrates and proceeds under mild, room-temperature conditions with Pd(OAc)2 as the catalyst. Notably, this is the first example of a Heck-type C-glycosylation involving unprotected glycal donors. The reaction exhibits regioselective ketonisation and excellent stereoselectivity, showcasing a broad substrate scope that includes D-glucal, D-galactal, L-rhamnal, and D-xylal. The desired 3-keto-C-disaccharides are obtained in good to excellent yields. This strategy provides a valuable platform for constructing structurally defined C-linked disaccharides, with potential applications in carbohydrate-based molecular design.