Highly Efficient Oxidation of Amines to Aldehydes with Flow-based Biocatalysis

A new mild and efficient process for the aqueous preparation of aldehydes, which are employed as flavour and fragrance components in food, beverage, cosmetics, as well as in pharmaceuticals, was developed using a continuous-flow approach based on an immobilised pure transaminase-packed bed reactor. HEWT, an -transaminase from the haloadapted bacterium Halomonas elongata, has been selected for its excellent stability and substrate scope. Sixteen different amines were rapidly (3-15min) oxidised to the corresponding aldehydes (90 to 99%) with only 1 to 5equivalents of sodium pyruvate. The process was fully automated, allowing for the in-line recovery of the pure aldehydes (chemical purity >99% and isolated yields above 80%), without any further work-up procedure.