Blue Chemistry. Marine Polysaccharide Biopolymers in Asymmetric Catalysis: Challenges and Opportunities
Alginate, chitin (precursor of chitosan) and carrageenan are natural polysaccharides derived from marine sources and available in nearly unlimited amounts. In contrast with other natural polysaccharides (i.e. cellulose), their monomers bear functional groups (amine, carboxylate, sulfate). These functional groups can be used to anchor catalytic species, or even as catalytically active units. In this mini-review, the utilization of marine polysaccharides in asymmetric catalysis is discussed. Examples include: i) combinations with chiral catalysts, resulting in heterogeneous catalytic systems, and ii) utilization of the biopolymers as chirality inducing elements serving as chiral ligands or organocatalysts. The reviewed works propose innovative and unconventional utilizations of these renewable materials, providing not only a useful alternative to oil-based polymers, but also unforeseen and fascinating opportunities in the field of asymmetric catalysis.