Studies on the enzymatic amination of the biomass derivatives cyrene and levoglucosenone

Cyrene (dihydrolevoglucosenone, (1R,5S)-7,8-Dioxabicyclo[3.2.1]octan-2-one, 1) and Levoglucosenone (2) represent renewable platform chemicals obtained from cellulose pyrolysis and have been attracting great interest as sustainable building blocks in organic synthesis. In the frame of an Italian project (acronym: SUST-CARB), the development of original methodologies for converting these two bio-based building blocks into complex high added-value fine chemicals have been investigated. Here we report on the catalytic behaviour of three imine reductases (IREDs) and of one reductive aminase (AspRedAm) when cyrene and levoglucosenone were used as substrates in the presence of allylamine or propargylamine. Compared to the chemical reductive amination, the three IREDs displayed the same selectivity in favour of the (S)-2-amino epimer. On the contrary, AspRedAm was not selective, thus allowing to isolate the unfavoured (R)-epimer. AspRedAm and the ancillary enzyme glucose dehydrogenase were also co-immobilized on activated agarose and the performances of this heterogeneous biocatalyst have been investigated.