Chemoenzymatic tandem processes for the production of fine chemicals

LORENZO CERUTTI-SERRA; MARTÍN G. LÓPEZ-VIDAL; FABRIZIO POLITANO; NICOLAS ROSSI; GABRIELA OKSDATH MANSILLA; FABRICIO BISOGNO

Workshop; V Encuentro & II Workshop de la Red Argentina de Tecnología Enzimática (Red TEz); 2023

White Biotechnology have attracted great deal of attention from specialized industries like Pharma,Food, Flavor and Fragance Industries, among other. In this line, setting up tandem processesinvolving robust and highly selective biocatalytic steps in combination with non-enzymatic reactionsit?s a promising alternative to achieve shorter processing times and avoidance of solvent and energyconsuming steps related to downstream tasks.For this reason, we proposed a chemoenzymatic approach to prepare both chiral and achiral smallmolecules, that can be applied as key chemical precursors for industrial processes, taking advantageof the inherent properties of each step involved.Biotransformation had been conducted in small batches, using commercially available enzymes,immobilized ones or lyophilized preparations of E. coli overexpressing the desired enzyme. Whenpossible, reactions were carried out in one-pot, avoiding the isolation of intermediates. Theseprotocols were performed at preparative scale after optimization of experimental parameters suchas pH, temperature, co-solvent, enzyme, substrate and cofactor concentration.On one hand, we explore artificial bienzymatic cascades employing hydrolases, redox enzymes, andtransferases, such as alcohol dehydrogenases (ADHs) and ω-transaminases (TAs). We were able tosuccessfully obtain enantioenriched amines and alcohols, starting from achiral and easy-to-prepareenol esters. Compounds with one and two chiral centers were obtained with excellent yields andselectivities (up to %99 ee and de) in one-pot, one-step fashion.On the other hand, we combined biocatalysts with photoredox catalysis. This allow us to producevaluable enantioenriched halohydrins starting from racemic or achiral dihaloketones. By means ofan asymmetric carbonyl reduction, achieved by ADHs, followed by a selective photocatalytic monodebrominationreduction promoted by blue light exited flavins as photocatalyst.Additionally, we explored an alternative approach that combined light-promoted reaction withbiocatalysis. Using commercially available aromatic aldehydes as starting materials, we establisheda pinacol coupling reaction promoted by violet LED. Subsequently, a combination of biocatalysis andorganocatalysis (laccase-mediator system) was employed to oxidize the resulting diols intohydroxyketones and diketones. This two-step process effectively converted a readily available andinexpensive substrate into complex and valuable compounds with very good yields.Moreover, the combination of a biocatalytic preparation of chiral ß-hydroxy selenocyanates, followedby chemical reduction into diselenides, and then a light-promoted oxidation, gave rise to seleniumcontainingindoles. This process was initially carried out in batch, and then transferred to acontinuous flow system, reducing the reaction time from 24 h to 2 h while maintaining good yields.In conclusion, all enzymatic preparations tested proved to be good candidates in multicatalyticsystems. The combination of enzymes with different chemical methods enables the preparation ofimportant chiral alcohols and amines in an enantioenriched fashion. Finally, a continuous flowapproach is a promising option for process intensification of multicatalytic system involvingbiocatalysis.