N-Heterocyclic Carbene-Catalyzed Transformation of Formyl Sugars to Deoxy-Sugar Lactones

The role of N-heterocyclic carbenes (NHCs) in catalyzing the transformation of sugar aldehydes into deoxy-sugar lactones has been systematically investigated. Imidazolium-derived NHCs efficiently facilitated the conversion of both pyranose- and furanose-based sugar aldehydes through the formation of Breslow intermediates, offering a mechanistically distinct and stereoselective pathway. The methodology demonstrates operational simplicity and excellent functional group tolerance, accommodating ester, ether, silyl, and acetonide protecting groups. This versatile approach broadens the synthetic utility of sugar aldehydes by providing access to structurally diverse sugar lactones, which are valuable in carbohydrate chemistry and bioorganic applications.