D-Glucose Isomerization with PAMAM Dendrimers as Environmentally Friendly Catalysts

The isomerization of D-glucose to D-fructose plays a key role in the biochemical and chemical conversion of biomass, and it is therefore desirable to develop and improve catalysts for this reaction. In this study, the environmentally friendly polymer poly(amidoamine) (PAMAM) dendrimer's properties as catalysts for this isomerization are investigated. The experimental results showed that the PAMAM dendrimers, which have basic terminal groups, can effectively promote the D-glucose isomerization reaction. Under the optimized reaction conditions, D-fructose was generated with a 20% maximum yield and above 90% selectivity. C-13 and H-2 isotope experiments by NMR were carried out to explore the reaction mechanism. When the reaction was performed in D2O, the C-1 signal of D-fructose changed to a triplet, which confirmed that the C-1 carbon binds to a deuterium atom, i.e., isotopic exchange. It was also found that the deuterium atom at the C-2 position of D-glucose-2-d(1) cannot transfer to D-fructose. These data indicate that PAMAM dendrimers catalyze D-glucose isomerization through a mechanism, which includes deprotonation, formation of ene-diol intermediate, and proton exchange with the solvent.

Automated summary

The study demonstrates that PAMAM dendrimers serve as effective catalysts for the isomerization of D-glucose, with experiments and isotope experiments revealing the reaction mechanism.