Photocatalytic Site‐ and Stereoselective Functionalization of Carbohydrates

Rare branched‐chain sugars represent essential structural motifs found in a wide range of biologically active natural glycans. However, efficient access to these structurally unique molecules remains a formidable challenge, whether by direct isolation from natural sources or through de novo chemical synthesis. The emergence of photocatalytic site‐selective C(sp 3 )–H functionalization has provided a revolutionary platform to tackle this long‐standing bottleneck owing to its exceptional atom and step economy as well as intrinsically mild reaction conditions. This review summarizes recent progress in the stereoselective synthesis of rare branched‐chain sugars via photocatalytic site‐ and stereoselective functionalization of carbohydrate derivatives. Particular emphasis is placed on unraveling the stereocontrol mechanisms, defining substrate scope, and showcasing the synthetic potential of these approaches for advancing carbohydrate chemistry and accelerating drug discovery.