Evaluation of the nitroaldol reaction in the presence of metal ion-crosslinked alginates

Abstract

Calcium alginate hydrogel beads have been found to promote the Henry reaction under mild conditions.

Keratin Protein-Catalyzed Nitroaldol (Henry) Reaction and Comparison with Other Biopolymers

“…It is also worth mentioning that aliphatic aldehydes such as isobutyraldehyde were not converted (data not shown). Moreover, despite the α-helical chiral structure of the keratin, HPLC analysis of the reaction mixtures showed no enantioselection, as we have previously observed with other biocatalysts in the same reaction [19][20][21]. Although the desired β-nitroalcohols 3 were also obtained in H2O/TBAB, the reactions took two times longer than in DMSO to achieve similar conversions.…”

“…However, a gradual deactivation of the catalyst could be observed in both organic and aqueous media, although the reduction of the catalytic activity was clearly more pronounced in DMSO (Figure 1). Such behavior has also been observed with other biopolymers [19][20][21] and could be associated to loss of catalyst loading (e.g., inefficient isolation by filtration) after each The heterogeneous nature of the protein catalyst allowed its recovery from the reaction mixture and its reuse for further cycles. However, a gradual deactivation of the catalyst could be observed in both organic and aqueous media, although the reduction of the catalytic activity was clearly more pronounced in DMSO (Figure 1).…”

“…However, a gradual deactivation of the catalyst could be observed in both organic and aqueous media, although the reduction of the catalytic activity was clearly more pronounced in DMSO (Figure 1). Such behavior has also been observed with other biopolymers [19][20][21] and could be associated to loss of catalyst loading (e.g., inefficient isolation by filtration) after each cycle and/or formation of intermediate linear or cyclic aminals that could block catalytic sites of the protein. These potential competitive processes are somehow more critical in DMSO than in aqueous solution; however, the reasons behind these differences remain unclear.…”

“…On the other hand, the nitroaldol (Henry) reaction is a highly versatile C-C bond-forming reaction between an aldehyde or ketone and a nitroalkane to yield β-nitroalcohols, which can be easily modified into valuable building blocks [13][14][15][16][17]. As part of one of our research programs devoted to understanding the potential catalytic role of different biopolymers [18][19][20][21], we report here for the first time the catalytic properties of keratin protein towards the nitroaldol (Henry) reaction as well as a critical comparison with the performance of other natural polymers in the same process.…”

“…As part of one of our research programs devoted to understanding the potential catalytic role of different biopolymers [18][19][20][21], we report here for the first time the catalytic properties of keratin protein towards the nitroaldol (Henry) reaction as well as a critical comparison with the performance of other natural polymers in the same process.…”