Chemo-enzymatic cascade reactions

The concept of artificial metaUoenzymes displays attractive features for both biocatalysis and chemocatalysis precious metal reactivity, genetic optimization potential, and well-defined second coordination sphere provided by a protein scaffold. Such scaffolds are further tunable by mutagenesis and can be used as linkers for immobilization strategies. 

The selective catalytic hydrogenation of dihydrojasmone, performed by applying Rh on charcoal and CS2CO3 as an additive base in a continuous flow reactor, gave quantitative conversion to the product with 93% cis selectivity. The reaction was executed in n-heptane at 30 °C and up to a substrate concentration of 0.5 M. The solvent stream containing the hydrogenated product was used either 

---

Scheme 3.18 Conceptual view of chemo-enzymatic cascade reactions mediated by artificial...

Chemo-Enzymatic Cascade Reactions for the Synthesis of C lycoco n j ugates... 

I 6 Chemo-Enzymatic Cascade Reactions jor the Synthesis of Glycoconjugates... 

Unnatural nucleotide sugars are interesting compounds as novel substrates for GTs in tasks like glycan-specific nonradioactive labeling. Biotin-derivatives of UDP-Gal/-GalNAc derivatives were synthesized with a chemo-enzymatic cascade reaction (Figure 6.3) [83, 84]. 

I 6 Chemo-EnzYmatic Cascade Reactions for tine Synthesis of Clycoconjugates... 

Simons, C., Hanefeld, U., Arends, I., Sheldon, R. A. and Maschmeyer, T. Towards genuine cascade reactions asymmetric synthesis using combined chemo-enzymatic catalysts, Top. Catal., in press. 

Simons C, Hanefeld U, Arends IWCE, et al. Towards catalytic cascade reactions asymmetric synthesis nsing combined chemo-enzymatic catalysts. Topics in Catalysis... 

Starting from UDP-Glc/UDP-GlcNAc biocatalytic epimerization and oxidation were combined with chemical hydrazone formation. These simultaneously occurring steps may be also classified as chemo-enzymatic one-pot cascade reaction. 

Figure 6.3 Cascade reaction for the chemo-enzymatic synthesis of biotinylated UDP-Cal and UDP-GalNAc. (a) UDP-Glc(NAc)-4 -epimerase, (b) galactose oxidase, (c) catalase, (d)...

In this chapter, we have summarized striking examples of cascade reactions for the chemo-enzymatic synthesis of glycoconjugates. The benefit of cascade reactions without intermediate product work-up is emerging in the field of glycan synthesis. Future studies should be therefore directed toward biocatalyst engineering and process design to match the requirements for sequential, one-pot, and convergent cascade reactions. 

---