D-Excess-LaA Production Directly from Biomass by Trivalent Yttrium Species

• Published in: iScience 2019-02, Vol.12, p.132-140
• Main Authors: Xu, Shuguang, Li, Jing, Li, Jianmei, Wu, Yi, Xiao, Yuan, Hu, Changwei
• Format: Article
• Language: English
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2019.01.008

D-lactic acid (D-LaA) synthesis directly from actual biomass via chemocatalytic conversion has shown high potential for satisfying its enormous demand in widespread applications. Here we report yttrium (Y(III))-species-catalyzed conversion of xylose and raw lignocelluloses to LaA with the highest yield of 87.3% (20% ee to D-LaA, ee%=(moles of D-LaA - moles of L-LaA)/(moles of D-LaA + moles of L-LaA) × 100). Combining experiments with theoretical modeling, we reveal that [Y(OH) (H O) ] is the possible catalytically active species, enabling the unconventional cleavage of C3-C4 in xylulose and the subsequent dehydration of glyceraldehyde to pyruvaldehyde (PRA). The distinct interactions between hydrated-PRA and [Y(OH) (H O) ] species contribute to the formation of different enantiomers, wherein H-migration via re-face attack leads to L-LaA and that via si-face attack yields D-LaA. The lower strain energy barrier is the origin of excess D-enantiomer formation.