Nanocellulose enriches enantiomers in asymmetric aldol reactions

Abstract

Catalytically inactive cellulose nanofibers with crystalline solid surfaces enhance highly enantioselective organocatalysis at the interface in proline-mediated aldol reactions.

Inherently Distinctive Potentialities and Uses of Nanocellulose Based on its Nanoarchitecture

“…Further evidence for the involvement of nanocellulose in the preferential orientation of transition states was provided by quantum mechanics/molecular mechanics/steered molecular dynamics (QM/MM-SMD) in the a b c proline-catalyzed aldol reaction at the surfaces of TOCNFs (Fig. 4c; Ranaivoarimanana et al 2020). The catalysis of the reaction between aromatic aldehydes and cyclopentanone by (S)-proline on the hydrophobic (100)/( 200) crystalline surface of the nanocellulose delivered products with a high enantiomeric ratio (up to 89% ee, syn form).…”

“…Nevertheless, it should be noted that the surface order provided by the crystalline nanocellulose, and the enhanced cooperativity-which are the key factors in superior catalytic activity in such aldol reactions-can overcome the solventrelated issues. In fact, various methods such as solvent exchange by dialysis or centrifugation are known to produce stable organogels that are suitable for use in the reactions mentioned above Jones 2019, 2020;Ranaivoarimanana et al 2019Ranaivoarimanana et al , 2020. Finally, nanofibers of other structural polysaccharides, such as chitosan, are expected to demonstrate unique catalytic behaviors, such as highly selective Knoevenagel condensations under green solvents (Hirayama et al 2020).…”

Nanocellulose: Beyond the ordinary

“…In particular, metal (e.g., Pt, Pd, Ru, Ag, and Au) nanoparticles deposited on the surfaces of nanocellulose have been successfully used in various catalytic reactions (Kaushik and Moores 2016); however, nanocellulose itself in metal-organic composites cannot play a starring role in catalysis. By contrast, several challenges in interfacial catalysis using nanocellulose have recently been reported, including chirality-specific hydrolysis of amino acids, highly efficient acetal hydrolysis, enantioselective hydrogenation of aromatic carbonyls, and enhanced proline-mediated organocatalysis with high enantioselectivity (Ranaivoarimanana et al 2020). Nanocellulose has a regular alignment of chiral structures and an amphiphilic nature of its surface, and these will affect the fate of interfacial catalysis in stereochemistry, with expectations for the future.…”

Anl-proline-modified chiral porous hyper-crosslinkedl-phenylalanine dipeptide—increased reaction rate and selectivity in asymmetric catalysis

“…Moreover, l -Pro can also be used to catalyze Michael, Diels–Alder, and Robinson cyclization reactions. 12–14…”

“…Moreover, L-Pro can also be used to catalyze Michael, Diels-Alder, and Robinson cyclization reactions. [12][13][14] The L-phenylalanine dipeptide (L-Phe-L-Phe-OMe) is a chiral inducer with a loose spatial structure, which can form synergistic interactions with proline residues to effectively improve the enantioselectivity of the product. 15 Therefore, grafting proline with peptides can be an effective means for the syn-thesis of efficient chiral catalysts.…”