Biocatalytic reactions have been developed to make organic syntheses more efficient and environmentally friendly. Several attributes as the stereo-, chemo- and regioselectivity can be highlighted in the application of enzymes or cells as catalysts to produce alkaloids with high enantiomeric purity, which is important because the chiral centers, generally, define the biological activities of alkaloids. In this context, we proposed the synthesis of pyrrolizidine scaffold by multi enzymatic cascade reaction using transaminases (TA) and Imino reductases (IRED). In this poster, it was reported the synthesizes of two furans derived carbonyl compounds that were employed as substrates in the first step of the multi enzymatic cascade, where stereoselective transaminase performed reductive amination on the less hindered ketone, then a spontaneous cyclization led to enantiopure pyrrolines with conversions up to > 99% and enantiomeric excess up to > 99% ee. 24 commercial TA were evaluated to optimize the first step of the biocatalytic reaction. In addition, a chemoenzymatic reaction with TA and ammonia borane was performed to obtain pyrrolizidine alkaloids in a one-pot process. Finally, enantiopure pyrrolines were produced from a furan derived carbonyl compounds using 4 commercial transaminases with excellent stereo- and regioselectivity. These promissory results are the first step of the multi-enzymatic cascade process involving TA and IRED.

Biocatalysis: Asymmetric synthesis of pyrrolizidine alkaloids

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