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

Shuguang Xu; Jing Li; Jianmei Li; Yi Wu; Yuan Xiao; Changwei Hu

doi:10.1016/j.isci.2019.01.008

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

iScience. 2019 Feb 22:12:132-140. doi: 10.1016/j.isci.2019.01.008. Epub 2019 Jan 10.

Authors

Shuguang Xu¹, Jing Li¹, Jianmei Li², Yi Wu¹, Yuan Xiao¹, Changwei Hu³

Affiliations

¹ Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, PR China.
² Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, PR China. Electronic address: lijianmei@scu.edu.cn.
³ Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, PR China. Electronic address: changweihu@scu.edu.cn.

Abstract

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)₂(H₂O)₂]⁺ 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)₂(H₂O)₂]⁺ 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.

Keywords: Biomaterials; Catalysis; Chemistry.