Selective Stereoretention of Carbohydrates upon C−C Cleavage Enabling D‐Glyceric Acid Production with High Optical Purity over a Ag/γ‐Al₂O₃ Catalyst

Abstract

Chiral carboxylic acid production from renewable biomass by chemocatalysis is vitally important for reducing our carbon footprint, but remains underdeveloped. We herein establish a strategy that make use of a stereogenic center of biomass to achieve a rare example of D‐glyceric acid production with the highest yield (86.8%) reported to date as well as an excellent ee value (>99%). Unlike traditional asymmetric catalysis, chiral catalysts/additives are not required. Ample experiments combined with quantum chemical calculations establish the origins of the stereogenic center and catalyst performances. The chirality at C4 in D‐xylose was proved to be retained and successfully delivered to C2 in D‐glyceric acid during C‐C cleavage. The remarkable cooperative‐roles of Ag+ and Ag0 in the constructed Ag/γ‐Al2O3 catalyst are disclosed as the crucial contributors. Ag+ was responsible for low‐temperature activation of D‐xylose, while Ag0 facilitated the generation of active O* from O2. Ag+ and active O* cooperatively promoted the precise cleavage of the C2‐C3 bond, and more importantly O* allowed the immediate fast oxidization of the D‐glyceraldehyde intermediate to stabilize D‐glyceric acid, thereby inhibiting the side reaction that induced racemization. This strategy makes a significant breakthrough in overcoming the limitation of poor enantioselectivity in current chemocatalytic conversion of biomass.