Adsorption of a Chiral Amine on Alginate Gel Beads and Evaluation of its Efficiency as Heterogeneous Enantioselective Catalyst

Abstract

A representative Lewis base organic catalyst (9‐amino‐9‐deoxy epi‐quinine, QNA) can be adsorbed in high yields onto acidic alginate gels (AGs) using a very simple and straightforward protocol. The resulting solvogel beads (QNA@AGs) are active as heterogeneous catalysts in the addition of aldehydes to nitroalkenes, affording the corresponding adducts in good yields and moderate to excellent diastereo‐ and enantio‐selectivities. In these reactions, the carboxylic functions of the biopolymer act as both acidic co‐catalyst and non‐covalent anchoring site for the tertiary amine catalyst (as observed by IR spectroscopy). Use of heterocationic gels, derived from alkaline earth metal gels by proton exchange, provided materials with better mechanical properties and higher porosities, ultimately resulting in higher catalytic activities. This work represents the first utilization of alginates, abundant and renewable biopolymers, as gel supports/media for asymmetric organocatalytic processes.

Synthesis, Characterization, and Encapsulation of Novel Plant Growth Regulators (PGRs) in Biopolymer Matrices

“…Loading efficiency and loading capacity determination were performed to obtain information on the yield and the content of PGR in chitosan/alginate microcapsule. It is known that the entrapped amount of active agents in chitosan/alginate microcapsule depends on the type and concentration of both biopolymers, gelling cation and active agents, as well as the method of preparation [21,22]. Results listed in Table 2 show significant differences in both Encapsulation efficiency (EE) and loading capacity (LC) between samples.…”

Blue Chemistry. Marine Polysaccharide Biopolymers in Asymmetric Catalysis: Challenges and Opportunities

“…The first application of alginates in asymmetric catalysis has been recently disclosed by our laboratories. [27] Besides the use of a distinct polysaccharide, this work departs from the ones summarized in the previous subsections for two additional reasons. i) Alginate gels (aerogel and solvogel beads) were employed throughout the project, for both catalyst immobilization and enantioselective reaction.…”

Synthesis, Characterization and Encapsulation of Novel Plant Growth Regulators (PGRs) in Biopolymer Matrices

“…Loading e ciency and loading capacity determination were performed to obtain information on the yield and the content of PGR in chitosan/alginate microcapsule. It is known that the entrapped amount of active agents in chitosan/alginate microcapsule depends on the type and concentration of both biopolymers, gelling cation and active agents, as well as the method of preparation 22,23 . Results listed in Table 2 show signi cant differences in both, EE and LC between samples.…”